I like to imagine that as soon as we discover FTL and break spacetime, the simulation crashes and the higher beings are annoyed they have another bug to fix
“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.” ― Douglas Adams, The Restaurant at the End of the Universe
human scientists are the higher beings who put a sim into effect at a higher speed than their own reality to see the future, then when paradoxes occur, they have to wind back to when it happens, and figure out what's meant to happen then, and to do that they have to study the sciences which the sim people developed, but they can't figure it out, so one frustrated technician just removes the people who did the faster than light stuff, and resumes the sim.
Our physical bodies live in physical dimension out of many. ⚡️⚡️⚡️In multi-dimensions existence, causality wouldn’t be violated. Abrahamic secret texts of Jews, Christians & Muslims have hinted that “instantaneous” travel is indeed possible if we live within multiple dimensions. Each dimension has its own speed limit. When u reach certain speed, u jump into a deferent dimension & u loose direct connection to ur initial one until u slow down to within its speed limit. 🤔
I mean, on a certain level it's completely intuitive. You can't shine a light at something and then arrive before the light hits it, or conversely the light we see from stars has been traveling X light years to reach us, so to travel faster than light we would travel to the source before it was sent. But I will agree that it's crazy that we have actual equations and models for it, thanks to the work of giants (upon whose shoulders we stand).
If you think about it, maybe it is just a breach of the time line where earth after the ship send the reply to turn off the ftl transmitter, so you have a time line where the crew reply and a other where the don't receive any message because earth did not send it. So in the end 2 time line exist and no loop or paradox.
That’s what I think, I have this the universe doesn’t give a shit theory, sort of like if a ball went into a time travel wormhole and out the other end and knocked itself out of the way well then you would just have two balls because the universe doesn’t give a shit.
Ummm ok ??? am I supposed to be like impressed at how smart you think you are or something???? Like it was just an idea I had I don’t even know if I’m right, I’m probably not but I can admit that because I’m not you know…..up my own ass ?
There once was a young lad named Mike. Who could run faster than the speed of light. He took off one day, In a relative way, And returned on the previous night!
Well, I don't know about time travel, but a fascinating thing to think about is that if you could travel FTL and have a way to look at earth from any distance, you could go far enough away from earth to see the past.
@@rodrigues.iVery easy point to understand. We're here on Earth looking out into space. If we look at the sun we're all seeing the sun in the past, as it was 8 minutes ago because that's how long light from the sun takes to reach our eyes. So likewise, if we could instantly transport to a point next to the sun and then looked at Earth we'd be seeing Earth as it was 8 minutes ago in the past. If we could instantly transport to Alpha Centauri and stare back at Earth we'd be seeing Earth as it was over 4 years ago because that's how long it takes light to reach our eyes from that star system. Get it?
@@Yourmomh0u5e If you mean me, how exactly is it wrong? If you move at FTL speeds you would see 'old' light once you stopped, therefore you would see the 'past' of the planet, which is why we see stars not as they are, but as they were many years ago, some stars already died, but we still see them because they're so far away that light from the time of their death has yet to reach us, same way we see planets, which reflect the light from stars. Light speed isn't instant, it's just really really fast. Thats what Lightyears are, we see a star 1 lightyear away as what it was like 1 year ago, because that's how long it takes for light to travel to our visible space. If I'm wrong, feel free to correct me, I am not omniscient, I can make mistakes, but I don't think I did here.
@@paulshlasko3608 No, because as you would get closer to earth you would see less and less into the past, @philgiffin1487 explained it perfectly, the closer you are to a planet the less the time difference would become. I explained it in my other reply more thoroughly.
"It almost seems like a cruel cosmic joke that the universe be arranged such a way that we are able to look out and glimpse its wonders and yet are trapped here by the speed of light." So well said
It is only a cruel joke, due to human avarice. The concept of continuing to climb stairs to silver level, gold level, platinum level, diamond level luxury and status ...and be temtped by yet another staircase. The fire door locks behind you and you're trapped on a dirty roof with a noisy AC compressor.
Let's adopt Asimov's interpretation and say that light, gravity, and causality all travel at "Celeritas", a special speed that is an innate property of the universe.
And the speed of light is a top limit in the Lorentz transformation of spacetime diagrams that cannot be exceeded ! Using FTL info transmission breaks the maths of the spacetime diagrams (square roots of negative numbers), so the conclusions of this videos do not stand :)
@@CoolWorldsLab light travels faster than sound and doesn't break casuality for a blind man. Light travelling faster than light doesn't break casuality either. The universe operates on universal time, not local time. If you want to do a video about casuality, do one on the two different speeds of sound on Mars.
I like Jim Butcher's version Law For the Conservation of History. Postulating that there is a force similar to inertia for temporal events. Essentially after an event has occurred a strong force will ensure that it remains unchanged
Yeah it might be a bit naive or misunderstanding some implications of our current understanding of quantum mechanics, but it always seemed more intuitive to me that the future is set and that "change" is just a matter of viewing the universe from a different position within the spacetime and there is no need to "invent" a force preventing causality to break when the universe was already set (though this being true would probably make closed causal loops impossible).
In the Halo extended lore (books and etc), their use of slipspace creates time paradoxes like, constantly. It's not uncommon for a ship to arrive at it's destination hours, days, or WEEKS before it left. And everyone's collective reaction to the existence of these paradoxes is just to kinda shrug, say "hey man, don't worry about it too much," and move on
Every time I learn something about Halo lore it sounds completely tonally dissonant from the games I played. "John Halo is a brainwashed child soldier alongside every other Spartan, and the people who commissioned the Spartan Project belong in the Hague." "The use of slipspace at all is an existential threat to all the universe." "the UN created the Spartans to suppress rebellions with legitimate grievances" this is a space marine game about fighting aliens and being badass, what the fuck is all this genuinely horrifying secondary lore?
@@nickmalachai2227 I'm glad to see someone else say this, I feel basically the same way. The deep lore fans irk me bad, it just sucks all the wind out of the sails for one of the most fun series of games I played as a kid. Like, I actually used to enjoy wiki diving and reading some of that lore- some of it was cool- but then every time I see people get up on a pedestal about how the UNSC are some evil Nazi-equivalent authoritarian regime, "the real baddies" (Compared to the Covenant? Those genocidal maniacs? Seriously?) and the spartan child soldier stuff, it makes it feel like none of it was worth it. Like, way to ruin a series; not only are the games after Bungie moved on arguably kind of mediocre, but then the books and other secondary lore retroactively hurt the Bungie games too. There's just nothing left to enjoy. It makes me so sad.
@@HorseDe-luxe I actually like the secondary lore, for the most part, I just wish the games were tonally consistent with it. Granted, I'm a Star Wars and Transformers fan. I'm used to worse bullshit than this.
I've thought for a some time that traveling faster than light would be totally pointless, since traveling AT the speed of light would not only get you anywhere instantly, but would take you everywhere simultaneously before a moment passes. Why go faster? You would arrive before you departed. However, this is clearly necessary to overcome the effects of time dilation if you want to be able to return to your home frame of reference. You'd need to travel just faster than the speed of light enough to arrive at the same moment you departed. Teleport. Never mind that this would require enough energy to essentially make the universe run backwards. It's what he explains around 14:30 that is so insightful. Serious confusion arises if you fail to keep your frames of reference distinct when applying time dilation, and as he points out, you must remember that the speed of light is the same in all frames of reference. Both time and space will bend to accommodate it's constancy. While the rate of the passage of time is determined by velocity, we don't actually have any idea what our true velocity is, as we have nothing to compare the universe (results of the big bang) to. We can no better know what the universal time constant is than we can know where we are in existence. While this places limits on what we can know about time, the fact that the future occurs first for those traveling relatively faster indicates that time is not an integral property of matter, but some kind of overlay that matter checks in with. Travel fast enough and you'll stop checking in.
Omg this diagram finally explained why and how space and time are connected. Thank you so much. I always thought I understood this concept but I was just repeating info not fully grasping it.
@@N3KRoM3KHANIKaL Yes, I completely agree. We do not have enough information and may never get it. And relying only on math is most likely not the answer. It's a very "human" way of trying to solve things.
Even then it's still a massive stretch, we don't even know it time is linear, parallel, or circular, we can observe evidence of what we experience as the passing of time, but quantum physics seems to be bending our undersanding of the rules of time, energy and matter. Remember 3rd law of thermodynamics, entropy "TENDS", why the word tend? Because at this point it is outside the realm of our current paradigm of awareness as well as the technological capabilities as it relates to se sensory data acquisition to be able to define that theory with a more resolute likely useful definition. Aka our current level of understanding is the first black and white television. Imagine, give it colour and increase its resolution to 8k, I'll bet its a picture you can draw a more detailed understanding from. Crude metaphore I know, but there is no such thing as the best answer, only the "currently knowable" best answer. Don't act like it's a doorway to a new world of understanding, but all the knowledge you learn is simple a small stepping stone for you to leap from into the universe of the unknown, for the purpose of stumbling upon new unseen, unknown, and untouched wonders. Big and small. Seen and currently unseeable. The final frontier is not the beginning of the last mission, but the beginning of the first mission, that never ends.
@@N3KRoM3KHANIKaL maybe so.. but that doesn’t mean we give up trying. Ever. The only real failure that exists is in not trying at all. Otherwise every attempt to find FTL or unlock the mysteries of the universe bears fruit in the end, even if ultimately that fruit is just another way in which we learned how not to make a lightbulb.
Hiya, aerospace engineering grad student here! This seems really well-researched, and yes, this _is_ an effect that happens exactly as you say - and it's also not time travel. Not in the way we conventionally think of it, anyway. This model is actually referring to _information_ travel, which is surprisingly pretty different! And no, even if you switched the FTL signal to, say, a person traveling FTL to tell the Vegans (lol vegans XD), everything still holds up to how we understand relativity. This is because this thought experiment doesn't factor in the *quantum effects of information.* Take a pair of electrons, for example - let's make these two electrons quantum-entangled (something that can actually happen!), which is a fancy way of saying that their properties are connected and shared - when one electron does something, so does the other. We have experimentally proven that, when one electron's spin flips, so does the other - _instantaneously._ Which shouldn't be possible, so long as we assume everything is capped at the speed of light. AND this happens regardless of the electron pair's distance from one another. So in theory, if we separated these two entangled electrons across the entire Milky Way, then flipped one, the other would also flip at the exact same moment as the first. This is because with _information_ travel, there's no light-speed limit to be found - no speed limit at all, really. So when one electron flips, the information of that flip _instantly_ travels to the other electron, and so it flips at the exact same time. Crazy, right? All this just to say that, according to quantum physics, information is not bound to the rules of relativity, in regards to both space AND time. This is exactly what happens in this thought experiment - due to the nature of the different axes of space, the information onboard the STL ship comes in all jumbled and in the wrong order, but because information doesn't actually have a given speed limit (the entangled electrons are proof of this), nothing in relativity is broken! The rest of the universe follows the horizontal axis (mostly), and causality remains unbroken - since the space axis is relative to the observer, the *perspective of the order of events can change* because _information has no given speed limit,_ it's only limited by how it's perceived - so the events themselves still happen exactly in the order they happen. The line parallel with the space axis, traveling up and down, is really an _information perception line._ Think about it this way - forget the signal. What if you had a ship that traveled at exactly the speed of light? Both its time and space axis would be at 45 degrees, and thus its perception line would also be at 45 degrees. In that frame of reference, all three events - supernova X, Earth observation of X, and Vega observation of X - would happen at the exact same time. And what if we add back in the signal, and the ship was an FTL ship? Flip the STL ship line and the STL space axis line at 14:47, and we're FTL! The perceived (note: _perceived_ ) order gets _really_ janky with this example - first, the Vegans receive the warning from Earth; then the Vegans see X; then Earth sees X; then X happens. It's almost backwards! But that's okay, because *information - and thus our perception of that information - can arrive in whatever order it wants, or rather, in the order that the frame of reference allows.* No time travel, just information travel. Just thought I should mention that, to alleviate the confusion! Physics, sadly, just _really_ doesn't like actual, real time travel. (My inner Doctor Who fan is crying) Edit: Whoopsie, so I brought this post by my thesis advisor, aaand turns out I may be just a _wee_ bit absolutely incorrect about how transmission of information via quantum entanglement works. Say you have a pair of entangled electrons that you've measured to have a net spin of 0. If you measure one electron's spin to be some value x, due to quantum entanglement, the other electron's spin must be -x. Simple enough, right? All entanglement says is that mutually shared info is conserved. _Technically_ it means you also instantly know that the other electron's spin is some value -x once you measure the first electron to be spin x, but the pitfall for many people (including myself, sadly) is extending this logic to the _transmission_ of information. Just because an electron is entangled with another doesn't mean flipping that electron will have an instant effect on the other. Transmission of information is, much like everything else in the universe, bound to the speed of light. Physically flip an electron, and the other electron will flip after an appropriate amount of time, NOT instantly. (Note that this also is in an ideal setting, where spin only happens along a single axis - normal electrons can have spin along any axis they want, which has all sorts of brain-breaking issues that I will NOT try and summarize for both your and my sanity.) Having said that, though, the logic of the information perception line still holds true to a degree. Proper FTL travel doesn't yet exist, so we can't properly test the effects that FTL might have on causality. The thought experiment proposed in this video calls into question some of the issues FTL might have, but this post is more calling into question the claim that what's happening is time travel. An error I made was assuming the information in this setting was quantum information, which makes no sense since this isn't really a quantum system! You find quantum info in a quantum system, which this isn't, so the information perception line is really just the perception of normal, tangible information. (And again, quantum info like everything else is bound to the speed of light. Just pointing out another error I made.) And yes, it still looks like causality is being broken, but still only from an information standpoint. Events still carry on as they do, it's just the order of _detection_ of events that's getting weird. Which is totally fine! Harking back to the entangled electrons, if we separate the pair far enough and make enough observations in a second, communication via the speed of light would take longer than the interval between observations, meaning you can find out the other entangled electron's spin faster than the other side could tell you what that spin is. So in a bit of a backwards way to what I said earlier, information _still_ finds cheeky ways of "beating" the speed of light without actually beating the speed of light. If information can do that, then there's no reason why this doesn't extend further ie. to this thought experiment. Information gets wonky, but we already know that's okay. No time paradoxes here! To be fully honest here, I ain't an expert in this field - I'm a hands-on build stuff kinda guy, the stuff discussed in both what I've said as well as in this video are only tangentially related to what I study. Thanks so much to all the people who've (politely) criticized my errors - y'all were the reason why I brought this to my thesis advisor in the first place. Science is all about correcting incorrect assumptions, so thanks to all of y'all for setting me straight! And feel free to point out any other errors I've made in this edit - there's only so far proofreading will get you lol
I wanted to write something similar, but you explained it much better than I ever could. TLDR: Paradoxons are always a human brain child. If they actually happen they are resolved on their own.
This implies a device can be constructed to determine absolute speed of an object. The idea of an information order can be used to distinguish the angle of a given objects space axis and the information axis. Take two ships in space, they start off docked, moving through space at some unknown fraction of the speed of light. they exchange entangled electrons and set timers for an hour. both ships then accelerate away from one another so their separation speed is .5c after an hour of observed time on one ship they flip their electron, but the on the other ship they see the electron has already flipped. they can conclude that because the electron flipped on their ship, they must have been moving at a higher lower angle to the information plane. Assuming they can observe and be alerted to the flip as you suggest, they could even calculate their angle to the information plane. Now lets say after each ship observed an hour pass they turned around and reunited. After their rendezvous they will be on the same course and speed as before but now know what that speed is compared to the information plane. They can then decelerate together to be at zero absolute universal speed. At this point our duo can do all kinds of naughty things like shine around the emittance spectrum of helium at any other observers in the universe while transmitting a signal declaring their speed as zero absolute. Of course this would allow any observer to determine their absolute speed by comparing red shift of the helium spectrum. Or our stationary ships could observe the redshift of equidistant galaxies billions of light years away and determine were the center of the universe is. The ability to take such actions is highly cursed and Einstein would not approve. The fundamental problem here is the information axis. The universe does not actually suffer this problem or we would have declared Einstein's theory of relativity dead the moment QE electrons were observed. With accurate enough clocks we could have already determined the absolute speed of earth by using earth's rotation to generate the velocity difference. The flawed assumption here is that QE can relocate information. QE cannot do this. Yes, the changes in a particles are instant BUT you could not differentiate the change from random chance without observing BOTH particles and comparing the results. So far as we know this observation must happen at luminal speeds. Example: some process, call it radioactive decay, simultaneously generates two entangled electrons. these electrons have an a spin sum of zero but each one has an unknown spin. you then separate these electrons from each other. you take one electron and put it threw some spin flipping machine. Now you pass your electron through a filter that sends an electron with an up spin into detector A and a down spin electron into detector B. The moment the electron hits a detector it breaks its entanglement due to the act of observation. if your electron hits the up spin detector you can know with certainty the other electron would have hit the down spin detector but the observer of the other electron would have no clue your electron was passed through the flipping machine unless you told them. Fundamentally the information of the spin the electron does not exist until observed, changing the spin state before hand changes nothing and observing the electron breaks the connection. No FTL information. Its actually comical how far entangled pairs go to generally troll anyone trying to do FTL communication with them.
Physicist here, well done engineer. However, again, there is no "flow" of time as if it is a river. Einstein postulated that all matter has it's own time clock and that it can, and does, tick at different rates for different velocities.
I landed at the same "strict rules" conclusion back in 2007 when designing a sci-fi setting with FTL. I borrowed a bit from Douglas Adams and ended up with a version similar to one you hinted at. That any attempts to perform an action which would result in a paradox would be met with increasingly unlikely events to prevent it from occurring in the first place. Thus, before sending any FTL comms, or engaging in certain kinds of travel, you have to draw the light cones and think through the implications as shown in your video. Thanks for putting this together. It was nice to see someone think through the same things and tie it into a neat package.
I am doing a copy and paste from a quick thought I had. "Just spitballing here, because I am not a physicist nor time traveler, but perhaps it needs to be viewed in other dimensions rather than with a 2d graph. Say for example someone makes a device that in theory can send an FTL message. They turn it on and send a message, but nothing happens so they think it didn't work. However thinking in the infinite universes model the senders universe continued on it's time line, but the message was received in a multitude of parallel universes. They have zero clue as to where the message came from, but they received it none the less. Or perhaps the universes have a way of keeping things tidy, so too speak. So when the FTL message is sent, how do I say this, the entire universe is sent and is no longer where it was in time. Thinking in terms of infinite universes perhaps there are as many, call them anti universes (empty spaces) in the big empty. So the universe itself where the FTL message originated instantly fills the space where the message is received thus avoiding some weird entanglement of timelines. Sure there might be some side effects such as the Mandela effect, but that is price we pay in order to have FTL."
This is what I was thinking. I'm glad to see somebody else thought the same. I even hypothesized that that causing a paradox, that section of time is broken off and takes that space with it, like ALL of that universe at that exact time, essentially causing what would be parallel universe. Sting Theory mathematically checked out, and postulates that a multiverse exists, along with at least 11 dimensions. I think something like this videos scenario paradox happened in the Mark Wahlberg Planet of the Apes. I remember there being a video transmission they received in the beginning of the movie that was actually sent years later...
I think the problem is simply with the FTL going backwards in time in the graph, the thing is the FTL message would be traveling inside space itself, what we could call a fourth dimension where time is absolute, why would it be bound by general relativity, if it's breaking it in the first place?. Then on your graph you can trace it without the time dilation of the ship, thus it would be relative to the earth again and not the ship, so for the ship, their 'FTL' is actually slower than light but for the earth it's traveling faster than light It's the only way to have possible FTL without creating time paradoxes
"The cosmic speed limit, the speed of light is so diminutive compared to a galaxy. It almost seems like a cruel cosmic joke that the universe be arranged in such a way that we are able to look out and glimpse its wonders and yet are trapped here by the speed of light. Fated to only ever peer through the bars of our cosmic prison and dream." -- This is so beautifully spoken...
But isn't true. You don't need FTL to visit the Galaxy, as long as your speed is very close to the speed of light, your proper time slows down a lot. For example, at 299,792,456 m/sec (just 2m/sec less than c) you can reach a destination 720 Light years away in just one month at your clock. But for the rest of mankind, so your family, relatives and friends you are disappeared forever and no communication is possible. This is the real problem.
@@buiosoyeah that’s why it’s basically useless. The few people on board the ship or w/e is traveling would get to experience it, but upon returning the civilization probably wouldn’t even exist
I'm sorry but I.dont see a paradox here for the ftl ship. There's so much trickery and perspective here. Imagine you are on the other side of earth and you discover the country you're in has learned of an atomic bomb strike coming at them, then you see the atomic.bomb on its way, it doesn't mean the warning came first. It's just the order of information you received that's changed, not the ORDER of ACTUAL events. Why do physicists put MORE emphasis and make EM WAVES the MOST fundamental aspect of the universe but not the ACTUAL mass and energy aka atoms which emit them in the first place? Think of em waves as Carrier waves. They don't matter at all. So what if i travel faster than light and I arrive at another planet, stop, and then someone using a telescope sees the light from my body arriving later starting from near the end (where light is closest) and appearing to go back. We would know the light is just an illusion. The ACTUAL FUNDAMENTAL ATOMIC MATTER AND MASS MATTERS MORE THAN ITS EM RADIATION IT OUTPUTS. But we instead only focus on the atomic OUTPUT aka em waves and base ENTIRE THEORIES AND PHYSICAL LAWS around THE EM WAVE. Who cares about light? We've seen that atoms can "communicate" at "infinite speed" via the double split experiments. If particles can communicate faster than light they are MORE fundamental than light. Now sure information can only travel faster than light but why focus on information as if it's more fundamental than the MASS energy? Particles can communicate instantly at infinite distance, and while the information is limited at light speed, so what. Light is just em waves with no mass. Could we make life out of em waves? No. So who cares. If we did travel faster than light THEN saw the light of our travel arrive, I'm sure NO ONE would say "wait how come you're here but yet I see you still on the way?". Everyone would know that it's just an illusion. So I don't see any paradox
According to specific in general relativity. if somehow we were able to have no mass if not 99.99% time would not pass at all and travel to another galaxy would actually feel instantaneous
I watched the entire video, and I get the sense you broke the rules of your own diagram. You drew two diagonal lines at the start, indicating the speed of light. You set the premise that any line between the time axis and this diagonal line is something moving slower than light (STL). Any line between the diagonal line and the space axis are faster than light (FTL). You then start speculating about FTL transmitters able to send a message instantaneously, meaning horizontally to the right. I'm with you so far. This is where you break every rule that has been set. You draw a line that goes downward. We've not established any reason why a line would do that. Your made up transmitter can only go up to a limit of a horizontal line (instantaneous messaging). These paradoxes start popping up because you've suddenly decided this message is being sent to the past. The FTL transmitter is now a time machine for no reason. Like I said there might be some physics I don't understand. However in the diagram you've been using, there has been zero explanation of why any line would ever go down. The established rules were that lines could only be in the STL or FTL directions. Once you start going downward you break your own rule set.
Indeed, why is the first message drawn according to earth's POV but the second one is drawn according to the ship's POV? There's no explanation for that
@@digammaf7060it's sent from the ships pov because that's where that particular message was coming from. However the original comment is correct that it doesn't make sense on this graph as if you map out time/ space for the the ships pov the line going downward would indicate that the message is sent faster than instantly from the ship back to earth. However if you send the message ftl but not faster than instantly than I don't think any causality is broken
@@tb3099 Take 3 points, the first one being the emission of signal, the second one being the relay of the signal on the ship, and the last one being the reception of the signal on earth. Place those three points in a similar configuration as in the video. From earth's POV there is a downward worldline, but if you apply the Lorentz' transform on all three points to obtain the ship's POV there is no downward worldline anymore. In fact, the downward worldline becomes an horizontal worldline, relevant with the idea that the message is transmitted instantaneously from the ship's POV. I just checked that using a graphing calculator, the original comment is not correct about that, and you are not correct about that either. I would gladly share the Geogebra file but I don't know how.
@@digammaf7060 interesting I was trying to figure out how to do it but I don't have a graphing calculator or know what app to use on my phone. On your graph is there a point at which the ships the ships transmitter can send something faster than light but not break causality.
I will explain it to you so you can reproduce it exactly. It's not complicated. The Earth's worldline is the line defined by x = 0 (vertical line perpendicular with the x axis). The Ship's worldline is the line defined by y = 1.18x (arbitrary speed close to the speed of the light). The light's worldline is the line defined by y = x (45deg line). The Signal emission Ma is located at (0; 4), the Signal relay Mb is located at (3.38; 4), the Signal reception Mc is located at (0; 1.14). Now you have the world from Earth's POV. To get the Ship's POV, we will apply the Lorentz transform on Ma, Mb and Mc. First, the speed of the referential we are using is 1/1.18 (we are using the natural units in which c = 1). According to the wikipedia page of the Lorentz transform, we should first compute a factor called Gamma which in our case is about 1.884 (remember to take c = 1 and v = 1/1.18). Then, for each point Ma', Mb' and Mc' which are the equivalent of Ma, Mb and Mc from the Ship's POV, we can compute the coordinates like this: Mx' = Gamma * (Mx - v*My) My' = Gamma * (My - (v*Mx)) (I simplified the equations seen on the wikipedia page because c = 1) We are left with: Emission' = (-6.39; 7.54) Relay' = (0, 2.14) Reception' = (-1.82, 2.15) As you can see, Relay' to Reception' is not a downward worldline from the Ship's POV, the only downward worldline is Emission' to Relay', which is a direct consequence of breaking the speed of light and not relevant. This is not worth discussing because the real issue is not the shape of the worldline: that wouldn't be a problem for causality if both message worldlines were drawn from the same perspective, and that's why I'm telling you that you are not on the right path. The real issue here is that EVERYTHING on the diagram is drawn from Earth's POV, everything BUT that one message reply which is drawn from the Ship's POV, which doesn't make any sense at all. When you are drawing a spacetime diagram, you draw everything from the same POV. Imaging drawing the inside of a house, but for some reason that one couch is drawn as seen from the outside. This is non sensical. When drawn correctly, the diagram is Emission = (0; 4) Relay = (3.38; 4) Reception = (0; 4) As you can see, Emission-Relay and Relay-Reception are the same line segment, which is relevant with the idea that the communication is instantaneous. When switching to the Ship's POV, both Emission-Relay and Relay-Reception are downward worldlines (since we broke the rule of the light speed then it's not surprising to see other funky things happen) but both are the same line segment, breaking no causality at all.
Whoever knows probability applied on quantum multiverse would notice one thing - future timelines are not unique, only past timeline is unique. That also means travelling into future (as we all do all the time) is unique but travelling into past is not. Meaning, if you travel back in time there is probability 0 that you would meet yourself, in fact there is a probability 0 you would meet anything you know. Because at that point in time you would (probability 1) be in a different universe that is already separated from your past timeline. You would have no control in which universe your travel would end and therefore the probability of any paradox is 0. Travelling back in time is crossing multiverse. Bigger concern is what space we would travel through, this is not just an engineering problem since we do not understand anything about the nature of space.
I think as soon as something like FTL is achieved, we'll soon learn that there is some other, infinitely stranger arbitrary limitation way beyond our grasp that we could never have even conceived of before. I have dreams about it all the time, since I was a child in fact.
Same! I think it's just a question of science. As much as i believe in science, we make a lot of hypothesis and assumptions, we are also able to calculate stuff precisely(think gravity) without actually understanding how it works exactly or at the quantum scale. We can measure stuff and make accurately predictions on things because they follow rules, even if we don't understand them at their core. With our understanding advancing we will eventually find out that there's much more hidden stuff in the universe, much more detail to the laws of physics as we know them. I'm pretty sure with time everything we deem impossible will eventually unravel itself with technology. Think about our understanding of gravity or molecules or whatever has evolved, from thinking that something doesn't allow you to leave the ground, to thinking there might be a force, to formulating an explanation to that force, to finding actual data on it and doing research. We will eventually end up finding that gravity is an illusion and happens for other reasons than we think 🤣
@@griseld As much as I like your enthusiasm, and would love for FTL and other fancy tech to happen, wanting it to happen won't make it so. The reason science is so scientific is because of intrinsic scientific value; skepticism. Being skeptical is probably a key to being a scientist. So it isn't really healthy as a scientist to start thinking that everything you know now is completely wrong because something else that people thought was right turned out to be wrong. That kind of thinking can lead you to certain biases that can have a lot of effect on your research. Of course, pretty much all scientists and people want FTL to be possible and would love for it to be so, but also most of them know that as it stands right now, FTL is likely impossible, and, assuming they aren't researching something that could change that, they are probably working according to that. Scientific/technological progress could hit a wall tomorrow, and any advancement could freeze. Of course, that's unlikely to happen, but it is possible. It's good to be optimistic, and enthusiastic, but knowing where the potential limits are is good. I would love for FTL to be possible as I already said, but as far as we know it's either impossible or requires incredibly advanced technology that we won't have for hundreds, or maybe even thousands of years. And our current best theories suggest it's the former, but who knows? Maybe someone will create a theory of quantum gravity that will be proven, and that will allow for FTL.
15:18 If we are looking at things from the ship's crews' perspective, how can you say that the first thing the crew perceives is Vega receiving the message from Earth? How did that information get from Vega to the ship? Was it instantaneous? Doesn't this information take time to travel to the ship from Vega? Yes, the time line has reached Vega, but it hasn't reached the ship yet. In fact, it appears that the ship learns about the message from Earth to Vega when the ship arrives at Vega (this might be an artifact of the speed of the ship, and might not be true for a different speed). More importantly, according to your timeline, the STL ship thinks Vega has received the message from Earth BEFORE THE SHIP HAS LAUNCHED. 18:11 Justify the world line for the return message from the ship. No matter how I look at it, the message from the ship back to Earth arrives later, not earlier. I don't see any way to get your reply world line from any of the other lines you've drawn.
I was feeling stupid for not understanding that part of the video, but my reasoning is the same as yours. I went back and forth in the video trying to understand why the STL ship would see that vega was warned before earth even sent the message. wouldn't that require that ship to see faster than light? on the other hand, I find it far more likely that I just don't understand the use case and I'm missing something that smarter people than me have thought of xD
@@jackie.p6891 The time slice isn't about seeing events it's about them "happening" on that world line. The video is missing some crucial explanation of the STL ship and how it travels. The close to speed of light you are travelling (without FTL) time for you actually slows down and your observations of the world outside are also slowed down. Which seems paradoxical but it's what relativity tells us. So when we talk about what the ship experiences it's really just a question of it's perspective of the outside world. A transformation into the perspective of the ship would produce a diagram where the events happening on Eartth are slowed down.
@@salbrismind The STL ship's space line should be an S shaped curve to account for acceleration to relativistic speeds and deceleration. That would change it's position on the overall chart.
If time is a constant in the equation, then no amount of space warping, special relativity, can make anything go back in time, or can make something happen before it starts. It can slow down subjective perception or slow down objective perception, but time proceeding forward, cannot go backward.
That also includes the possibility of meeting them :( The world could be littered with civilizations, just they might be far apart, or some might even be next to each other, and we’d never know.
If hostile aliens became aware of us through telescopes much more advanced than ours and wished, for instance, to take over this wonderful piece of "real estate", they could possibly, with their advanced technology, attack us with a virus. The virus is so small that it could be accelerated to near the speed of light without breaking any rules. Said virus could be designed to make us really smart, smart enough to change our ecosystem in their favor, and so aggressive as to cause our own downfall through constant conflict. They could then send their STL vessels with colonizers to eventually clean up the mess and take over the place. Its not really far-fetched, in my opinion!
Nothing bothers me more than knowing I will some day pass away not knowing whats out there, I'm gonna die in ignorance and there's nothing I can do about it.
He's an interesting man, I'm the same way. I can get deep into my own thoughts while listening to a video but like you, listened to it in its fullness.
If you moved instantaneously from earth to vega, and then told someone - to instantaneously go to earth, and tell them to shut off the instantaneous transporter, they'd arrive essentially the moment you left. That's significantly faster than light speed and there's no causal issue. The whole reason the space line is the time line reflected by the null line is Because we assume the fastest speed is the speed of light, that's an emergent property of the assumption, and any relativistic effects assumed to also be reflected are affected by that original assumption. If you bend or break space itself to accomplish moving subluminally from point A to point B in a shorter time than light could travel that's fine - if difficult, but it wouldn't allow for paradoxes to arise, you're moving slower than light in your own reference frame, from the reference frame of your starting and ending locations - it's as if they are closer not as if you are faster. If you traveled through space more traditionally as you got close to the speed of light your physical and nuclear properties slow until you reach light speed and they halt, you couldn't perceive a message arriving at your location at this speed and even if you kept a record it wouldn't be reacted to until you reached your destination, upon which even sending the message back at the same absurd speed wouldn't arrive back to earth before it was sent. There's also the issue of spreading out if you behave like a wave at that speed, becoming red shifted as space expands with you moving through it, and if fermions and bosons behave the same way through space at those speeds - you might arrive out of sync in a catastrophic way, unless your beginning and ending points are specific distances away - regardless of how long it took you'd eventually find such a place, and even then they'd need some marvel of engineering to slow you down or put you back together once you arrived. Your mechanical interactions would stop entirely as two objects moving in the same direction at the same speed never collide, no nuclear interaction beyond perhaps making you more or less energetic in difficult to predict ways, the magnetic components would just cycle as you travel hopefully arriving in the right orientation and not becoming a tangled mess. If Everything lined up Just right, you'd arrive after experiencing no time pass yourself, it feels instantaneous to the traveler, and that's only moving At the speed of light. If you moved somehow faster - which is as absurd as constructing a machine Out of photons to propel photons faster - you can't experience less than nothing happening.
Thank you. The whole time on the video I couldn't click to the concept of the video. Sure your warning could arrive before the perception of the event, but bot before the actual happening of the event.
Yet again you combine scientific explanation with a thoughtful and beautiful message. Thanks for one day deciding to start doing these videos, they mean a lot to me.
Why not also mix it with spiritual & religious thoughts?! ⚡️⚡️⚡️In multi-dimensions existence, causality wouldn’t be violated. Abrahamic secret texts of Jews, Christians & Muslims have hinted that “instantaneous” travel is indeed possible if we live within multiple dimensions. Each dimension has its own speed limit. When u reach certain speed, u jump into a deferent dimension & u loose direct connection to ur initial one until u slow down to within its speed limit. 🤔
I'm probably just not understanding this properly, but: Shouldn't the reply from the STL ship _always_ travel *up* every possible Worldline, no matter how quickly it gets back to Earth? Drawing the reply the way you're drawing it, means that _all_ replies back to Earth (even STL ones) will break causality, because you're sending them backwards through time rather than forwards. While Earth, the ship and Vega are all moving through time at different rates, time is still passing for all three; In your example, you're drawing the reply line back to Earth as though Earth were stationary in time from the moment it sent it's message.
It seems to be that he's trying to apply relativistic rules to something that isn't actually travelling through space. I mean yeah if something could travel through space faster than the speed of light then it would go back in time, but that's not what we're talking about. A limitation of the diagram I think. Obviously the FTL message would not be going back in time.
True, this video is circular logic. It used a diagram system that assumes within its design that light is the absolute limit. IF that is true, then this diagramming system is valid. But if we discovered FTL, then this diagram system would thereafter only be about how a 'light and picture show' worked - not actual causality. We would need to return to some other system of determining events which is more akin to a classical system.
I believe you are correct. As I stated elsewhere, I think there is a logical error in shifting frames of reference. Every "slicing" line of the diagram should be at the angle of the speed of light, not at the angle of the ships' trajectory. If you use the ships trajectory, then all other items in the system would also need to be rearranged as the trajectory is now the frame of reference.
@silience4095 The math itself is just a tool and can be correct for the frame of reference. If the frame of refenece is wrong, however, the math will lead to the wrong conclusion. This is what i posit here, not that the math itself is wrong, but rather our initial assumption may be. So i propose that our use of the tool may be incorrect, not the tool itself, if we can indulge in a metaphor. I hope this makes better sense, and I apologize that I was typing my way through my thoughts, as it were.
I'm no expert, but, it seems that the ultimate paradox of sending the messages back in time before the event happened only appears if you switch between the two frames of reference. Which you do (we are talking about material around 19 min of video). To explain, you mark the signal of supernova travelling from earth to the stl ship instantaneously as observed from the earth and then mark how the signal to switch the FTL transmitter travels from the stl ship to earth as observed by the stl ship. If you were to draw the signal lines corresponding to single observer only, they will almost overlap and be parallel. Given a slight time delay in the machine that receives and interprets the signal and sends the signal back (a computer constrained by the speed of light for example) the signal to switch off will be always slightly later. Causality violation will never occur from a point of view of a single observer and no-one would ever be able to experience it, including the machine that sends out the supernova signal and receives the switch off signal, unless they can be in two places at the same time and be able to switch between the two frames of reference freely.
This is exactly what I 100% believe. The line at 18:12 drawn down-left is impossible even if you send message at 1 million x speed of c. The lowest it can go is horizontal (right to left). Thanks for sharing!
Yeah this confused me as the message back from the ship from earths perspective should be traveling upward and left instead of downward and left. In which case no paradox happens. Earth will always send the message before the ship sends the reply.
It's because this is all wrong and your velocity has nothing to do with altering space time. Relativity proves this but everyone likes to misinterpret Einsteins findings. The epxlanation with the clock moving slower the faster you go to lightspeed was not an example of altering time. It was just an example of how the light behind you would react if you approached light speed.
@@naveedrehman6083the horizontal line is earth's reference frame, not the universal one (there isn't a universal one). That line is possible given the space line and the null line of the STL ship.
What is most beautiful about this video - is actually what it has done to the comments section. Look at all the wonder, the questions, the curiosity, the debate. All these wonderful human beings trying to discover - this is what I love most about humanity, we're all in this thing together :)
What if the solution is a combination of two rules? 1. Anything that is going FTL cannot physically interact with anything going STL. 2. When exiting FTL, your world line is also precisely what it was before you engaged FTL. For example, an FTL ship cannot instantly travel to an STL ship, and exit out of FTL with zero relative velocity to the STL ship. This would make the STL ship intercepting an FTL message impossible. The only way to send messages FTL is by way of literally sending a physical ship that exits out of FTL at the destination. A message that simply travels through space and can be arbitrarily intercepted by any observer is just not possible. The FTL ship could also fly out to the STL ship at FTL, but in order for it to ever get back to Earth earlier than it left, it would have to accelerate to have a zero relative velocity to the STL ship from this example. But then that acceleration would take time, preventing it from getting to Earth before it left. I dunno, I’m no physicist, so I feel like I have to be missing something here, because that type of restriction doesn’t feel too arbitrary to me. This could just be me not yet picturing some other diagram following those two rules that still break causality. Seems like the isolation within FTL, and your relative velocity from your departure being conserved in the jump, both feel like they might be more of like natural consequences of how an FTL drive might actually work.
I agree with you and just said something similar in response to another. I think we collectively miss the fact that radio messages are transmitted absurdly slower than any speeds we are trying to achieve physically. So we wouldn’t “know” what happened to a vessel on the other side of successfully achieving FTL speeds unless that vessel signaled back. And how long would that take? “God only knows” as they say. That’s assuming we couldn’t return the vessel home with its findings. All wild thoughts. But science and logic tells us it’s possible. Still solving the “how”
Was just thinking about this concept of world line alterations as I was (re)watching this video. The notion of intercepting an STL message while in FTL somehow confused me/didn't seem like it should be possible in that reference point.
The last part at around 18 minutes isn't really explained well. Why is the line going back in time? I spent like 20 minutes staring at graph lines to figure it out. Basically if you extend the STL axes into the negative direction, you can draw their bounding box for 'time-positive travel' aka non time-travel, which is any point 'above' the STL space line. But because the STL axes are so skewed, there's a very unintuitively large amount of area on the earth-centered graph that represents positive time / negative space movement for the STL ship. So a ship travelling FTL from the STL frame of reference could very well travel "back in time" from an earth reference frame. A similar application of this logic is that the space axis of the STL ship is actually an FTL line in the earth frame of reference. So an FTL traveller in earth's frame would appear to be instantaneously travelling to any point in space for the STL ship. In that case, the FTL ship would exist at every point of it's travel in that moment of time for the STL observer, which is another paradox, or it would discontinuously travel from start to end in zero time. So in theory, a wormhole could actually be FTL travel in another reference frame. When you start with this example, it then become clear why travelling faster than 'wormhole speed' results in moving backwards in time. To one frame of reference, it is a "valid" FTL velocity going forward in time, but to another frame it is moving back in time, since that's the only thing faster than moving through the 2nd frame in zero time.
Noticed the same thing, message goes back in time instead of forward in time but faster then a regular light speed message would. in instant message would be flat. this is someone between a light speed and instant but suddenly goes the wrong direction on the axis.
Let's start perhaps with a more modest goal: Alcubierre-style drive that targets STL flight instead of FTL. Even that would be a tremendous step forward for our civilization.
That seems like it would be more difficult than actually achieving FTL. I would think that simply creating the warp bubble is going to be hard enough, and generating the energy levels and creating the exotic matter required is a monumental achievement in and of itself.
I disagree. What we should actually focus on is achieving relativistic STL flight directly. By my understanding, the closer the ship gets to c, the less time they experience throughout their trip (as the length between their origin and destination contracts, or as time dilation, depending on reference frame). Assuming STL travel close enough to c, one could get to almost any location within the cosmic event horizon, while only experiencing the amount of time it takes the ship to speed up and slow down from its own perspective. The only problem this results in is that all those who aren't also travelling relativistically will be left in the past by the crew of this ship by a number of years equal to the number of light years travelled (this is the effect that would be solved by FTL travel, for what it's worth). It seems to me that an STL Alcubierre drive would remove the length contraction / time dilation effects from the crew, since they aren't actually moving, which would paradoxically possibly make the trip longer for them than if they had travelled traditionally at the same rate as their warp bubble travelled.
@@rarebeeph1783 I don't think that relativistic speeds are going to be possible for humans due to the often overlooked relativistic effect of mass dilation, not time dilation. The faster you go, the heavier you become, and there's no telling what that is going to do to the ship itself, much less its crew.
But the possible negative effects of relativistic travel might only be dealt with by warping space itself rather than accelerating to higher and higher speeds. That makes warping the most likely of ways forward, or at least the least problematic. But then there's the question of what that's going to do to the universe itself when such a warp bubble is created. Seems to me it would result in a singularity or something even worse. ;)
Edit: Cleaned it up. As others have mentioned, the only constraint necessary for a vector to have a >= T (Time) value. The problem is that T and S axis are different for different frames of reference. The one frame can have a vector with positive T (maintaining a dot product == C), but be a negative T vector (or dot product C) when translated to a different frame of reference. I think then the problem, all vectors having a positive T (and vector dot product == C), would be solved if there was an absolute frame of reference. A possibility frame would be the expansion of the universe. If all vectors are then constrained to having a positive T (and dot product of C) on the universal frame, regardless if a vector from one frame translates into a negative T vector in another. The universal constraints would then not be violated. That also means that "time travel" would really only be within a local frame, not the universal frame. Local paradoxes resolve on the Universal Frame. I think that makes sense. And hopefully I used the correct terms; my math is old and shaky. IANAP (I am not a physicist)
A universal frame by it's nature would disproof relativity, however. But many scifi shows do use it as as explanation for why FTL is possible but doesn't break causality (hyperspace, subspace, etc). There's an adage in scifi circles, "Relativity, Causality, FTL, pick any two".
Hyperspace does not break causality, it just abolishes relativity. Even Hawking once admitted that in sci fi interstellar travel can be made fast if the author so wishes, as FTL travel would allow an astronaut to travel many times in his career instead of max. 1 expedition. And even if that cancels relativity, so be it. By the way, even Herbert Wells' Time Machine does not break causality. A 19th century man goes to the future, sees it and comes back to tell the story, no causality broken. Some sci fi authors do break causality to create intellectual puzzles (Harry Harrison's Time Machine Saga or William Tenn's Discovery of Morniel Mathaway) but that is a different theme altogether.
FTL does not break causality, at least in sci fi. In fact, hardly any sci fi writer breaks causality, except for a couple of authors breaking causality as intellectual puzzle (Harry Harrison's Time Machine Saga or William Tenn's Discovery of Morniel Mathaway - by the way, none of them has anything to do with space travel). FTL just abolishes relativity. Edmond Hamilton, Isaaac Asimov, you name it.
From the messages point of view, even if it was travelling instantly it still has to travel "through" all the light emitted from the destination. If its destination is 1 light year away, while travelling towards it it will see the destination experiencing a full year. If it then turns around and looks at the source it will be a year in the past from when it left but if it immediately heads back it will not arrive a year in the past it will see the source experiencing a year in an instant and arrive at or after the time it originally left.
Well, you're describing what would happen to a message travelling at the speed of light. The whole point of the video is to look what would happen IF the message was travelling FTL, or intantaneously in the part you're refering to... Imagine a message that would be sent right into a wormhole and directly to the ship. It wouldn't have to travel "through" anything.
@@norbertlauret8119 no, I was describing instantaneous travel. If the message was moving at the speed of light it would have taken a year to get to the destination. During that year it would see the destination experience 2 years worth of time, I.e its time moving at double speed, and then it arrived and turned around and looked at its source it would see it still at the same time when it left. If a wormhole goes to the past then it breaks causality naturally but that's a completely different thing and makes the graphs in the video irrelevant anyway.
I’m in favor of the conclusion that if we encounter “paradoxes” in a scientific thought process we should consider that the concept is flawed. However, I would point out that the chart has problems when using the STL craft and it’s time slice. Even if one buys that the STL time slice is the correct angle here, it still matters where the craft is on that slice. The crew doesn’t get to instantly “know” when Vega sees things. You’d have to allow time for Vega to send the signal to the craft and by then the light from the super nova might have already reached the ship. In addition, the ship’s movement through space over the course of the events it does perceive would affect the value of this visual.
Don’t think it matters that the STL crew doesn’t know about the vega point knowing. The point of view we have is omniscient seeing how all three points interact, not just the STL craft. The problem the example is showing is if FTL Messages gets to a point prior to sending it.
Just because they didn't see something happening doesn't mean it didn't happen. They can easily calculate the time of all the incidents. Let us say that Vega sent an FTL signal to the ship after receiving the FTL signal from Earth. On receiving the signal, the crew(of the ship) can calculate the time of origin of the Vega signal. Then they could also calculate the time of origin of the Earth signal. Using that information they can find the time of the supernova. Now, they have the whole timeline which they can use to see the discrepancies. Also that is not the only causality being broken. Pause the video and then look at 14:55. You can see that if the crew intercepted the warning signal, they themselves would see the warning even before the supernova happened and even before earth sent it.
@@devverma144 in regards to 14:55...the STL time slice intercepts the signal...but what are the changes that the ship/crew are at that moment in their time slice.
@@davidmccoy1378 Why would we talk about instances where nothing happens? Let me try to explain: We are talking about a hypothetical concept(faster than light travel). If that hypothetical concept is possible then it would never break causality. So we are deliberately trying to look at those (possible)scenarios that would violate causality to disapprove the concept. Here is an example that has nothing to do with causality but maybe it will make things clearer: If you are trying to disapprove a business that states that their armour is indestructible, you would try out scenarios where the armour is subjected to gun shots or other weapons and not the scenarios that involve the showering the armour with rose petals.
My mind is blown. When you switch the communications to "instantaneous" and re-explained the diagram, everything started making sense. I have had so much trouble trying to conceptually understand these potential issues with FTL travel/communication and this has helped so much. Still hope we figure out a way around it, though! Like you said, it's criminal to be able to see all this cool stuff out there and not actually be able to go see it ourselves.
This video misleads - as it shows jumps from future to past like its space and not time. Once you reach any point in that diagram - you can only move up (or sideways if instantaneous) but never down, same with sending messages.
I also agree, although after a few times of piecing it together, I think this is what I came to. Under relativity, the speed of light is constant, therefore is that 45º line between the vertical of time and horizontal of space. Any observer is always going to have their own time line vertical and their own space line horizontal and the null line or speed of light line halfway between them at a 45º angle. So as someone else speeds up on your graph, their line will tip towards the right. This is their time line but their space line is also tipping up, both getting closer and closer to the null or speed of light line. I think it gets easier to comprehend once he switches over to instantaneous messages because those are parallel to the space line. So its easy to see why a line leaving the STL ship leaves parallel to what its space line is. I think the part that I don't understand is why one instantaneous or FTL message gets placed parallel to the earth's space line and yet the return message from the STL ship is parallel to its own space line. So I get the math of why the line is that angle, but I don't understand why 2 instantaneous messages don't have lines that are themselves parallel.
Indeed. Given the diagram, isn't their reply being sent backwards? Surely their message to earth would be in a diagonal going up and left. This is because time is going forward so the path of any action should always point upwards except the instantaneous lines which are flat ? (In an angle that mirrors the light speed line).
@@danielebowman this is exactly what I’m having trouble with. Their time line is going upward, so sending or receiving should be higher from where they started. I wish I understood this better, but the paradox didn’t make sense on that graph, or could have been drawn better. I don’t know why it’s angled down.
@@MagicScorpio I think it's easiest to see it when you actually tip the graph to the angle of the STL ship's space angle. The time access for the ship was shown moving up and to the left through the graph. The STL ship using FTL communication back to Earth sends on it's space angle, which intersects with Earth in the past.
Humans once looked to the sky and wanted to fly above the clouds. I'm sure that seemed just as unattainable as ftl. Granted it is orders of magnitude more difficult to achieve, but I hope it's something we never give up on. Venturing a guest I'd say we're not looking at reality the correct way for ftl. It will take a totally unexpected discover that requires us to create a new model of physics and just reality in general before we can do any real work on the issue.
I think it didn’t seem impossible as we always saw birds flying. We just imitated them. But ftl has no inspiration. Maybe if we meet aliens. Or maybe if we do use ftl, we might go to a parallel world which doesn’t result in a paradox.
@@Primarycolours- I'm pretty sure it's not galaxies / objects that are travelling faster than light. It's space that is expanding at an increasing rate. That is one of the concepts addressed in this video, about time and space. The objects in space are still moving, but not faster than light. It's space that is expanding which we then perceive as accelerated motion. And since nothing can move FTL that's why we perceive a red shift as space is expanding... I think.
@@RuchiinChina in space times doesn't works very well, and faster than light is possible but not with our current understanding. We needs to find negative energy materials which can't be here on earth.
I like how he predicted every point where I got confused or skeptical and delivered a good answer without me ever asking anything lol About the talk in the end about exploration without FTL, it was quite poetic, but individuals can actually experience it one day and travel to many stars, considering there is no barrier in the laws of physics that say living things can't last for billions of years. More than that, the way in which time is perceived can be drastically modified, where a million years travel can feel like a mere hour. Just imagining human-like consciousness in a digital substrate is enough to see how this things are possible
Even if we stay our squishy selves, we can cross our galaxy in under 25 years (traveler's time, because of time dilation) going at a comfortable 1g halfway and decelerating at the same rate the other half. Even going to the edge of the universe will take under 50 years in these conditions. Maintaining that acceleration that long will require insane amounts of fuel of course (i.e. the annihilation of 600 million tons of matter and antimatter as fuel for crossing the galaxy for a 100kg payload), but it's nice to think it's "possible" in some ways.
Looking at my cat, I cannot really fathom what she is truly thinking as she stares back at me. With this in mind, I truly have no way to imagine what a "human-like consciousness in a digital substrate" would ever feel like. I suppose it would be as alien as comparing my consciousness to that of an ant...
The key problem ;; we can't even police the Internet today ; how could we possibly prevent the misuse of time travel tomorrow - we all know , how corrupt some people are..?
I would posit that it is possible it's just all about frames of reference. You would not be able to affect anything in your personal referential past. You could observe it, but not change it. I think the diagram is off in using the frame of reference for the STL ship as the "speed" of their FTL message would be significantly "faster" than the message from Earth. The correction for this means that their message would NOT arrive prior to that of the sent message. (On the graph their message would appear to them (could they see the graph) to curve upward past the message point. Using star trek terms if you fired off a message at warp 1 its not going to travel at (warp 1 + full impulse) simply because you were going at full impulse. Basically this graph "forgets" that for all of the pink FTL lines, the straight "space" line is not straight. For them it is a curve, so if you factor that in and the flatten it back out it shouldn't violate causality. I am probably wrong somewhere, it's 2 in the morning...
Saying that "the line is not straight" and implying it should be straight is basically equivalent to saying "relativity is incorrect." Now, you can have FTL travel AND causality if you scrap relativity, but unfortunately, relativity looks highly likely to be true based on our current assumptions. And relativity means those strange angled paths through spacetime, where by going really fast in a frame of reference time will pass differently (seems to be experimentally true for satellites with clocks in orbit!). (And yes, I know that the video seems to claim that relativity isn't the problem, but... it totally is, I disagree with the video on that.)
@Peter Ingraham no, what I am implying is that this graph is uses a straight line (thus treating it linearly) vis a vis space whereas the whole concept discussed involves bending or folding space. I do not think relativity presents a problem as I have discussed as I believe it sorts itself put if you discount momentum and the standard rules that apply to speed and motion as you would have to when folding space itself. Similarly to how the rules change when you approach a black hole they would change when you folded space. As such, this graph assumes that if they are traveling at (using star trek references just for ease of discussion) warp 1 and fire of a beacon at warp 1 it will be traveling at warp 2. It will not. I posit that folded space travel is a definite limiter such that you cannot increase the speed simply by initiating a launch from something going at speed. As such it would APPEAR to curve away from the perspective of the FTL ships view on the graph IN ACCORDANCE WITH RELATIVITY. Whereas it's not actually making a curve on the graph because the graph treats space as linear and FTL travel does not.
It may be right or wrong but the fact that it is showing 4 dimensional space-time on a 2 dimensional graph, it's like trying to show a 3D cube in 1D, it's simply not doable or at least it seems to me. From what I learned we are able to show a cube on a 2d sheet just because we are able to visualize the depth of the image and draw a "line behind the lines" that how we create 3d in short we are able to circumvent one dimension by imagining it so 4d can be shown in 3d, 3D in 2D, 2D in 1D, jumping from 4D to 2D doesn't make much sense and many things may not match like they should. That I think is the main problem here that there is just no way that he could show what he wants on 2D sheet. Rather than FTL I am more convinced by Einstein-Rosen bridges theory beacuse from what I know they go through additional 4th dimension of space there for not creating this paradox if its true. (sorry for mistakes if any english isn't my first language)
Surely the ‘paradox’ stems from the problem that your graphical representation ‘calculated’ the outgoing ‘instantaneous transmission’ from the Earth’s frame-of-reference, but the incoming ‘instantaneous transmission’ from the STL ship’s frame-of-reference. I would have thought that two instantaneous transmissions from A to B and from B to A (both sent at exactly the same time) have to follow the same path through space-time when modelled in a single frame-of-reference. Which would mean that both transmissions lines should either be parallel to the Earth’s time axis or to the STL ship’s time axis, depending upon which observer is measuring the path through space-time.
This makes sense. It’s feels like just that the STL observers may “think” that there message to earth has been received by earth before it was sent. But from earths perspective, in Earths frame of reference, Earth to STL and STL to Earth will be instantaneous. So probably like as earth receives response as soon as it sends!! Which now that I think of it, is actually close to breaking casualty.
@@SagarThorat Breaking causality? Assuming that it were possible to travel at twice the speed of light (2c, and without relativistic effects) to a star that was 100 light years away. You arrive there 50 years after you left Earth. You make an instantaneous transmission back to Earth. That transmission is received 50 years after you left. Causality remains. As the travel time tends to zero, the required multiplier of c tends to infinity. Causality cannot be broken that way…
I'm pretty mixed up here but doesn't the idea of instantaneous transmission inherently violate relativity? The paradox is in trying to reconcile these two concepts.
@@cavemanraveman1 Yes. Trying to explain that nothing can move faster than the speed of light by using a ‘sub-light’ spacecraft and a transmission travelling at ‘c times infinity’ (an instantaneous transmission) is, I believe, where the problem lies (Too many uncontrollable variables). As far as I was aware, none of the ‘Warp-drive’ hypotheses allow a spaceship inside a ‘Warp Bubble’ to send any transmission (information) to the space time outside of the Bubble, and no one outside would be able to transmit in. If the Bubble was collapsed, the spacecraft would then be exactly as it was inside the Bubble and not moving relative to it’s starting point (remember that with all of the current Warp-drive hypotheses it is the Bubble of ‘Space Time’ that is moving, and not the ship). If the ship is not moving relative to the Earth, they are both in the same frame-of-reference and hypothetical instantaneous transmissions would not destroy causality anymore than saying “good morning” to a co-worker standing next to you would. Also: Imagine three galaxies in a straight line, A, M (our Milky Way) and B. A is to the left of M and B is to the right, such that A & B are receding at 0.75c in opposite directions, due to the universe’s expansion of Space-Time. How fast are they receding from each other? Remember, General Relativity puts a speed limit on moving things, but not on the expansion of Space-Time itself. These two galaxies are not actually ‘moving’ with respect to each other (even though they might move relative to their local group by gravitational attraction) - it is Space-Time that is expanding that is causing the increasing separation. Also, as A will never be able to view (and hence know of the existence of) B and vice-versa, there can be no causality problems (people rarely send messages to others that they are unaware of).
I try to do it by hitting the light switch while simultaneously jumping under the ceiling light bulb fitting. after 9 years practice it feels like I'm about there. also I got those 9 years back just because its kind of magnets
I actually just imagined myself as light going around the world in an instant and turns out I succeeded. It felt instantaneous and there were no measurable details of the event, but it was still awesome because it happened.
I have an even cheaper option. Get a mirror, then walk towards it. You are trevelling in the opposite direction the fotons reflected from the mirror, so you are travelling FTL from that light's point of view.
I enjoy that you are actually including the possibility of breaking the universe in this video. That is why we stopped increasing speed, in my warp engine space ship.
The problem with this is that the perceived time, perspective of the relative time, for the STL ship does not change the physical location of the ship. The STLs reception of the message isn't at a time, it is at a location. In the STLs location, there is a perception of time, but that does not change its absolute location. There is no paradox. Additionally, STLs space and time axis are reversed in this diagram, which is from the earth's perspective. Time relative to the STL will pass slower than time relative to the earth as it is moving incredibly fast through space relative to earth. No expert here but it doesn't take a rocket scientist to realize the proposed diagram is incorrect. Even if perspective changes and time passes relatively differently for the STL, the location doesn't. There is always an absolute location for a given object affected by time.
What you're failing to acknowledge is FYL... the message that gets sent back returns horizontally and very frustrated. Fusion crust and burnt moon pies are heavily encoded in this message. At perfect instantaneous FTL messaging actually looses the T and quickly adopts Y instead , which altered all "C"/ Light Speed lines 75degrees. FYL "fuck your life"
That seems correct to me, as their response would originate at the mark but necessarily be traveling \ rather than /... I feel like I just wasted 25 minutes.
Not to mention everything else on the diagram moves bottom to top along the time axis, yet he drew the response from the ship top to bottom? Lmao he broke his own diagram and is apparently too clueless to even notice it.
@@J3loodT4lon I think it's just very poorly explained why the line is drawn like that. I'm not an expert, but what I understand is that as you move very quickly in your space ship, time moves very slowly in relationship to earth. Say every 1 day you experience, 3 days on earth pass: time is essentially out of sync between the two places. Now Earth is in the future and knows about events (like the supernova) which to you have not happened yet. But with information going less than the speed of light, you could never be informed of the supernova by earth before it happens because by the time the information reached you, it would have happened. However, with FTL travel (let's say instant) 3-days-later Earth can now inform you about events which have not yet happened. If you then returned an instant FTP message, the information is now synced to your timeframe where only 1 day has past and the supernova has not occurred, and it would reach an earth where also the super nova has not occurred, informing them of future events. I think this idea is where the wrong looking line is coming from: information is essentially jumping from one timeframe to another. It's going from a place where 3 days have past to a place where 1 day has past.
Have you done the math with the actual Lorentz Transform equations? In the case of instantaneous travel, there are 3 events that occur at different locations and different times according to the two different reference frames. A message is sent from Earth the the STL ship and then back to earth both via FTL. It is absolutely vital in this situation to define the first two controls: The Earth time + location the message was sent, and the STL time + location the message was received. Once these controls are put in place, the diagram as shown no longer works (FTL breaks the rules of this diagram). However, the underlying Lorentz Transform equations are still valid. You will find an observer at a distance can witness events that are out of place, but NO message can be sent by any means before the origin, even with instantaneous travel! I have done the math several times with the correct controls, and Sabine Hossenfelder released a video that agrees with this finding.
If the message to earth was instantaneous, then wouldn’t the space line for that message be horizontal & arrive in earths future This makes me think that the space line of a FTL massage to earth would take longer than an instantaneous message, which makes me believe that the space line would be upwards rather than downwards as shown in the diagram and arrive in the future.
I'm having a lot of difficulty wrapping my head around some things here. For example, why is the space axis a mirror-flip across the null line of the world line? For the "stationary" earth I get that it would look like a mirror-flip, but why is it? Also, when the transmission is sent from the STL ship after receiving the earth transmission, why is the slope negative? I feel like having this side-by-side with a similar diagram for the STL ship's perspective (with its world line being vertical, and the others being angled) would help clear things up... Like, I get that there's some consideration here for time dilatation, but wouldn't that be bypassed too, as using something like the Alcubierre drive, the object is not actually moving FTL, just the space it resides in is, so it wouldn't suffer time dilatation... I'm just getting confused.
This is where I'm stuck as well. I feel like the mirror line is the most critical aspect of the problem, but is also the least explained. He says, "Now, adding the null line back on we can note the relationship that the space axis is really just a flip of the time axis around the null." This statement is just kinda thrown out there like it might as well just be a coincidence rather than a requirement. But he's a smart guy, so I'm sure there is more to it that gets lost in the explanation. Here is what I really don't understand. FTL travel is obviously impossible if what he's saying is true. So then why are people spending years of their lives working on possible FTL ship designs? Is it not a complete waste of time?
Whole this explanation is a little bit wrong, straight lines are from special relativity theory, but relativistic slower than light ship need to have curved lines from general relativity, so space lines of the ship is only local oriented, and not apply to the whole universe, but(to be fair) the general relativity theory allows close temporal lines that breaks causality.
If you want to a deeper explanation, check out Section 3.3 of williamsgj.people.cofc.edu/Minkowski%20Spacetime.pdf. It really comes down to Lorentz transforms. That the FTL ship is isolated during its trip doesn’t really matter, it departs and arrives in regular space time and is able to reach its destination faster than a beam of light (a beam of “causality”) can.
What I love here in the commentary is everyone having the freedom to express their thoughts in either direction or in neither direction. Where I stand, the whole thing is a big mind F - - K. I want “want” to believe we can break the Ftl barrier, but any basis for that desire does not include any scientific knowledge or fact at this point in time. But, it’s fun to talk about. Peace.
The more I learn about it the more pessimistic I get, for example the Alcubierre drive is only a "solution" if it only is ever allowed to move in one direction (to avoid the light cone) and there isn't a second drive going in the opposite direction. For that to be somehow mandated by the universe would violate another fundamental tenet of relativity--that there is no preferred reference frame (i.e. among other things, the laws of physics are not different in one direction than another). People might be fine with giving that up but these kinds of symmetries are very fundamental and form the foundation of science as we know it (and have been tested to death in other regards). IMO, the impossibility of FTL causing time travel makes other stuff make *sense* too. Because what is travel into the past, really? Another way to look at is that it's a way of *changing the entire universe* (because you have to wipe out all evidence of the real past). How much energy would that take? Infinite sounds like a good answer! And how much energy does it take to accelerate matter to the speed of light (or decelerate a tachyon to the speed of light)? Infinite energy! It all just kind of works *and* provides a neat physical explanation for why we don't see time paradoxes. Whereas every attempt to justify FTL immediately runs into a whole host of problems. At some point, you just have to accept that FTL just probably isn't real. And one final thing... not being able to go FTL doesn't mean not being able to explore the stars in your lifetime! Theoretically, you can still get as close as you like to FTL and reach anywhere you want (modulo cosmic inflation) in any finite amount of time *from your own perspective*. You just can't do it and expect things to be the same when you get there. How would that look from your perspective? As you travel faster and faster, it's like the universe shrinks in your direction of travel--everything looks "short" in that direction. By using insane amounts of energy, we can compress the whole universe (or at least the small part of it where we travel) and cheat the cosmic speed limit! The universe gets so small, having to travel below light speed really doesn't seem like that big a deal anymore. Or like someone said, "the universe is a cramped place for a neutrino." To me, that's at least as cool as any proposed FTL mechanism, and it's 100% real.
The greatest explanation so far. I've been trying for months to understand this by reading forums and watching youtube videos. None were able to explain this. I still need to understand it more intuitively instead of through looking at lines, but this definitely opened my eyes. This is by far the best and most simply explained video so far on this. Thank you
Imagine a yellow star 10 light years away If you were to travel at the speed of light, it would take 10 years to get there right? lets say your friend is watching it in a telescope, 24/7 [LIGHT SPEED] - fly to star at light speed (10 years) - turn star purple - fly back home - (10 years later) you and your friend see in the telescope that the star turned purple [FTL] - instantly travel to star - arrive at star 10 years in the past - turn star purple - you might say, well the friend would see it instantly change - think about if instead of instant-travel, you travel with the speed of light back. toearth.. shouldnt it be purple the moment you land since you were traveling with the purple light? - also.. what happened to all the light that was traveling to earth? think about a middle-planet only 5 light years away from. the star instead..what do they see? -- at least how I understand it I think haha, but. who knows maybe there is infinite universes and you just jump to some alt dimension that is 99.9999999% the same except that the star turned purple at one moment instead of the other
Wrong right away. Why do you travel in the past when travelling instantly? Just zero time passes. You arrive there at the same moment you left, not in the past. You turn the star purple, instantly go back and then 10 years later photons reach Earth and you see the star purple.
@@dmitriimalikov6437 this and also why slide the world line parallel to the space axis. It's almost like you have to change the rules for the paradox to take effect.
I'm not buying it. Just because the supernova remnants, Earth, Vega, and the STL ship all experience time flowing at different rates, doesn't mean that instant comms between them somehow causes signals magically to go into the past. It happens at the same real moment, with different perceptions of how long it took to prepare a response. Fundamentally, the perceived paradox comes from using a special kind of graph that seems to have been designed for the purpose of causing confusion. More broadly, if you see a supernova and then zip over there in your Borg transwarp conduit, you will NOT go back in time and see the star before it exploded. That's just silly. You'll find supernova remnants, emitting light that you'll outrun on the way home again. No time travel. Nor does sending back info about the supernova remnants via subspace, and receiving responses about how to collect better data, somehow cause causality violations. If you somehow outrun your last few messages home, oh well. It's like surface-mailing a postcard immediately before boarding a jet to the same destination. Or like lightning traveling faster than thunder.
The direction of the return ftl message from the stl ship is unexplained here. I would love to know the reason for that, seems like the most important part. Wonderful vid, very informative and easy to follow!
It had something to do with the local reference time line being tilted, which also felt unexplained. If the diagram is drawn based on Earth's perspective, or even some sort of objective third perspective, why would the timeline tilt at all?
It's because for the message to be ftl, it has to be under the yellow line, if the message went up, it would go over the yellow line and thus not be ftl
@tbunreall is correct. To elaborate, we’ve measured the speed of light to be the same no matter what your velocity is, i.e., the yellow line stays put for both Earth and the ship. The only way that can happen is by time slowing down as your velocity increases. So from Earth’s perspective, time has slowed down for the ship and vice versa. That is equivalent to saying that if two objects are traveling at different velocities, their time axes will be different. Now to get the space axis, you have to flip the time axis around the yellow line. So their space axes will also be different. An instantaneous message has to be parallel to the space axis of the sender. The instantaneous message from Earth to the ship is parallel to Earth’s space axis while the *_RETURN_* message is parallel to the _ship’s_ space axis. Anything slower that’s still FTL has to have an angle between the yellow line and the space axis of the sender. Please let me know if anything is unclear, it helps me learn too!
This video is incorrect and gives wrong conclusion. Draw a 45 degree from STL towards earth. You can still do FTL lower than 45 degrees but it will be above the moment when original transmission was made. Logic in this video is false
I agree it's the most important part of the video and yet it doesn't seem correct to me either. It really does need an explaination because the whole video depends on it ! xD And no offence but the replies you got don't convince me. Hoping for a better representation ;)
Best explanation of time travel paradoxes I've seen in a long time, thank you for this! I feel so amazed that on one hand we can theorize and explain stuff like this yet a lot of people will still doubt that we ever went to the moon.
I don't think we went to the Moon, too many variables and orbit and where it's going to be and how do we get there if you look at Apollo 13 movie with Tom Hanks they talk about the 8-ball bubble how do you get orientation when you're not on Earth
@@joehopkins6724 dude, there's a decent shout for never breaching LEO. but your argument is instantly null and void when you're bringing up hollywood movies lol.
There are still people who think the earth is flat. Even though the first circumnavigation of the earth was completed 500 years ago. The problem with time travel is if it were conventionally possible we should already have had evidence of time travelers and it would be very easy for anyone from the future to prove it. From a theoretical standpoint, M-theory is the only possible solution to the paradox I can imagine but still seems impossible to prove regardless.
I am a PhD astrophysicist. The main points of your video are incorrect. Alcubierre travel will not create temporal paradoxes. This is because the universe is moved around the ship. The ship stays in an inertial reference frame cordoned off from the remainder of the universe. Time passes the same for both the external universe and the ship. Things are only different within the Alcubierran bubble itself, but that in and of itself does not imply time travel. There is also no worry about a complex gamma in the special relativity equations because the ship is technically not moving at all. The universe is being moved around the ship.
Thanks for watching for a fellow PhD astrophysicist! Alcubierre himself concedes it violates causality and creates paradoxes, see papers linked in the description. (The point about the ship not moving is irrelevant)
@@CoolWorldsLab I believe the problem lies on how we perceive "Time x Space". If we had an "Instantaneous ship or transmitter", wouldn't "Time axis" cease to exist on that machine? Perhaps, "Time axis" collapsed onto "Space axis". It means "Instantaneous ship or transmitter" when it comes to "STL Ship" will take "STL Ship" 's "Time axis"....which is also the "Time axis" on Earth. Nothing is violated here. For "FTL ship/transmitter but slower than instantaneous ship" that comes to "STL ship" from "Earth sees X", it will take a little while to get to "STL ship". Also, I think you FORGOT that "Earth sees X" is also moving through "Time axis" as well and at the same time "FTL ship/transmitter but slower than instantaneous ship" is moving. Meaning at the time "FTL ship/transmitter but slower than instantaneous ship" reached "STL ship", "Earth sees X" and "STL ship" are parallel on the "Time axis". In this case, nothing is violated also. So even if "STL Ship" has a "Instantaneous transmitter" to send a "Message" back to Earth, it doesn't matter cuz the "Time axis" on the "Message" cease to exist. Earth is always parallel with "STL ship" on the "Time axis". "FTL ship" or "Instantaneous ship" 's timeline doesn't matter at all because it never goes under "Space axis".
@@CoolWorldsLabhey, i have a question. i know the vid is a year old, but if you see this, a reply would mean much to me. you said that the „time slice“ (the line that determines the causality) need to be parallel to the space axis. but that way for the stl ship, the time slice doesn‘t follow the direction of the stl ship‘s time. wouldn’t it make more sense to move it perpendicular to the time axis? i‘m sure i‘m wrong, but i don’t get why. also why is the space line flipped and what does it even say? it‘s not like the stl ship exists in a separate dimension, right? are there any materials i could look at?
well in this case there is nothing to attempt, speed of light is fundamental part of spacetime .. going faster follows same logic as lifting chair up while sitting on it
18:44 This paradox will never happen. Thats the point, it will always be a closed loop. Similar to Delayed Choise Quantum Eraser experiment. It is the same thing... I know it is hard to understand, but yeah, FTL is possible, time travel as well and it does not lead to paradoxes ! U can imagine it as those events are linked in time and they always happen (forming a closed loop), no matter what you will do between those events. Also on quantum level in very short times, the causality breaks down... You can apply this to whole universe. And yes, time paradoxes are not possible :-) as Steven Hawking said. Also, what do you think about the UAPs ? I would say they use FTL travel without a problem and some nonsence about causality does not bother them :D.
This video made me think of a really enjoyable sci-fi novel I once read, called "The Depths of Time". In it, humanity has the ability to use artificial wormholes to traverse the galaxy. These wormholes *also* traverse time. Since they only have STL ships, they travel at sublight speeds (with the entire crew/passengers in stasis) for upwards of say, 100 years to the 'up' end of a wormhole, traverse through it which takes them a great distance and 200 years into the past, then travel at sublight for another 100 years (plus maybe a couple weeks) to their destination. Thus, arriving thousands of light years away only two weeks after they left. To enforce against time paradoxes, there is a highly armed and technological 'guard dog' type of group that protects these wormholes, and ships that use them have their communication systems highly encrypted/deactivated so they cannot communicate with the outside universe while they are in 'their own past'. It's also interesting engineering, as although the ships may have chronologically only been in service for a few decades, they may have tens of thousands of years of travel on their internal chronometer...
@@master_wayki May I ask what trilogy? Is the one I mentioned part of a trilogy? If so, I didn't know this and need to add a couple more to my kindle library!
@@falsfire just saw that you replied. Yes! "The Depths of Time" is part of a trilogy. The other two are "The Ocean of Years" and "The Shores of Tomorrow" in the "Chronicles of Solace" trilogy. I ended up having to buy those two because no library for hundreds of miles had a copy of either. Very, very top-notch books! They drew me in like no other books had done for years.
Sir, I only found out about you less than a month ago but have almost instantly became obsessed with your content. Keep it up man, I love everything you put out.
I always love the very grounding and philosophical thoughts proposed in these videos along with the theory. Really helps to place the science and the importance of these studies in a broader sense and why or why not humanity should pursue them.
First thing that causality/FTL paradox diagram makes me think is that our basic understanding of causality may be inaccurate. That's the first place my brain reaches for. It's like running through an equation that you already know the answer to but coming up with the wrong answer. You know the answer you got is wrong because you know what the answer already is, you're just working through the scenario the equation presents. In life, when it comes to problems involving perception of any kind, I've learned that the first place you always want to look is at the human error factor. I'm no quantum physicist or math wizard, sure. But when you know the answer you're coming up with doesn't match the answer you know to expect, do you blame the problem or do you double check your work? Or to simplify it, when you take a measurement and then cut something to length and it doesn't work, do you check the measurement or do you check the cut length? Problem then becomes that we don't have a cheatsheet to refer back to and there's no way to run a real world version of it to see how we get to the answer. At least not yet.
There was a PBS Space Time video where the narrator proposed that the decreased progress in quantum mechanics may be due to the fact that we may have to consider a completely different outlook on how we see the universe. For all we know we might've reached a dead-end given the knowledge and mathematical formulas we have. We're trying to apply macroscopic rules onto subatomic events that we cannot properly measure, so our intuition fails us time and time again. Or as someone else said, "if your only tool is a hammer then everything looks like a nail."
your problem with this diagram lies entirely within vibes. if you want a reason to disagree you have to come up with a reason, not just say "idk why but it feels like this is wrong somehow". as far as we know, it's not, but if you have any theories to the contrary go collect your nobel prize
@@april5054 You have to come up with a hypothesis before delving deeper. We're at a point in QM where things are stagnating, so it's only reasonable to try and approach it from a different perspective. He may be wrong, who knows, but without trying or at least attempting to think 'outside the box' no progress will be made.
I think a possible sollution to the time travel paradox is a system like we have seen it in the show Dark. The reason why you cannot change anything by traveling through time is because the events always included you traveling in the past. Meaning that the ship sending back the order to turn out ftl communication happened in the original time line as well, and was there ignored. So, the idea that time paradoxes are impossible is that actions of time travel always happened and this cannot change the outcome.
@@timdefauconval8182 Haven't thought too deeply about it, but I think so. If a time travel exist, and he has always made the impact in the past, it means he will have to always travel back into the past in the future, making it a deterministic universe where everything is set in stone, from every decision of intelligent life down to each quantum state that defines the future.
Yes, this is Nietzsche's ideo of eternal recurrence. Everything that has happened will happen again, and what will happen has already happened an infinite number of times. A-la, "time is a flat circle."
@jaceygaither2581 well, yes and no. As far as I understand Nietzsche here, the cycle of time is the entire history, while the time travel here only limits that cyclic idea to actual time travel, which is the exeption. So, while for the time travel causality, it will be a repeating ring, the rest of the universe would still follow a linear time line of causality.
I don't recall where I saw it, but there is a quote from a science fiction story I once read that applies to your final point: "The galaxy is riddled with worlds holding the ruins of dead civilizations that followed the sensible course, and never ventured beyond their home system." 😃
It's pretty likely that even if FTL is possible, you can't bend spacetime in a way to make it two parallel FTLs running in opposite directions that could break causality.
remember causality is based on spacetime if you bend space time then causality travels slower or faster inside that spacetime. thus causality is maintained even if you are FTL'ing (i think)
Considering that the ship is an observer and does not affect either the fact that the event happened or that it had been received I don’t see a problem with them receiving the warning before they see earth send the message. Remember, it’s the light traveling, not the actual event taking place.
Inevitably, if they receive the message of the supernova, before it happened, there is no causality in this, because even if they travel to the supernova at ftl speed at that point (let’s say to block it from happening) they will arrive at a time after the event happened. So you leave earth and travel to vega at STL speed, vega got the message in your perspective (but you are not there) when you get there no matter how fast you are, they will already have received the message If you travel back no matter how fast earth already sent the message, there is distortion but no causality interference.
Hmm. I had a thought earlier today, with this paradox in mind, of how an FTL system could still work. The idea I came up with is that the speed of an FTL event from A to B (say, a message _or_ a traveling spacecraft) is slowed down by differences in the relative speeds of A and B. Basically: • If A and B are moving at the same speed, then the wormhole between A and B is instantaneous • If A and B move at different relative speeds, then traveling through that wormhole takes you to the future by some amount, that is higher if A and B’s relative speed is higher. Like, the idea is that the first example (where a fast STL ship sees an effect precede its own cause) can still happen, but the second example (where the fast STL ship itself uses FTL to cause a time paradox) cannot. In that second example, the difference in Earth’s and the ship’s reference frames causes Earth’s first message to travel at a limited speed, such that even if the ship sent its response immediately, Earth would only receive it after they had sent the message in the first place
@@silent1884 You misunderstand the paradox at hand. If, in one reference-frame, an FTL event occurs, then there will _necessarily_ be some other reference-frame where that event’s effect appears to precede its cause. As such, that second reference-frame can be exploited to make the effect prevent its own cause, thus making a paradox possible.
exactly what I thought. even if the ship sent its response FTL, earth would still receive it after it had sent it. therefore I thought this video was flawed with so many logical wrongs. that I am not surprised we are not advancing much as a civilization lately.
@@newlook353 of course the FTL event is slowed down by differences in the relative speeds of A and B. thats just logical right? or am I the only one that sees that?
Well... We may be damaging our own tiny planet to the point of making a lot of species disappear, including oursleves. But, if it may reassure you, we're not going to break it and I would quite safely bet that it will still be around and teeming with life for a few billions years (untill our sun does the job !) So, we're a long way from "breaking the universe" yet... ;p
Outstanding! FTL was always a dream since watching Star Trek as a kid. The fact that we can glimpse these wonders of the universe as water filled meat sacks is truly amazing. Even if it isn’t possible, I appreciate that logic as to why is isn’t possible. Space is big. We’re living in an age of high definition discovery.
Wouldn't call humans just water filled meat sacks. We are an outstanding species that just appeared shortly on earth. Our intelligence and consciousness is a God's given gift truly. In the future I believe we'll be able to change universe to our fit
I think, if you travel forwards in space and backwards in time at the speed of light, then bw in space and fw in time, it would "feel" like instantaneous travel without breaking causality.
This seems to depend on the FTL message from the traveling ship in some way "inheriting" the worldline of the ship. But why? If the ship launched a regular sublight courier with the message, that courier would have its own independent worldline that would shift relative to Earth as the courier accelerated. If it had sent a radio message, it would have a worldline like any other photon, and the ship's velocity would instead be reflected in the redshift. This hypothetical FTL message does not seem to obey the usual worldline rules.
How could it not inherit the worldline of the ship? According to General relativity no reference frame is privileged, meaning that no reference frame is more important that another. If you can send a ftl message from the reference frame of the earth, then you can send a ftl message from the reference frame of the ship too. It just happens that a ftl signal sent in the ships reference frame looks like it's traveling back in time in earth's reference frame.
In my mind, the 'STL ship thinks...' means nothing. All that will happen is the STL ship will get to Vega, learn that in the time between when they left for Vega, and now they invented a much faster ship and they wasted years of their lives for no reason. They will also learn that the light from a supernova will pass by Vega in a few years and to watch out for it. Dosnt break anything.
I agree. The message should have its own world line. If you simplify it to instantaneous transmission, which would be the fastest possible travel, then the ship would intercept the signal, then respond. At that point the earth should recieve the signal almost instantaneously (Sans the time it takes for ship to understand and formulate a reply). So why would ftl messaging travel back in time?
Still do not see the paradox. The argument that the FTL message would go backward on the time line does not make sense. It would follow the normal time vector of the FTL message. Why would a ship moving at near C break cause this issue. I do also agree, the message should have it's own time line. It is travelling just like the message to vega had it's own line.
@@brettpeckinpaugh that's the question, what exactly is the 'normal' world line for a ftl message? Assuming it's instant, it would be perfectly parrellel with the space axis, with no travel time on the time axis. Now there's two facts about general relativity. The first is that all reference frames are valid. It doesn't matter what reference frame you use, the universe should look the same no matter what. The second, is that at high fractions of c, the space axis gets tilted. What's considered now by the spaceship is slanted through time frome the frame of reference of the earth. If you take these two facts together, it means that the spaceship is able to send an instant message in its own reference frame, which is parrellel to its own space axis. And then if you look at what that message does in the frame of reference of the earth, it goes backwards in time.
This is what I thought when he gave that as an example. Out there, the movement of the matter is everywhere. Though, gravity and other influencial force might control it, but again what's the basis as to why it was drawn that way.
that's what I was thinking, if the STL ship sends an FTL message, the line should be either horizontal, in the case that no time passed (instantaneous message) or it should be angled in the opposite direction, toward the top of the diagram, indicating that some time passed between sending the signal and receiving it. Either way, it's not clear with this Minkowski diagram how the Earth would get the STL signal back before they sent theirs. I'm skeptical of the idea that FTL causes paradoxes and I feel like this is a bad example of FTL causing a paradox. :)
Flip your phone/head so that the STL ship’s space axis is the horizon. That is why the stl message is drawn like that, is in parallel with the ship’s space axis. I still don’t understand it anyways, but is starting to make sense
I'm not sure either, but my guess is perhaps anything sent by the STL ship has to be parallel to the STL ship's space-axis(?) Why this is the case, I really have no clue. Edit: Upon closer inspection, the two lines are not parallel, so my explanation is flat out wrong.
Id be interested to see your take on Sabrina Hofstetter's argument that FTL isn't actually ruled out in GR, and that FTL doesn't have to always result in casualty violations
I legitimately wish you could see my face the moment i notice there is a new Cool Worlds video in my subscriptions sitting there waiting for me, i love this channel so much, the work and effort that goes into every video does NOT go unnoticed, thank you for giving us such high quality brain food. oh, btw, I NEED MORE lol.
You always sound so dramatic and yet extremely clear, scientific and well spoken in your explanations. Love watching and listening. Thanks professor Kipping, for the work and the stories.
My two cents, on traveling back in time... The Past is Not Static: Time is continuously flowing forward, so events in the past are not stationary moments waiting to be revisited. Once something has happened, it cannot be paused or accessed again as if it were fixed in place. Impractical Speed of Travel: Even if time travel were possible, the act of traveling backward would take "some" time. By the time you reach the past you desire, the event you're trying to change would have already initiated, moved forward and/or concluded, making intervention impossible. Logical Incoherence: Time cannot be rewound like a location. Traveling through time is fundamentally different from traveling through space, and trying to access past events contradicts the nature of time’s continuous progression.
I have an affinity for how this gentleman explain science jargon in elucidating terms to the lay person and makes it also both profoundly educational and entertaining. He's never ever boring.
I may be missing something entirely here, and this may be an incredibly stupid question, but... Wouldn't traveling FTL away from Earth simply go back in the Earth's light cone, so that looking back at Earth, you'll see it in the past, much the same as we are looking into the past when we look at stars? Conversely, wouldn't moving FTL _towards_ Earth go forwards in its light cone? Wouldn't it just be like rewinding or fast-forwarding a movie - but interacting with it is another matter? Let's say you travel FTL to 80 or so light years from Earth. It takes you 30 minutes to get there. You look back, and you see the rise of Hitler - but according to your clock, it's 80 years + 30 minutes later. Wanting to stop WWII, you immediately send a message using an FTL messaging device back towards earth, so it gets there in 30 minutes. But why would that message not go back the other way through the light cone? When it arrived on Earth, wouldn't it be 80+ light years + 1 hour in the Future? Basically, sending a message FTL will change nothing, because it's only observational; you can't actually interact with the past. What am I missing?
I am a mathematician and this is my understanding. There needs to be a transformation of the null line back in the direction of Earth when you change directions back toward Earth. All these pop sci people seem to have latched on to this theory based on dubious mathematics or something. They literally are trying to send the message in a direction rotated pi minus the original angle from straight up of how it should actually be sent, again, because of the transformation.
I work at a movie theater. So I can't answer your question entirely. But here's what I get from this... let's say you travel FTL(faster than the speed of light) to 80 or so *light* years from earth. According to OP's earth clock, it hasn't been 80 earth years, its been 80 FTL years. Earth ages at the speed of light, as all things do since its the speed of the universe(kinda) as is the norm or so we assume. To move faster than the speed of light is to move faster than time as we know it(the law of relativity, where the "time" or "age" of something is relative to the "time" or "age" of other things) A second of time on earth would be a negative second(or something like that, depends on how fast youre going.. if you go 2x speed of light) you see? If you theoretically outrun time long enough and fast enough then you end up in the past according to the theory of relativity. It's mind breaking and requires quite a bit of imagination to see it through. If time = x as the basis for aging in the speed of light. Then to go beyond the speed of light is less than x of earth time lets say x-y, y being the negative time passed on earth while you jettison through the galaxy... I'm too uneducated to define x, and nobody i know seems to define y. Y is just less than x because y is relatively faster than x. You keep going faster than x and you end up in time travel land. It's all theoretical and I can't defend it but I understand it sorta. Quantum mechanics hasn't yet broken the speed of light, leading to further skepticism about FTL machines. This is simply a thought experiment thus far. If breaking the speed of light wall were possible, it would undermine much of what we know to be true. Stephen Hawking even hosted a time traveler party once, and encouraged all time travelers to join his party. Nobody showed up. If we end up breaking the current laws of physics and can travel backwards in time, nobody went to see Hawking, and all of events went as they are because we live in this timeline. Hitler existed. Khan existed. Was it worth the structural integrity of the timeline to let those atrocities live? Who is to say? I sell popcorn for a living. My understanding of theoretical physics is partially informed, and my understanding of math and physics is grossly uninformed. I hope this helped understand. I hope I wasn't entirely uninformed
My only understanding is that time is same to everywhere and everything, it's just that observation would require time as our eyes use light at reference, in other words; we use light to generate images, which in turn would require the light to travel into our position from the position of what we are observersing; in other words, FTL should only be able to slow down time to a degree (even if you travel 100x the speed of light it should only be X ÷ 100 or 1 ÷ 100 =0.01, instead of a negative). In other words, if you travel from earth 80 light years and it took you 8 years (10x speed of light FTL), both your position and the Earth should have only aged 8 years, but if you were to try observing at earth with optical observation devices, you would see 80 years (or perhaps 72 years) into the past since the light your eyes are receiving is from those times.
To make it less confusing, let's say instantaneous travel of just 1 light year; you and earth would still have the same timeframe, but due to our vision using light as a reference we should only be able to see earth as it was a year ago; since most signals and waves everything travels in speed of light, if you use non-instant mode of communication, observation, etc, it should have a time lag of 1 light year. In my opinion, if the crew of the FTL ship travels 80 light years in an instant, makes an instantaneous communication to an STL ship, the STL ship should still be living in the same time frame as the FTL ship, just with different locations. Now if an impending disaster is just 2 light years away from, let's say Earth, and the STL ship needs to relay information to Earth using non-instant comms, and it took the message more than 2 light years to reach, then Earth would be gone before they even reach the message. I don't know quantum physics but my uneducated brain can only come up with this. I hope someone with good knowledge on Quantum Physics would fill me up on the things I missed.
@@jerryalbus1492 It sounds like your conception is the same as mine - namely, clocks run the same regardless of where you are in the universe, and FTL speeds just get you there in advance of light. I guess I think of it similar to sound - a supersonic bullet will hit its target before the gun's report reaches it. Considering sound, sound waves travel through a given medium at a constant speed, similar to light (which itself is a wave through a quantum field). The speed of the source of the sound doesn't matter, and doesn't make sound wave travel faster. Rather, they doppler shift higher or lower in pitch depending on which direction the source is traveling relative to the hearer. I understand that light acts in the same fashion, which is why blue shifting or red shifting of light lets astronomers determine which direction relative to the Earth a celestial body is moving. And yet, high gravitational fields such as a black hole cause acceleration of matter and frame dragging such that local clocks run at different speeds. Maybe that's what I'm missing - I haven't yet fully grasped how time isn't a constant but rather changes relative to speed.
Maybe I missed something. Speed is not the issue. It's whoever is closest to the event hears first. The question is if you can send a message faster then the next person in line of the event. All messages will simply stack on top of each other never below. There will always a time line. What is fast today will be slow tomorrow.
That leads to an interesting theory where there's actually another time axis that tracks the flow of paradoxes. Paradoxes don't get resolved, but simply continuously flow in a time axis that we can never know. Of course, no way to know or prove it right now, but could make some great time travel logic for sci-fi!
This is the only limerick stuck in my brain from childhood. There once was a fellow from Bright Whose speed was much faster than light, He set out one day In the usual way And returned on the previous night!
Amazing video. To me everything about it was perfect. The structure, the atmosphere, the visual depiction, the music and most importantly the topic and conclusion of the video. I rarely discover such gems on here, so thank you a lot!
The whole time I'm watching this wonderful video, I'm thinking 'eh maybe it is good that life can't FTL' while being thankful it is a question we have the facilities to think about. I'm tickled by content that invokes healthy pluralistic thought. Please never stop.
2 роки тому+11
Amazing video and good food for thought. I have just a couple of questions for Prof Kipping, from just an outsider: a) If one is using the Alcubierre machine to do FTL travel, doesn't it mean that the space behind is indeed being dilated? How would the effective space required for a light wave departing from the FTL machine back to Earth be? Could the equations compensate and avoid the circumstance where causality is broken? b) In all these scenarios, an FTL machine is assumed to send a message that will depart the machine at the speed of light. However, nothing is assumed w.r.t. the Doppler effect that would be involved for the observers in the Earth. We know that for airplanes travelling faster than sound an effect called wave shock occurs. What would the equivalent be for the case of light in regards to the Doppler effect? Would this by any chance impede the transmission of such message? These two questions point out to what to me represents the "bottleneck" of time travel: the fact that an FTL traveller can exchange communications with Earth. In all these cases a normal non-relativistic mechanism seems to be considered. Could it be possible that such transmission would become impossible, or compensate somehow the gap that is introduced by FTL travel?
Only my second time seeing a video from you and only a few minutes in and just wow dude. I really like your style as a creator. Great editing and writing and narration. Subjects that reawaken the part of me that used to dream. New information I didn’t know about subjects I’ve learned about multiple times before. Really loving this channel. Probably my favorite I’ve come across in awhile.
Yea I read a lot into this topic. One of many theories I really like is to be able to reach FTL you would have to exist outside of Spacetime. With vast amounts of energy one could theoretically translate outside of Spacetime in a separate pocket dimension. In order to reach other galaxies the only real idea is the one from Event Horizon, where you fold the space. Hopefully no demons lurk in the folded space.... lol
In that case you suggest that matter or information would have the possibility to exist outside space time which is impossible, the laws of physics dictate that matter cannot be created or destroyed where taking it out of this space time would be the equivalent of destroying matter, black holes are but extremely dense objects that not a "hole" in space time but rather a secluded trap where no matter or energy could ever escape unless by hawking radiation. It should be noted that what inside a black hole is still bound to the laws of physics of our universe.
@@khunagnes1364 Not necessarily. The universe isn't just space and time. You could be inside the universe, while being outside space-time. It really depends on what form our universe takes, but imagine that the universe is a sphere and that space-time (where we are) is the surface of the sphere. Well, in this case if you go INSIDE the sphere, you-re outside space time but still in the universe. Thus, matter was not destroyed.
From a laymen: Wouldn't a time paradox lead to something like a parallel universe / alternate universe where the explorer would simply cease to exist in the current universe? Why would the universe allow itself to be broken?
The idea is that they dont break coz the paradoxes dont exist. If that why is, hypothetically, because when you try you simply convert to energy, then there you have it. We dont KNOW if the universe creates alternate timelines for structure. But maybe
GIGO. Once you assume without a basis that something is possible, any conclusion you draw is equally without a basis. If you assume that there are horses than can fly, you could explain their behavior and the lack of evidence by concluding that they and their feces must have antigravity properties and be repelled from where they can be detected. Time paradoxes require time, space and "reality" with things that can be objectively measured in time and space. The latest "scientific break through" is that kind of reality isn't true. I'm happy to be a pragmatic engineer who deals with problems that matter NOW to daily life, not one with delusions of grandeur who calls himself a scientist and doesn't.
From how I understand it, it's possible, but in the same way that anything that could be possible is. Mainly because we've just never come across any theory or experiment definitively proving, or disproving, time travel that could give us any hints about how this kind of thing would work. So, for now, there's really no way to know, unfortunately. Most of the stuff in the video are basically things that are right at the edge of how we understand the laws of the universe. A parallel universe or timeline is one step beyond that. I'm not a theoretical physicist (who only exist in theory, anyways 😉), so take what I say with a grain of salt, as with anyone on the internet.
@@OrangeC7 one of the things I thought about time travel into the past, is that the earth is spinning, while orbiting the sun. While the sun is orbiting the super blackhole at the centre of the milkyway. And the milky-way itself is moving. We are moving at tremendous speeds, which means out location is changing constantly. Even if you went one second back in time, you'd pop up somewhere in deep space far away from where earth was one second in the past. I suspect that you, or any information about you, wouldn't be be able to get back to your original location, before the moment you left. Though, you would be able to bring information with you ftl.
Matter cannot travel at the speed of light according to our current understanding of the universe. Let me explain why: 1. Einstein's Theory of Special Relativity: - As an object approaches the speed of light, its mass becomes infinite, and so does the energy required to move it. Formula used - m = m0 / [1-(v square / c square)] ^ 1/2. - This means it is impossible for any matter to go faster than light travels. 2. Energy Requirements: - Astrophysicists have discovered gas and dust in distant exploding stars moving at 99.9997 percent of the speed of light. - However, even though this amount of matter seems close to light speed, the energy needed to move even a little faster is nearly infinite. - Einstein's famous equation, E=mc², explains this: The faster an object moves, the exponentially larger amount of energy is required to speed it up. - Travelling at light speed would require an impossible amount of energy ¹. 3. Parallel Linear Time: - When matter reaches speeds near that of light, it no longer exists in "normal" time. - Instead, it enters a parallel linear time that coincides with our timeline but behaves differently. - In this state, only energy exists, and normal "matter" cannot exist without exceeding the speed of light. So, unless you're a photon, matching the universe's speed record remains a distant dream! 🌟🚀
If you switch the graph to use the STL ship as the relevent point of reference, there is no more time issues. The issue is with the rule about the axis being symetrically flipped over the null line. You need to draw a new null line from the perspective of the ftl ship, because the relative speed of light will have changed.
I agree. This causality issue seems more misunderstood than an actual problem. I think the graph makes sense as is and there is no causality breaking. Only when you try to confusing the passage of time with relativistic speeds. Ftl works on the basis that you never go ftl relatively speaking only appears to because you walk over the wall instead of around it
Yeah he didn't just break the 45, which is a relative mass limit, but went below 0 degrees which goes past time. It doesn't create paradoxes imo, so much as exceeds the state of collapse into superposition. The person would exit our Timeline (and reality) until they ended up in a new one, likely never able to return :)
I just want to mention I think a more likely explanation for why Alcubierre drives wouldn't work is simply that exotic matter (the theoretical substance with negative mass that is required for the warping to happen and we have absolutely no evidence of) simply doesn't exist imho.
In minute 15:19 , you describe the first paradox, taking into consideration that the STL ship space axis is constant trough space/time, which will only apply after the ship reaches that speed, and not before, as before departuring, the ship would be experiencing earth's space/time axis. It is just as it departs that the ship experiences its own relativistic space/time dilation, being at all times ABOVE speed of light space axis, making it IMPOSSIBLE for VEGA RECIEVING THE WARNING to be the first event. I believe thats the reason that leads to the "PARADOX". Great video i enjoy your content.
@@isteal7427 You're right. It's not a paradox at all because the ships perspective once they intercept the warning and decided to send the Turn Off messages is traveling FORWARD in their time line but back in space. That means earth will receive the message after they sent it IAW with all common sense
@@cowboybear010 I agree, no paradox. When the ship reaches Vega, the ftl has already sent the message and the event has happened. His “space axis” for the ship isn’t necessary because it doesn’t exist. The STL gets to there when it gets there physically and “perception” isn’t important. They can’t perceive the event happening anyway so they’re not going to be confused about when it happened lol
This is the part that lost me. Can someone explain why the STL ship’s space is below the null line and it’s time is above it? I understand it has to do with rule #2 but I don’t get how. You aren’t going faster than the speed of light so it’s not like the ship is physically existing in one place while it’s visual light is existing in another right?
@@kysolakonos Yep that’s what’s going on. Physically it gets to its destination after the original event and after message is received. Not really a paradox at all. He claims that they think the the event happens before the message but they can’t think that because they can’t see it anyway.
I think it’s kind of dumb to assume a warp-drive FTL would follow the same rules as a STL because a STL travels IN space and a warp-drive FTL travels WITH space without moving through time.
Thank you for this lesson! I finally have a slightly better grasp of 'world line' diagrams. I did't realize, or remember, that all "C"/ Light Speed lines are 45degrees. That helps. Now, I'm gonna look at a nice sunset to rest my brain!!
Spacetime itself can exceed this speed limit, by stretching and contracting space which itself is the concept behind the warp drive and the wormhole. This video is mostly hogwash that only deals in purely in physics currently testable by current means and not in theoretical physics. Here is a paper that deduces that FTL can be achieved: arxiv.org/pdf/2201.00652.pdf
I’m not the brightest around but due to your easy to follow diagrams and eloquent explanation I totally get it. It’s so weird. We as humans (even the really clever few) like yourself haven’t got a bloody clue what’s going on. My head hurts lol. If there is a superior life form watching us still killing each other over green bits of paper or less we probably wouldn’t even comprehend them. Like cows in a field eating grass.
That was awesome,, answered a question I've had a difficulty conceiving for so long.. it now makes sense and as always opens the door to more questions. Great video and thankyou very much..
As I found out, once incorrect physics is a theory or law, it is very difficult to get it updated. Medical science can move easier as evidence comes along. The man in this here video is posturing with confidence, and married to boot, so in England what he says is accepted. The rest of the world leaves the old country to it, and views as a curiosity.
I like to imagine that as soon as we discover FTL and break spacetime, the simulation crashes and the higher beings are annoyed they have another bug to fix
"God damn it i didnt think they would actually get to it! Now i gotta program a whole new enviorment and items"
“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.”
― Douglas Adams, The Restaurant at the End of the Universe
Na no crashes (But i like the thought) I'm thinking just level 2 of the sim. It does not crash until 999,980 like the old arcade defender game.
@@lucasmoers Can confirm. Same thing happened with my father.
human scientists are the higher beings who put a sim into effect at a higher speed than their own reality to see the future, then when paradoxes occur, they have to wind back to when it happens, and figure out what's meant to happen then, and to do that they have to study the sciences which the sim people developed, but they can't figure it out, so one frustrated technician just removes the people who did the faster than light stuff, and resumes the sim.
"The universe is not required to be in perfect harmony with human ambition." -Carl Sagan
Our physical bodies live in physical dimension out of many.
⚡️⚡️⚡️In multi-dimensions existence, causality wouldn’t be violated. Abrahamic secret texts of Jews, Christians & Muslims have hinted that “instantaneous” travel is indeed possible if we live within multiple dimensions. Each dimension has its own speed limit. When u reach certain speed, u jump into a deferent dimension & u loose direct connection to ur initial one until u slow down to within its speed limit. 🤔
Thats kind of a Captain Obvious thing for Carl to say..🤣🤣
@@letsbehonest4221 You'll be surprised how many there are who don't understand something so obvious.
Then for who is it
@ΝΙΚΟΛΑΟΣ ΗΛΙΑΚΟΠΟΥΛΟΣ not who..what ..
For its self ...
Does anyone realize how crazy it is that we can even theorize something like this
Thanks to Einstein
I mean, on a certain level it's completely intuitive. You can't shine a light at something and then arrive before the light hits it, or conversely the light we see from stars has been traveling X light years to reach us, so to travel faster than light we would travel to the source before it was sent.
But I will agree that it's crazy that we have actual equations and models for it, thanks to the work of giants (upon whose shoulders we stand).
If you think about it, maybe it is just a breach of the time line where earth after the ship send the reply to turn off the ftl transmitter, so you have a time line where the crew reply and a other where the don't receive any message because earth did not send it. So in the end 2 time line exist and no loop or paradox.
It's just the brain being brain lol, so smart it had to name himself
We usually dream bigger as humans with the knowledge we have. Just think about Egyptians about death.
The universe doesn't care if it makes sense to us.
Or does it? *Vsauce song starts to play*
That’s what I think, I have this the universe doesn’t give a shit theory, sort of like if a ball went into a time travel wormhole and out the other end and knocked itself out of the way well then you would just have two balls because the universe doesn’t give a shit.
Yes it does
@@exodus2142foolish theory
Ummm ok ??? am I supposed to be like impressed at how smart you think you are or something???? Like it was just an idea I had I don’t even know if I’m right, I’m probably not but I can admit that because I’m not you know…..up my own ass ?
There once was a young lad named Mike.
Who could run faster than the speed of light.
He took off one day,
In a relative way,
And returned on the previous night!
6.67 out of 10
@@memes.clips.mp4 How about "11/10" because a score greater than 10 is impossible.
@@MastaShredduh ackchtaly 🤓🤓☝️☝️☝️☝️
what we gotta do is rip open a hole into hell itself and travel through in these giant bubbled ships so we aren't eaten by demons
@@MastaShredduh Spinal Tap says otherwise
Well, I don't know about time travel, but a fascinating thing to think about is that if you could travel FTL and have a way to look at earth from any distance, you could go far enough away from earth to see the past.
@@rodrigues.iVery easy point to understand. We're here on Earth looking out into space. If we look at the sun we're all seeing the sun in the past, as it was 8 minutes ago because that's how long light from the sun takes to reach our eyes. So likewise, if we could instantly transport to a point next to the sun and then looked at Earth we'd be seeing Earth as it was 8 minutes ago in the past. If we could instantly transport to Alpha Centauri and stare back at Earth we'd be seeing Earth as it was over 4 years ago because that's how long it takes light to reach our eyes from that star system. Get it?
Not only that, if you then turned around and went back, you would BE in the past, and that is a simpler way to show the FTL violated causality, right?
No... Wrong
@@Yourmomh0u5e If you mean me, how exactly is it wrong?
If you move at FTL speeds you would see 'old' light once you stopped, therefore you would see the 'past' of the planet, which is why we see stars not as they are, but as they were many years ago, some stars already died, but we still see them because they're so far away that light from the time of their death has yet to reach us, same way we see planets, which reflect the light from stars. Light speed isn't instant, it's just really really fast. Thats what Lightyears are, we see a star 1 lightyear away as what it was like 1 year ago, because that's how long it takes for light to travel to our visible space. If I'm wrong, feel free to correct me, I am not omniscient, I can make mistakes, but I don't think I did here.
@@paulshlasko3608 No, because as you would get closer to earth you would see less and less into the past, @philgiffin1487 explained it perfectly, the closer you are to a planet the less the time difference would become. I explained it in my other reply more thoroughly.
"It almost seems like a cruel cosmic joke that the universe be arranged such a way that we are able to look out and glimpse its wonders and yet are trapped here by the speed of light." So well said
Like God said "You can look but you can't touch".
Blind people have eyes yet they can not see. Be grateful for what you have.
It is only a cruel joke, due to human avarice.
The concept of continuing to climb stairs to silver level, gold level, platinum level, diamond level luxury and status ...and be temtped by yet another staircase.
The fire door locks behind you and you're trapped on a dirty roof with a noisy AC compressor.
@@AKa-qi2ov Some don't have eyes.
@@chemplay866 some don’t have brains and like their own comments 😂
It's very rare and special when someone can explain such a complicated topic in an easy to understand and follow way. Thank you.
favorite channel on 'tube. needs to have as many subscribers as real academically estimated by columbia star count
In a way thats easy to understand and follow*
@@jgunther3398whatever
Except you can find a good explanation for just about anything on UA-cam.
Alcubierre drive
Krasnikov tube
Worm hole
The speed of light should really be taught as the speed of causality. The speed of light is an incidental stenographer of the speed of causality.
Yes! It’s not the right name but sadly we’re sort of stuck with it
Let's adopt Asimov's interpretation and say that light, gravity, and causality all travel at "Celeritas", a special speed that is an innate property of the universe.
Tay wtf you got some varied interests. Taught me economics and now you're prepping a physics song?
And the speed of light is a top limit in the Lorentz transformation of spacetime diagrams that cannot be exceeded !
Using FTL info transmission breaks the maths of the spacetime diagrams (square roots of negative numbers), so the conclusions of this videos do not stand :)
@@CoolWorldsLab light travels faster than sound and doesn't break casuality for a blind man. Light travelling faster than light doesn't break casuality either. The universe operates on universal time, not local time. If you want to do a video about casuality, do one on the two different speeds of sound on Mars.
I like how Terry Pratchett said it better than the way Hawking did: Everything that happens, stays happened.
I wouldn’t even bet my lunch on that smug assumption.
I like Jim Butcher's version Law For the Conservation of History. Postulating that there is a force similar to inertia for temporal events. Essentially after an event has occurred a strong force will ensure that it remains unchanged
Yeah it might be a bit naive or misunderstanding some implications of our current understanding of quantum mechanics, but it always seemed more intuitive to me that the future is set and that "change" is just a matter of viewing the universe from a different position within the spacetime and there is no need to "invent" a force preventing causality to break when the universe was already set (though this being true would probably make closed causal loops impossible).
@@mkohlhorst The "Good Doctor" Isaac Asimov described the inertia of the time stream in "The End of Eternity", an interesting read even today.
So... "Everything that happens, try to stays happened"
In the Halo extended lore (books and etc), their use of slipspace creates time paradoxes like, constantly. It's not uncommon for a ship to arrive at it's destination hours, days, or WEEKS before it left. And everyone's collective reaction to the existence of these paradoxes is just to kinda shrug, say "hey man, don't worry about it too much," and move on
That's great, i fucking love it
“Hey if we keep doing this the universe might break”
“Cool”
Every time I learn something about Halo lore it sounds completely tonally dissonant from the games I played. "John Halo is a brainwashed child soldier alongside every other Spartan, and the people who commissioned the Spartan Project belong in the Hague." "The use of slipspace at all is an existential threat to all the universe." "the UN created the Spartans to suppress rebellions with legitimate grievances" this is a space marine game about fighting aliens and being badass, what the fuck is all this genuinely horrifying secondary lore?
@@nickmalachai2227 I'm glad to see someone else say this, I feel basically the same way. The deep lore fans irk me bad, it just sucks all the wind out of the sails for one of the most fun series of games I played as a kid. Like, I actually used to enjoy wiki diving and reading some of that lore- some of it was cool- but then every time I see people get up on a pedestal about how the UNSC are some evil Nazi-equivalent authoritarian regime, "the real baddies" (Compared to the Covenant? Those genocidal maniacs? Seriously?) and the spartan child soldier stuff, it makes it feel like none of it was worth it. Like, way to ruin a series; not only are the games after Bungie moved on arguably kind of mediocre, but then the books and other secondary lore retroactively hurt the Bungie games too. There's just nothing left to enjoy. It makes me so sad.
@@HorseDe-luxe I actually like the secondary lore, for the most part, I just wish the games were tonally consistent with it.
Granted, I'm a Star Wars and Transformers fan. I'm used to worse bullshit than this.
I've thought for a some time that traveling faster than light would be totally pointless, since traveling AT the speed of light would not only get you anywhere instantly, but would take you everywhere simultaneously before a moment passes. Why go faster? You would arrive before you departed. However, this is clearly necessary to overcome the effects of time dilation if you want to be able to return to your home frame of reference. You'd need to travel just faster than the speed of light enough to arrive at the same moment you departed. Teleport. Never mind that this would require enough energy to essentially make the universe run backwards.
It's what he explains around 14:30 that is so insightful.
Serious confusion arises if you fail to keep your frames of reference distinct when applying time dilation, and as he points out, you must remember that the speed of light is the same in all frames of reference. Both time and space will bend to accommodate it's constancy.
While the rate of the passage of time is determined by velocity, we don't actually have any idea what our true velocity is, as we have nothing to compare the universe (results of the big bang) to. We can no better know what the universal time constant is than we can know where we are in existence. While this places limits on what we can know about time, the fact that the future occurs first for those traveling relatively faster indicates that time is not an integral property of matter, but some kind of overlay that matter checks in with. Travel fast enough and you'll stop checking in.
Omg this diagram finally explained why and how space and time are connected. Thank you so much. I always thought I understood this concept but I was just repeating info not fully grasping it.
You need to look at curved spacetime diagrams (this one is flat) to understand the link between space and time :)
@@w0tch thanks, I will.
@@N3KRoM3KHANIKaL Yes, I completely agree. We do not have enough information and may never get it. And relying only on math is most likely not the answer. It's a very "human" way of trying to solve things.
Even then it's still a massive stretch, we don't even know it time is linear, parallel, or circular, we can observe evidence of what we experience as the passing of time, but quantum physics seems to be bending our undersanding of the rules of time, energy and matter.
Remember 3rd law of thermodynamics, entropy "TENDS", why the word tend? Because at this point it is outside the realm of our current paradigm of awareness as well as the technological capabilities as it relates to se sensory data acquisition to be able to define that theory with a more resolute likely useful definition. Aka our current level of understanding is the first black and white television. Imagine, give it colour and increase its resolution to 8k, I'll bet its a picture you can draw a more detailed understanding from. Crude metaphore I know, but there is no such thing as the best answer, only the "currently knowable" best answer. Don't act like it's a doorway to a new world of understanding, but all the knowledge you learn is simple a small stepping stone for you to leap from into the universe of the unknown, for the purpose of stumbling upon new unseen, unknown, and untouched wonders. Big and small. Seen and currently unseeable. The final frontier is not the beginning of the last mission, but the beginning of the first mission, that never ends.
@@N3KRoM3KHANIKaL maybe so.. but that doesn’t mean we give up trying. Ever. The only real failure that exists is in not trying at all. Otherwise every attempt to find FTL or unlock the mysteries of the universe bears fruit in the end, even if ultimately that fruit is just another way in which we learned how not to make a lightbulb.
Hiya, aerospace engineering grad student here! This seems really well-researched, and yes, this _is_ an effect that happens exactly as you say - and it's also not time travel. Not in the way we conventionally think of it, anyway. This model is actually referring to _information_ travel, which is surprisingly pretty different! And no, even if you switched the FTL signal to, say, a person traveling FTL to tell the Vegans (lol vegans XD), everything still holds up to how we understand relativity. This is because this thought experiment doesn't factor in the *quantum effects of information.*
Take a pair of electrons, for example - let's make these two electrons quantum-entangled (something that can actually happen!), which is a fancy way of saying that their properties are connected and shared - when one electron does something, so does the other. We have experimentally proven that, when one electron's spin flips, so does the other - _instantaneously._ Which shouldn't be possible, so long as we assume everything is capped at the speed of light. AND this happens regardless of the electron pair's distance from one another. So in theory, if we separated these two entangled electrons across the entire Milky Way, then flipped one, the other would also flip at the exact same moment as the first. This is because with _information_ travel, there's no light-speed limit to be found - no speed limit at all, really. So when one electron flips, the information of that flip _instantly_ travels to the other electron, and so it flips at the exact same time. Crazy, right? All this just to say that, according to quantum physics, information is not bound to the rules of relativity, in regards to both space AND time.
This is exactly what happens in this thought experiment - due to the nature of the different axes of space, the information onboard the STL ship comes in all jumbled and in the wrong order, but because information doesn't actually have a given speed limit (the entangled electrons are proof of this), nothing in relativity is broken! The rest of the universe follows the horizontal axis (mostly), and causality remains unbroken - since the space axis is relative to the observer, the *perspective of the order of events can change* because _information has no given speed limit,_ it's only limited by how it's perceived - so the events themselves still happen exactly in the order they happen. The line parallel with the space axis, traveling up and down, is really an _information perception line._
Think about it this way - forget the signal. What if you had a ship that traveled at exactly the speed of light? Both its time and space axis would be at 45 degrees, and thus its perception line would also be at 45 degrees. In that frame of reference, all three events - supernova X, Earth observation of X, and Vega observation of X - would happen at the exact same time. And what if we add back in the signal, and the ship was an FTL ship? Flip the STL ship line and the STL space axis line at 14:47, and we're FTL! The perceived (note: _perceived_ ) order gets _really_ janky with this example - first, the Vegans receive the warning from Earth; then the Vegans see X; then Earth sees X; then X happens. It's almost backwards! But that's okay, because *information - and thus our perception of that information - can arrive in whatever order it wants, or rather, in the order that the frame of reference allows.* No time travel, just information travel. Just thought I should mention that, to alleviate the confusion! Physics, sadly, just _really_ doesn't like actual, real time travel. (My inner Doctor Who fan is crying)
Edit: Whoopsie, so I brought this post by my thesis advisor, aaand turns out I may be just a _wee_ bit absolutely incorrect about how transmission of information via quantum entanglement works. Say you have a pair of entangled electrons that you've measured to have a net spin of 0. If you measure one electron's spin to be some value x, due to quantum entanglement, the other electron's spin must be -x. Simple enough, right? All entanglement says is that mutually shared info is conserved. _Technically_ it means you also instantly know that the other electron's spin is some value -x once you measure the first electron to be spin x, but the pitfall for many people (including myself, sadly) is extending this logic to the _transmission_ of information. Just because an electron is entangled with another doesn't mean flipping that electron will have an instant effect on the other. Transmission of information is, much like everything else in the universe, bound to the speed of light. Physically flip an electron, and the other electron will flip after an appropriate amount of time, NOT instantly. (Note that this also is in an ideal setting, where spin only happens along a single axis - normal electrons can have spin along any axis they want, which has all sorts of brain-breaking issues that I will NOT try and summarize for both your and my sanity.)
Having said that, though, the logic of the information perception line still holds true to a degree. Proper FTL travel doesn't yet exist, so we can't properly test the effects that FTL might have on causality. The thought experiment proposed in this video calls into question some of the issues FTL might have, but this post is more calling into question the claim that what's happening is time travel. An error I made was assuming the information in this setting was quantum information, which makes no sense since this isn't really a quantum system! You find quantum info in a quantum system, which this isn't, so the information perception line is really just the perception of normal, tangible information. (And again, quantum info like everything else is bound to the speed of light. Just pointing out another error I made.)
And yes, it still looks like causality is being broken, but still only from an information standpoint. Events still carry on as they do, it's just the order of _detection_ of events that's getting weird. Which is totally fine! Harking back to the entangled electrons, if we separate the pair far enough and make enough observations in a second, communication via the speed of light would take longer than the interval between observations, meaning you can find out the other entangled electron's spin faster than the other side could tell you what that spin is. So in a bit of a backwards way to what I said earlier, information _still_ finds cheeky ways of "beating" the speed of light without actually beating the speed of light. If information can do that, then there's no reason why this doesn't extend further ie. to this thought experiment. Information gets wonky, but we already know that's okay. No time paradoxes here!
To be fully honest here, I ain't an expert in this field - I'm a hands-on build stuff kinda guy, the stuff discussed in both what I've said as well as in this video are only tangentially related to what I study. Thanks so much to all the people who've (politely) criticized my errors - y'all were the reason why I brought this to my thesis advisor in the first place. Science is all about correcting incorrect assumptions, so thanks to all of y'all for setting me straight! And feel free to point out any other errors I've made in this edit - there's only so far proofreading will get you lol
I wanted to write something similar, but you explained it much better than I ever could. TLDR: Paradoxons are always a human brain child. If they actually happen they are resolved on their own.
This implies a device can be constructed to determine absolute speed of an object. The idea of an information order can be used to distinguish the angle of a given objects space axis and the information axis. Take two ships in space, they start off docked, moving through space at some unknown fraction of the speed of light. they exchange entangled electrons and set timers for an hour. both ships then accelerate away from one another so their separation speed is .5c after an hour of observed time on one ship they flip their electron, but the on the other ship they see the electron has already flipped. they can conclude that because the electron flipped on their ship, they must have been moving at a higher lower angle to the information plane. Assuming they can observe and be alerted to the flip as you suggest, they could even calculate their angle to the information plane. Now lets say after each ship observed an hour pass they turned around and reunited. After their rendezvous they will be on the same course and speed as before but now know what that speed is compared to the information plane. They can then decelerate together to be at zero absolute universal speed. At this point our duo can do all kinds of naughty things like shine around the emittance spectrum of helium at any other observers in the universe while transmitting a signal declaring their speed as zero absolute. Of course this would allow any observer to determine their absolute speed by comparing red shift of the helium spectrum. Or our stationary ships could observe the redshift of equidistant galaxies billions of light years away and determine were the center of the universe is. The ability to take such actions is highly cursed and Einstein would not approve.
The fundamental problem here is the information axis. The universe does not actually suffer this problem or we would have declared Einstein's theory of relativity dead the moment QE electrons were observed. With accurate enough clocks we could have already determined the absolute speed of earth by using earth's rotation to generate the velocity difference.
The flawed assumption here is that QE can relocate information. QE cannot do this. Yes, the changes in a particles are instant BUT you could not differentiate the change from random chance without observing BOTH particles and comparing the results. So far as we know this observation must happen at luminal speeds. Example: some process, call it radioactive decay, simultaneously generates two entangled electrons. these electrons have an a spin sum of zero but each one has an unknown spin. you then separate these electrons from each other. you take one electron and put it threw some spin flipping machine. Now you pass your electron through a filter that sends an electron with an up spin into detector A and a down spin electron into detector B. The moment the electron hits a detector it breaks its entanglement due to the act of observation. if your electron hits the up spin detector you can know with certainty the other electron would have hit the down spin detector but the observer of the other electron would have no clue your electron was passed through the flipping machine unless you told them. Fundamentally the information of the spin the electron does not exist until observed, changing the spin state before hand changes nothing and observing the electron breaks the connection. No FTL information. Its actually comical how far entangled pairs go to generally troll anyone trying to do FTL communication with them.
@@jadenwalker6713 Neat - didn't know that! And now I do, thanks friend! I guess there's still plenty of gaps in my knowledge for now lol
You literally wasted a mile of comment space being wrong.
Physicist here, well done engineer. However, again, there is no "flow" of time as if
it is a river. Einstein postulated that all matter has it's own time clock and that
it can, and does, tick at different rates for different velocities.
I landed at the same "strict rules" conclusion back in 2007 when designing a sci-fi setting with FTL. I borrowed a bit from Douglas Adams and ended up with a version similar to one you hinted at. That any attempts to perform an action which would result in a paradox would be met with increasingly unlikely events to prevent it from occurring in the first place. Thus, before sending any FTL comms, or engaging in certain kinds of travel, you have to draw the light cones and think through the implications as shown in your video. Thanks for putting this together. It was nice to see someone think through the same things and tie it into a neat package.
I am doing a copy and paste from a quick thought I had.
"Just spitballing here, because I am not a physicist nor time traveler, but perhaps it needs to be viewed in other dimensions rather than with a 2d graph.
Say for example someone makes a device that in theory can send an FTL message. They turn it on and send a message, but nothing happens so they think it didn't work. However thinking in the infinite universes model the senders universe continued on it's time line, but the message was received in a multitude of parallel universes. They have zero clue as to where the message came from, but they received it none the less.
Or perhaps the universes have a way of keeping things tidy, so too speak. So when the FTL message is sent, how do I say this, the entire universe is sent and is no longer where it was in time. Thinking in terms of infinite universes perhaps there are as many, call them anti universes (empty spaces) in the big empty. So the universe itself where the FTL message originated instantly fills the space where the message is received thus avoiding some weird entanglement of timelines.
Sure there might be some side effects such as the Mandela effect, but that is price we pay in order to have FTL."
This is why I only travel on Bad News. 😉
I have proven that even if you ignore all paradoxes with time travel it still violates the 1st law if thermodynamics.
This is what I was thinking. I'm glad to see somebody else thought the same. I even hypothesized that that causing a paradox, that section of time is broken off and takes that space with it, like ALL of that universe at that exact time, essentially causing what would be parallel universe. Sting Theory mathematically checked out, and postulates that a multiverse exists, along with at least 11 dimensions. I think something like this videos scenario paradox happened in the Mark Wahlberg Planet of the Apes. I remember there being a video transmission they received in the beginning of the movie that was actually sent years later...
But I don’t understand, the problem seems to be STL not FTL but STL are totally possible
I think the problem is simply with the FTL going backwards in time in the graph, the thing is the FTL message would be traveling inside space itself, what we could call a fourth dimension where time is absolute, why would it be bound by general relativity, if it's breaking it in the first place?. Then on your graph you can trace it without the time dilation of the ship, thus it would be relative to the earth again and not the ship, so for the ship, their 'FTL' is actually slower than light but for the earth it's traveling faster than light
It's the only way to have possible FTL without creating time paradoxes
"The cosmic speed limit, the speed of light is so diminutive compared to a galaxy. It almost seems like a cruel cosmic joke that the universe be arranged in such a way that we are able to look out and glimpse its wonders and yet are trapped here by the speed of light. Fated to only ever peer through the bars of our cosmic prison and dream." -- This is so beautifully spoken...
That's a carl sagan quote right?
But isn't true. You don't need FTL to visit the Galaxy, as long as your speed is very close to the speed of light, your proper time slows down a lot.
For example, at 299,792,456 m/sec (just 2m/sec less than c) you can reach a destination 720 Light years away in just one month at your clock.
But for the rest of mankind, so your family, relatives and friends you are disappeared forever and no communication is possible. This is the real problem.
@@buiosoyeah that’s why it’s basically useless. The few people on board the ship or w/e is traveling would get to experience it, but upon returning the civilization probably wouldn’t even exist
I'm sorry but I.dont see a paradox here for the ftl ship. There's so much trickery and perspective here. Imagine you are on the other side of earth and you discover the country you're in has learned of an atomic bomb strike coming at them, then you see the atomic.bomb on its way, it doesn't mean the warning came first. It's just the order of information you received that's changed, not the ORDER of ACTUAL events. Why do physicists put MORE emphasis and make EM WAVES the MOST fundamental aspect of the universe but not the ACTUAL mass and energy aka atoms which emit them in the first place? Think of em waves as Carrier waves. They don't matter at all. So what if i travel faster than light and I arrive at another planet, stop, and then someone using a telescope sees the light from my body arriving later starting from near the end (where light is closest) and appearing to go back. We would know the light is just an illusion. The ACTUAL FUNDAMENTAL ATOMIC MATTER AND MASS MATTERS MORE THAN ITS EM RADIATION IT OUTPUTS. But we instead only focus on the atomic OUTPUT aka em waves and base ENTIRE THEORIES AND PHYSICAL LAWS around THE EM WAVE. Who cares about light? We've seen that atoms can "communicate" at "infinite speed" via the double split experiments. If particles can communicate faster than light they are MORE fundamental than light. Now sure information can only travel faster than light but why focus on information as if it's more fundamental than the MASS energy? Particles can communicate instantly at infinite distance, and while the information is limited at light speed, so what. Light is just em waves with no mass. Could we make life out of em waves? No. So who cares. If we did travel faster than light THEN saw the light of our travel arrive, I'm sure NO ONE would say "wait how come you're here but yet I see you still on the way?". Everyone would know that it's just an illusion. So I don't see any paradox
According to specific in general relativity. if somehow we were able to have no mass if not 99.99% time would not pass at all and travel to another galaxy would actually feel instantaneous
I watched the entire video, and I get the sense you broke the rules of your own diagram. You drew two diagonal lines at the start, indicating the speed of light. You set the premise that any line between the time axis and this diagonal line is something moving slower than light (STL). Any line between the diagonal line and the space axis are faster than light (FTL). You then start speculating about FTL transmitters able to send a message instantaneously, meaning horizontally to the right. I'm with you so far. This is where you break every rule that has been set. You draw a line that goes downward. We've not established any reason why a line would do that. Your made up transmitter can only go up to a limit of a horizontal line (instantaneous messaging). These paradoxes start popping up because you've suddenly decided this message is being sent to the past. The FTL transmitter is now a time machine for no reason.
Like I said there might be some physics I don't understand. However in the diagram you've been using, there has been zero explanation of why any line would ever go down. The established rules were that lines could only be in the STL or FTL directions. Once you start going downward you break your own rule set.
Indeed, why is the first message drawn according to earth's POV but the second one is drawn according to the ship's POV? There's no explanation for that
@@digammaf7060it's sent from the ships pov because that's where that particular message was coming from. However the original comment is correct that it doesn't make sense on this graph as if you map out time/ space for the the ships pov the line going downward would indicate that the message is sent faster than instantly from the ship back to earth. However if you send the message ftl but not faster than instantly than I don't think any causality is broken
@@tb3099 Take 3 points, the first one being the emission of signal, the second one being the relay of the signal on the ship, and the last one being the reception of the signal on earth. Place those three points in a similar configuration as in the video. From earth's POV there is a downward worldline, but if you apply the Lorentz' transform on all three points to obtain the ship's POV there is no downward worldline anymore. In fact, the downward worldline becomes an horizontal worldline, relevant with the idea that the message is transmitted instantaneously from the ship's POV. I just checked that using a graphing calculator, the original comment is not correct about that, and you are not correct about that either.
I would gladly share the Geogebra file but I don't know how.
@@digammaf7060 interesting I was trying to figure out how to do it but I don't have a graphing calculator or know what app to use on my phone. On your graph is there a point at which the ships the ships transmitter can send something faster than light but not break causality.
I will explain it to you so you can reproduce it exactly. It's not complicated.
The Earth's worldline is the line defined by x = 0 (vertical line perpendicular with the x axis). The Ship's worldline is the line defined by y = 1.18x (arbitrary speed close to the speed of the light). The light's worldline is the line defined by y = x (45deg line).
The Signal emission Ma is located at (0; 4), the Signal relay Mb is located at (3.38; 4), the Signal reception Mc is located at (0; 1.14).
Now you have the world from Earth's POV. To get the Ship's POV, we will apply the Lorentz transform on Ma, Mb and Mc. First, the speed of the referential we are using is 1/1.18 (we are using the natural units in which c = 1). According to the wikipedia page of the Lorentz transform, we should first compute a factor called Gamma which in our case is about 1.884 (remember to take c = 1 and v = 1/1.18).
Then, for each point Ma', Mb' and Mc' which are the equivalent of Ma, Mb and Mc from the Ship's POV, we can compute the coordinates like this:
Mx' = Gamma * (Mx - v*My)
My' = Gamma * (My - (v*Mx))
(I simplified the equations seen on the wikipedia page because c = 1)
We are left with:
Emission' = (-6.39; 7.54)
Relay' = (0, 2.14)
Reception' = (-1.82, 2.15)
As you can see, Relay' to Reception' is not a downward worldline from the Ship's POV, the only downward worldline is Emission' to Relay', which is a direct consequence of breaking the speed of light and not relevant. This is not worth discussing because the real issue is not the shape of the worldline: that wouldn't be a problem for causality if both message worldlines were drawn from the same perspective, and that's why I'm telling you that you are not on the right path.
The real issue here is that EVERYTHING on the diagram is drawn from Earth's POV, everything BUT that one message reply which is drawn from the Ship's POV, which doesn't make any sense at all. When you are drawing a spacetime diagram, you draw everything from the same POV. Imaging drawing the inside of a house, but for some reason that one couch is drawn as seen from the outside. This is non sensical.
When drawn correctly, the diagram is
Emission = (0; 4)
Relay = (3.38; 4)
Reception = (0; 4)
As you can see, Emission-Relay and Relay-Reception are the same line segment, which is relevant with the idea that the communication is instantaneous. When switching to the Ship's POV, both Emission-Relay and Relay-Reception are downward worldlines (since we broke the rule of the light speed then it's not surprising to see other funky things happen) but both are the same line segment, breaking no causality at all.
respect to all the cameramen who time travelled into the past to bring us footage of all their FTL ships for use in this video
Disrespect to spam ty comments👎
i love you
Oh look an original joke...
@@daytradersanonymous9955 Phd
@@MetalFan10101 phd
Whoever knows probability applied on quantum multiverse would notice one thing - future timelines are not unique, only past timeline is unique. That also means travelling into future (as we all do all the time) is unique but travelling into past is not. Meaning, if you travel back in time there is probability 0 that you would meet yourself, in fact there is a probability 0 you would meet anything you know. Because at that point in time you would (probability 1) be in a different universe that is already separated from your past timeline. You would have no control in which universe your travel would end and therefore the probability of any paradox is 0. Travelling back in time is crossing multiverse. Bigger concern is what space we would travel through, this is not just an engineering problem since we do not understand anything about the nature of space.
I think as soon as something like FTL is achieved, we'll soon learn that there is some other, infinitely stranger arbitrary limitation way beyond our grasp that we could never have even conceived of before. I have dreams about it all the time, since I was a child in fact.
Same! I think it's just a question of science. As much as i believe in science, we make a lot of hypothesis and assumptions, we are also able to calculate stuff precisely(think gravity) without actually understanding how it works exactly or at the quantum scale. We can measure stuff and make accurately predictions on things because they follow rules, even if we don't understand them at their core. With our understanding advancing we will eventually find out that there's much more hidden stuff in the universe, much more detail to the laws of physics as we know them. I'm pretty sure with time everything we deem impossible will eventually unravel itself with technology. Think about our understanding of gravity or molecules or whatever has evolved, from thinking that something doesn't allow you to leave the ground, to thinking there might be a force, to formulating an explanation to that force, to finding actual data on it and doing research. We will eventually end up finding that gravity is an illusion and happens for other reasons than we think 🤣
I like the way you think!
@@griseld As much as I like your enthusiasm, and would love for FTL and other fancy tech to happen, wanting it to happen won't make it so. The reason science is so scientific is because of intrinsic scientific value; skepticism. Being skeptical is probably a key to being a scientist. So it isn't really healthy as a scientist to start thinking that everything you know now is completely wrong because something else that people thought was right turned out to be wrong.
That kind of thinking can lead you to certain biases that can have a lot of effect on your research. Of course, pretty much all scientists and people want FTL to be possible and would love for it to be so, but also most of them know that as it stands right now, FTL is likely impossible, and, assuming they aren't researching something that could change that, they are probably working according to that. Scientific/technological progress could hit a wall tomorrow, and any advancement could freeze. Of course, that's unlikely to happen, but it is possible. It's good to be optimistic, and enthusiastic, but knowing where the potential limits are is good. I would love for FTL to be possible as I already said, but as far as we know it's either impossible or requires incredibly advanced technology that we won't have for hundreds, or maybe even thousands of years. And our current best theories suggest it's the former, but who knows? Maybe someone will create a theory of quantum gravity that will be proven, and that will allow for FTL.
What would that be like?
I wonder how much faster you would have to go to reach that barrier
15:18 If we are looking at things from the ship's crews' perspective, how can you say that the first thing the crew perceives is Vega receiving the message from Earth? How did that information get from Vega to the ship? Was it instantaneous? Doesn't this information take time to travel to the ship from Vega? Yes, the time line has reached Vega, but it hasn't reached the ship yet. In fact, it appears that the ship learns about the message from Earth to Vega when the ship arrives at Vega (this might be an artifact of the speed of the ship, and might not be true for a different speed). More importantly, according to your timeline, the STL ship thinks Vega has received the message from Earth BEFORE THE SHIP HAS LAUNCHED.
18:11 Justify the world line for the return message from the ship. No matter how I look at it, the message from the ship back to Earth arrives later, not earlier. I don't see any way to get your reply world line from any of the other lines you've drawn.
I was feeling stupid for not understanding that part of the video, but my reasoning is the same as yours. I went back and forth in the video trying to understand why the STL ship would see that vega was warned before earth even sent the message. wouldn't that require that ship to see faster than light? on the other hand, I find it far more likely that I just don't understand the use case and I'm missing something that smarter people than me have thought of xD
@@jackie.p6891 The time slice isn't about seeing events it's about them "happening" on that world line. The video is missing some crucial explanation of the STL ship and how it travels. The close to speed of light you are travelling (without FTL) time for you actually slows down and your observations of the world outside are also slowed down. Which seems paradoxical but it's what relativity tells us. So when we talk about what the ship experiences it's really just a question of it's perspective of the outside world.
A transformation into the perspective of the ship would produce a diagram where the events happening on Eartth are slowed down.
@@salbrismind The STL ship's space line should be an S shaped curve to account for acceleration to relativistic speeds and deceleration. That would change it's position on the overall chart.
If time is a constant in the equation, then no amount of space warping, special relativity, can make anything go back in time, or can make something happen before it starts. It can slow down subjective perception or slow down objective perception, but time proceeding forward, cannot go backward.
I am with you guys
I am either too dumb or a message can never travel back in time
If FTL is impossible, the upside is that the possibility of aliens attacking would be quite low.
That also includes the possibility of meeting them :(
The world could be littered with civilizations, just they might be far apart, or some might even be next to each other, and we’d never know.
If hostile aliens became aware of us through telescopes much more advanced than ours and wished, for instance, to take over this wonderful piece of "real estate", they could possibly, with their advanced technology, attack us with a virus. The virus is so small that it could be accelerated to near the speed of light without breaking any rules. Said virus could be designed to make us really smart, smart enough to change our ecosystem in their favor, and so aggressive as to cause our own downfall through constant conflict. They could then send their STL vessels with colonizers to eventually clean up the mess and take over the place. Its not really far-fetched, in my opinion!
Alien 👽 of some types can bring souls witches % for the record player ✨!? Lol it's not of today because Mars&darWtfts planet a moon to Mars!
if aliens existed the first thing i would show them is a baja blast from taco bell
@@200fpsASH Take your meds
Nothing bothers me more than knowing I will some day pass away not knowing whats out there, I'm gonna die in ignorance and there's nothing I can do about it.
Congratulations, you had my complete attention to the entire 25 minutes. Very well done video and explanation. Super interesting
He's an interesting man, I'm the same way. I can get deep into my own thoughts while listening to a video but like you, listened to it in its fullness.
I use this video to sleep
If you moved instantaneously from earth to vega, and then told someone - to instantaneously go to earth, and tell them to shut off the instantaneous transporter, they'd arrive essentially the moment you left. That's significantly faster than light speed and there's no causal issue. The whole reason the space line is the time line reflected by the null line is Because we assume the fastest speed is the speed of light, that's an emergent property of the assumption, and any relativistic effects assumed to also be reflected are affected by that original assumption.
If you bend or break space itself to accomplish moving subluminally from point A to point B in a shorter time than light could travel that's fine - if difficult, but it wouldn't allow for paradoxes to arise, you're moving slower than light in your own reference frame, from the reference frame of your starting and ending locations - it's as if they are closer not as if you are faster. If you traveled through space more traditionally as you got close to the speed of light your physical and nuclear properties slow until you reach light speed and they halt, you couldn't perceive a message arriving at your location at this speed and even if you kept a record it wouldn't be reacted to until you reached your destination, upon which even sending the message back at the same absurd speed wouldn't arrive back to earth before it was sent.
There's also the issue of spreading out if you behave like a wave at that speed, becoming red shifted as space expands with you moving through it, and if fermions and bosons behave the same way through space at those speeds - you might arrive out of sync in a catastrophic way, unless your beginning and ending points are specific distances away - regardless of how long it took you'd eventually find such a place, and even then they'd need some marvel of engineering to slow you down or put you back together once you arrived. Your mechanical interactions would stop entirely as two objects moving in the same direction at the same speed never collide, no nuclear interaction beyond perhaps making you more or less energetic in difficult to predict ways, the magnetic components would just cycle as you travel hopefully arriving in the right orientation and not becoming a tangled mess. If Everything lined up Just right, you'd arrive after experiencing no time pass yourself, it feels instantaneous to the traveler, and that's only moving At the speed of light. If you moved somehow faster - which is as absurd as constructing a machine Out of photons to propel photons faster - you can't experience less than nothing happening.
Very well written, thank you.
Maybe maybe travel at the speed of thought or smell?
You did not need the other two large paragraphs. Your first paragraph is correct in all respects, well done Human.
I agree with this comment far more than I do with the dude making the non-sensica graphs in the video
Thank you. The whole time on the video I couldn't click to the concept of the video. Sure your warning could arrive before the perception of the event, but bot before the actual happening of the event.
Yet again you combine scientific explanation with a thoughtful and beautiful message.
Thanks for one day deciding to start doing these videos, they mean a lot to me.
Same。
Why not also mix it with spiritual & religious thoughts?!
⚡️⚡️⚡️In multi-dimensions existence, causality wouldn’t be violated. Abrahamic secret texts of Jews, Christians & Muslims have hinted that “instantaneous” travel is indeed possible if we live within multiple dimensions. Each dimension has its own speed limit. When u reach certain speed, u jump into a deferent dimension & u loose direct connection to ur initial one until u slow down to within its speed limit. 🤔
I see what you did there. Or maybe what you will do there
@@the-guy-on-your-moms-couch Well played!
I like Carl Sagans son too
I'm probably just not understanding this properly, but: Shouldn't the reply from the STL ship _always_ travel *up* every possible Worldline, no matter how quickly it gets back to Earth? Drawing the reply the way you're drawing it, means that _all_ replies back to Earth (even STL ones) will break causality, because you're sending them backwards through time rather than forwards. While Earth, the ship and Vega are all moving through time at different rates, time is still passing for all three; In your example, you're drawing the reply line back to Earth as though Earth were stationary in time from the moment it sent it's message.
It seems to be that he's trying to apply relativistic rules to something that isn't actually travelling through space. I mean yeah if something could travel through space faster than the speed of light then it would go back in time, but that's not what we're talking about. A limitation of the diagram I think. Obviously the FTL message would not be going back in time.
True, this video is circular logic. It used a diagram system that assumes within its design that light is the absolute limit. IF that is true, then this diagramming system is valid. But if we discovered FTL, then this diagram system would thereafter only be about how a 'light and picture show' worked - not actual causality. We would need to return to some other system of determining events which is more akin to a classical system.
I believe you are correct. As I stated elsewhere, I think there is a logical error in shifting frames of reference. Every "slicing" line of the diagram should be at the angle of the speed of light, not at the angle of the ships' trajectory. If you use the ships trajectory, then all other items in the system would also need to be rearranged as the trajectory is now the frame of reference.
@@leewilkinson6372 The math is correct, if you allow FTL travel, certain wordlines can travel back in time if you pick the correct reference frames.
@silience4095 The math itself is just a tool and can be correct for the frame of reference. If the frame of refenece is wrong, however, the math will lead to the wrong conclusion. This is what i posit here, not that the math itself is wrong, but rather our initial assumption may be.
So i propose that our use of the tool may be incorrect, not the tool itself, if we can indulge in a metaphor. I hope this makes better sense, and I apologize that I was typing my way through my thoughts, as it were.
I'm no expert, but, it seems that the ultimate paradox of sending the messages back in time before the event happened only appears if you switch between the two frames of reference. Which you do (we are talking about material around 19 min of video). To explain, you mark the signal of supernova travelling from earth to the stl ship instantaneously as observed from the earth and then mark how the signal to switch the FTL transmitter travels from the stl ship to earth as observed by the stl ship. If you were to draw the signal lines corresponding to single observer only, they will almost overlap and be parallel. Given a slight time delay in the machine that receives and interprets the signal and sends the signal back (a computer constrained by the speed of light for example) the signal to switch off will be always slightly later. Causality violation will never occur from a point of view of a single observer and no-one would ever be able to experience it, including the machine that sends out the supernova signal and receives the switch off signal, unless they can be in two places at the same time and be able to switch between the two frames of reference freely.
This is exactly what I 100% believe. The line at 18:12 drawn down-left is impossible even if you send message at 1 million x speed of c. The lowest it can go is horizontal (right to left). Thanks for sharing!
Yeah this confused me as the message back from the ship from earths perspective should be traveling upward and left instead of downward and left. In which case no paradox happens. Earth will always send the message before the ship sends the reply.
It's because this is all wrong and your velocity has nothing to do with altering space time. Relativity proves this but everyone likes to misinterpret Einsteins findings. The epxlanation with the clock moving slower the faster you go to lightspeed was not an example of altering time. It was just an example of how the light behind you would react if you approached light speed.
THHHIIIIIIISSSS
@@naveedrehman6083the horizontal line is earth's reference frame, not the universal one (there isn't a universal one). That line is possible given the space line and the null line of the STL ship.
What is most beautiful about this video - is actually what it has done to the comments section. Look at all the wonder, the questions, the curiosity, the debate. All these wonderful human beings trying to discover - this is what I love most about humanity, we're all in this thing together :)
Have a look at the comments on some conspiracy videos. The moon landing deniers, or the flat earthers for instance.
@@pansepot1490 no don't your brain will hurt badly
@@pansepot1490I’d rather not lose the small amount of IQ points I already have. Thanks for the suggestion though!
What if the solution is a combination of two rules?
1. Anything that is going FTL cannot physically interact with anything going STL.
2. When exiting FTL, your world line is also precisely what it was before you engaged FTL. For example, an FTL ship cannot instantly travel to an STL ship, and exit out of FTL with zero relative velocity to the STL ship.
This would make the STL ship intercepting an FTL message impossible. The only way to send messages FTL is by way of literally sending a physical ship that exits out of FTL at the destination. A message that simply travels through space and can be arbitrarily intercepted by any observer is just not possible.
The FTL ship could also fly out to the STL ship at FTL, but in order for it to ever get back to Earth earlier than it left, it would have to accelerate to have a zero relative velocity to the STL ship from this example. But then that acceleration would take time, preventing it from getting to Earth before it left.
I dunno, I’m no physicist, so I feel like I have to be missing something here, because that type of restriction doesn’t feel too arbitrary to me. This could just be me not yet picturing some other diagram following those two rules that still break causality.
Seems like the isolation within FTL, and your relative velocity from your departure being conserved in the jump, both feel like they might be more of like natural consequences of how an FTL drive might actually work.
I agree with you and just said something similar in response to another. I think we collectively miss the fact that radio messages are transmitted absurdly slower than any speeds we are trying to achieve physically. So we wouldn’t “know” what happened to a vessel on the other side of successfully achieving FTL speeds unless that vessel signaled back. And how long would that take? “God only knows” as they say. That’s assuming we couldn’t return the vessel home with its findings. All wild thoughts. But science and logic tells us it’s possible. Still solving the “how”
Was just thinking about this concept of world line alterations as I was (re)watching this video. The notion of intercepting an STL message while in FTL somehow confused me/didn't seem like it should be possible in that reference point.
The last part at around 18 minutes isn't really explained well. Why is the line going back in time? I spent like 20 minutes staring at graph lines to figure it out. Basically if you extend the STL axes into the negative direction, you can draw their bounding box for 'time-positive travel' aka non time-travel, which is any point 'above' the STL space line. But because the STL axes are so skewed, there's a very unintuitively large amount of area on the earth-centered graph that represents positive time / negative space movement for the STL ship. So a ship travelling FTL from the STL frame of reference could very well travel "back in time" from an earth reference frame. A similar application of this logic is that the space axis of the STL ship is actually an FTL line in the earth frame of reference. So an FTL traveller in earth's frame would appear to be instantaneously travelling to any point in space for the STL ship. In that case, the FTL ship would exist at every point of it's travel in that moment of time for the STL observer, which is another paradox, or it would discontinuously travel from start to end in zero time. So in theory, a wormhole could actually be FTL travel in another reference frame.
When you start with this example, it then become clear why travelling faster than 'wormhole speed' results in moving backwards in time. To one frame of reference, it is a "valid" FTL velocity going forward in time, but to another frame it is moving back in time, since that's the only thing faster than moving through the 2nd frame in zero time.
Noticed the same thing, message goes back in time instead of forward in time but faster then a regular light speed message would. in instant message would be flat. this is someone between a light speed and instant but suddenly goes the wrong direction on the axis.
Cosmological and chronological paradoxes are so interesting, rather enjoyed listening to this more than I'd expected.
the hack is to listen to it like your life depends on it.
Let's start perhaps with a more modest goal: Alcubierre-style drive that targets STL flight instead of FTL. Even that would be a tremendous step forward for our civilization.
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That seems like it would be more difficult than actually achieving FTL. I would think that simply creating the warp bubble is going to be hard enough, and generating the energy levels and creating the exotic matter required is a monumental achievement in and of itself.
I disagree. What we should actually focus on is achieving relativistic STL flight directly. By my understanding, the closer the ship gets to c, the less time they experience throughout their trip (as the length between their origin and destination contracts, or as time dilation, depending on reference frame). Assuming STL travel close enough to c, one could get to almost any location within the cosmic event horizon, while only experiencing the amount of time it takes the ship to speed up and slow down from its own perspective. The only problem this results in is that all those who aren't also travelling relativistically will be left in the past by the crew of this ship by a number of years equal to the number of light years travelled (this is the effect that would be solved by FTL travel, for what it's worth).
It seems to me that an STL Alcubierre drive would remove the length contraction / time dilation effects from the crew, since they aren't actually moving, which would paradoxically possibly make the trip longer for them than if they had travelled traditionally at the same rate as their warp bubble travelled.
@@rarebeeph1783 I don't think that relativistic speeds are going to be possible for humans due to the often overlooked relativistic effect of mass dilation, not time dilation. The faster you go, the heavier you become, and there's no telling what that is going to do to the ship itself, much less its crew.
But the possible negative effects of relativistic travel might only be dealt with by warping space itself rather than accelerating to higher and higher speeds. That makes warping the most likely of ways forward, or at least the least problematic. But then there's the question of what that's going to do to the universe itself when such a warp bubble is created. Seems to me it would result in a singularity or something even worse. ;)
Edit: Cleaned it up.
As others have mentioned, the only constraint necessary for a vector to have a >= T (Time) value. The problem is that T and S axis are different for different frames of reference. The one frame can have a vector with positive T (maintaining a dot product == C), but be a negative T vector (or dot product C) when translated to a different frame of reference. I think then the problem, all vectors having a positive T (and vector dot product == C), would be solved if there was an absolute frame of reference. A possibility frame would be the expansion of the universe. If all vectors are then constrained to having a positive T (and dot product of C) on the universal frame, regardless if a vector from one frame translates into a negative T vector in another. The universal constraints would then not be violated. That also means that "time travel" would really only be within a local frame, not the universal frame. Local paradoxes resolve on the Universal Frame. I think that makes sense. And hopefully I used the correct terms; my math is old and shaky. IANAP (I am not a physicist)
A universal frame by it's nature would disproof relativity, however. But many scifi shows do use it as as explanation for why FTL is possible but doesn't break causality (hyperspace, subspace, etc).
There's an adage in scifi circles, "Relativity, Causality, FTL, pick any two".
Hyperspace does not break causality, it just abolishes relativity. Even Hawking once admitted that in sci fi interstellar travel can be made fast if the author so wishes, as FTL travel would allow an astronaut to travel many times in his career instead of max. 1 expedition. And even if that cancels relativity, so be it.
By the way, even Herbert Wells' Time Machine does not break causality. A 19th century man goes to the future, sees it and comes back to tell the story, no causality broken. Some sci fi authors do break causality to create intellectual puzzles (Harry Harrison's Time Machine Saga or William Tenn's Discovery of Morniel Mathaway) but that is a different theme altogether.
FTL does not break causality, at least in sci fi. In fact, hardly any sci fi writer breaks causality, except for a couple of authors breaking causality as intellectual puzzle (Harry Harrison's Time Machine Saga or William Tenn's Discovery of Morniel Mathaway - by the way, none of them has anything to do with space travel). FTL just abolishes relativity. Edmond Hamilton, Isaaac Asimov, you name it.
I wonder what this would imply when you take into account the fact that light might not travel the same speed in all directions.
From the messages point of view, even if it was travelling instantly it still has to travel "through" all the light emitted from the destination. If its destination is 1 light year away, while travelling towards it it will see the destination experiencing a full year. If it then turns around and looks at the source it will be a year in the past from when it left but if it immediately heads back it will not arrive a year in the past it will see the source experiencing a year in an instant and arrive at or after the time it originally left.
Well, you're describing what would happen to a message travelling at the speed of light. The whole point of the video is to look what would happen IF the message was travelling FTL, or intantaneously in the part you're refering to...
Imagine a message that would be sent right into a wormhole and directly to the ship. It wouldn't have to travel "through" anything.
@@norbertlauret8119 The message doesn't move at all, it just moves the universe around it.
@@norbertlauret8119 no, I was describing instantaneous travel. If the message was moving at the speed of light it would have taken a year to get to the destination. During that year it would see the destination experience 2 years worth of time, I.e its time moving at double speed, and then it arrived and turned around and looked at its source it would see it still at the same time when it left.
If a wormhole goes to the past then it breaks causality naturally but that's a completely different thing and makes the graphs in the video irrelevant anyway.
@@Jacxel Oh, I'm sorry. I didn't understand what you actually meant by "travelling through" and "see the destination experiencing x year(s)". My bad.
I’m in favor of the conclusion that if we encounter “paradoxes” in a scientific thought process we should consider that the concept is flawed. However, I would point out that the chart has problems when using the STL craft and it’s time slice. Even if one buys that the STL time slice is the correct angle here, it still matters where the craft is on that slice. The crew doesn’t get to instantly “know” when Vega sees things. You’d have to allow time for Vega to send the signal to the craft and by then the light from the super nova might have already reached the ship. In addition, the ship’s movement through space over the course of the events it does perceive would affect the value of this visual.
Don’t think it matters that the STL crew doesn’t know about the vega point knowing. The point of view we have is omniscient seeing how all three points interact, not just the STL craft. The problem the example is showing is if FTL Messages gets to a point prior to sending it.
Just because they didn't see something happening doesn't mean it didn't happen.
They can easily calculate the time of all the incidents.
Let us say that Vega sent an FTL signal to the ship after receiving the FTL signal from Earth. On receiving the signal, the crew(of the ship) can calculate the time of origin of the Vega signal. Then they could also calculate the time of origin of the Earth signal. Using that information they can find the time of the supernova. Now, they have the whole timeline which they can use to see the discrepancies.
Also that is not the only causality being broken. Pause the video and then look at 14:55. You can see that if the crew intercepted the warning signal, they themselves would see the warning even before the supernova happened and even before earth sent it.
@@swimmerboy172 The narrator was asking "what does the crew of the STL ship think."
@@devverma144 in regards to 14:55...the STL time slice intercepts the signal...but what are the changes that the ship/crew are at that moment in their time slice.
@@davidmccoy1378 Why would we talk about instances where nothing happens?
Let me try to explain:
We are talking about a hypothetical concept(faster than light travel).
If that hypothetical concept is possible then it would never break causality.
So we are deliberately trying to look at those (possible)scenarios that would violate causality to disapprove the concept.
Here is an example that has nothing to do with causality but maybe it will make things clearer:
If you are trying to disapprove a business that states that their armour is indestructible, you would try out scenarios where the armour is subjected to gun shots or other weapons and not the scenarios that involve the showering the armour with rose petals.
Your written script and voice work is top class, man. Documentary level for me, especially for a subject matter that I find intriguing.
My mind is blown. When you switch the communications to "instantaneous" and re-explained the diagram, everything started making sense. I have had so much trouble trying to conceptually understand these potential issues with FTL travel/communication and this has helped so much.
Still hope we figure out a way around it, though! Like you said, it's criminal to be able to see all this cool stuff out there and not actually be able to go see it ourselves.
This video misleads - as it shows jumps from future to past like its space and not time. Once you reach any point in that diagram - you can only move up (or sideways if instantaneous) but never down, same with sending messages.
It would've been useful to see that diagram from the STL ship's perspective, since it's not very clear why their reply travels at that angle
I also agree, although after a few times of piecing it together, I think this is what I came to. Under relativity, the speed of light is constant, therefore is that 45º line between the vertical of time and horizontal of space. Any observer is always going to have their own time line vertical and their own space line horizontal and the null line or speed of light line halfway between them at a 45º angle. So as someone else speeds up on your graph, their line will tip towards the right. This is their time line but their space line is also tipping up, both getting closer and closer to the null or speed of light line.
I think it gets easier to comprehend once he switches over to instantaneous messages because those are parallel to the space line. So its easy to see why a line leaving the STL ship leaves parallel to what its space line is. I think the part that I don't understand is why one instantaneous or FTL message gets placed parallel to the earth's space line and yet the return message from the STL ship is parallel to its own space line. So I get the math of why the line is that angle, but I don't understand why 2 instantaneous messages don't have lines that are themselves parallel.
Indeed. Given the diagram, isn't their reply being sent backwards? Surely their message to earth would be in a diagonal going up and left. This is because time is going forward so the path of any action should always point upwards except the instantaneous lines which are flat ? (In an angle that mirrors the light speed line).
@@danielebowman this is exactly what I’m having trouble with. Their time line is going upward, so sending or receiving should be higher from where they started. I wish I understood this better, but the paradox didn’t make sense on that graph, or could have been drawn better. I don’t know why it’s angled down.
@@MagicScorpio Time should always go up on the context of the graph. The author made a bad mistake.
@@MagicScorpio I think it's easiest to see it when you actually tip the graph to the angle of the STL ship's space angle. The time access for the ship was shown moving up and to the left through the graph. The STL ship using FTL communication back to Earth sends on it's space angle, which intersects with Earth in the past.
Humans once looked to the sky and wanted to fly above the clouds. I'm sure that seemed just as unattainable as ftl. Granted it is orders of magnitude more difficult to achieve, but I hope it's something we never give up on. Venturing a guest I'd say we're not looking at reality the correct way for ftl. It will take a totally unexpected discover that requires us to create a new model of physics and just reality in general before we can do any real work on the issue.
I think it didn’t seem impossible as we always saw birds flying. We just imitated them. But ftl has no inspiration. Maybe if we meet aliens. Or maybe if we do use ftl, we might go to a parallel world which doesn’t result in a paradox.
@@RuchiinChina well galaxies are traveling FTL already.
@@Primarycolours- true. I don’t know how I missed that
@@Primarycolours- I'm pretty sure it's not galaxies / objects that are travelling faster than light. It's space that is expanding at an increasing rate. That is one of the concepts addressed in this video, about time and space. The objects in space are still moving, but not faster than light. It's space that is expanding which we then perceive as accelerated motion. And since nothing can move FTL that's why we perceive a red shift as space is expanding... I think.
@@RuchiinChina in space times doesn't works very well, and faster than light is possible but not with our current understanding. We needs to find negative energy materials which can't be here on earth.
I like how he predicted every point where I got confused or skeptical and delivered a good answer without me ever asking anything lol
About the talk in the end about exploration without FTL, it was quite poetic, but individuals can actually experience it one day and travel to many stars, considering there is no barrier in the laws of physics that say living things can't last for billions of years. More than that, the way in which time is perceived can be drastically modified, where a million years travel can feel like a mere hour. Just imagining human-like consciousness in a digital substrate is enough to see how this things are possible
Same. I'd have a question pop into my head, and two sentences later, he was explaining it!
One problem. The Universe really doesn't like computers either.
Even if we stay our squishy selves, we can cross our galaxy in under 25 years (traveler's time, because of time dilation) going at a comfortable 1g halfway and decelerating at the same rate the other half. Even going to the edge of the universe will take under 50 years in these conditions. Maintaining that acceleration that long will require insane amounts of fuel of course (i.e. the annihilation of 600 million tons of matter and antimatter as fuel for crossing the galaxy for a 100kg payload), but it's nice to think it's "possible" in some ways.
you must not have even tried to look at the "graphs"
Looking at my cat, I cannot really fathom what she is truly thinking as she stares back at me. With this in mind, I truly have no way to imagine what a "human-like consciousness in a digital substrate" would ever feel like. I suppose it would be as alien as comparing my consciousness to that of an ant...
The key problem ;; we can't even police the Internet today ; how could we possibly prevent the misuse of time travel tomorrow - we all know , how corrupt some people are..?
I would posit that it is possible it's just all about frames of reference. You would not be able to affect anything in your personal referential past. You could observe it, but not change it. I think the diagram is off in using the frame of reference for the STL ship as the "speed" of their FTL message would be significantly "faster" than the message from Earth. The correction for this means that their message would NOT arrive prior to that of the sent message. (On the graph their message would appear to them (could they see the graph) to curve upward past the message point. Using star trek terms if you fired off a message at warp 1 its not going to travel at (warp 1 + full impulse) simply because you were going at full impulse. Basically this graph "forgets" that for all of the pink FTL lines, the straight "space" line is not straight. For them it is a curve, so if you factor that in and the flatten it back out it shouldn't violate causality. I am probably wrong somewhere, it's 2 in the morning...
Ah thank you. I was thinking that this seems very off but couldn't put it in words.
It doesn't make sense to me that the stl ship exists on a line based on the space axis...
Saying that "the line is not straight" and implying it should be straight is basically equivalent to saying "relativity is incorrect." Now, you can have FTL travel AND causality if you scrap relativity, but unfortunately, relativity looks highly likely to be true based on our current assumptions. And relativity means those strange angled paths through spacetime, where by going really fast in a frame of reference time will pass differently (seems to be experimentally true for satellites with clocks in orbit!).
(And yes, I know that the video seems to claim that relativity isn't the problem, but... it totally is, I disagree with the video on that.)
@Peter Ingraham no, what I am implying is that this graph is uses a straight line (thus treating it linearly) vis a vis space whereas the whole concept discussed involves bending or folding space. I do not think relativity presents a problem as I have discussed as I believe it sorts itself put if you discount momentum and the standard rules that apply to speed and motion as you would have to when folding space itself. Similarly to how the rules change when you approach a black hole they would change when you folded space. As such, this graph assumes that if they are traveling at (using star trek references just for ease of discussion) warp 1 and fire of a beacon at warp 1 it will be traveling at warp 2. It will not. I posit that folded space travel is a definite limiter such that you cannot increase the speed simply by initiating a launch from something going at speed. As such it would APPEAR to curve away from the perspective of the FTL ships view on the graph IN ACCORDANCE WITH RELATIVITY. Whereas it's not actually making a curve on the graph because the graph treats space as linear and FTL travel does not.
It may be right or wrong but the fact that it is showing 4 dimensional space-time on a 2 dimensional graph, it's like trying to show a 3D cube in 1D, it's simply not doable or at least it seems to me. From what I learned we are able to show a cube on a 2d sheet just because we are able to visualize the depth of the image and draw a "line behind the lines" that how we create 3d in short we are able to circumvent one dimension by imagining it so 4d can be shown in 3d, 3D in 2D, 2D in 1D, jumping from 4D to 2D doesn't make much sense and many things may not match like they should. That I think is the main problem here that there is just no way that he could show what he wants on 2D sheet. Rather than FTL I am more convinced by Einstein-Rosen bridges theory beacuse from what I know they go through additional 4th dimension of space there for not creating this paradox if its true.
(sorry for mistakes if any english isn't my first language)
Surely the ‘paradox’ stems from the problem that your graphical representation ‘calculated’ the outgoing ‘instantaneous transmission’ from the Earth’s frame-of-reference, but the incoming ‘instantaneous transmission’ from the STL ship’s frame-of-reference.
I would have thought that two instantaneous transmissions from A to B and from B to A (both sent at exactly the same time) have to follow the same path through space-time when modelled in a single frame-of-reference. Which would mean that both transmissions lines should either be parallel to the Earth’s time axis or to the STL ship’s time axis, depending upon which observer is measuring the path through space-time.
This makes sense. It’s feels like just that the STL observers may “think” that there message to earth has been received by earth before it was sent. But from earths perspective, in Earths frame of reference, Earth to STL and STL to Earth will be instantaneous. So probably like as earth receives response as soon as it sends!! Which now that I think of it, is actually close to breaking casualty.
@@SagarThorat
Breaking causality?
Assuming that it were possible to travel at twice the speed of light (2c, and without relativistic effects) to a star that was 100 light years away. You arrive there 50 years after you left Earth. You make an instantaneous transmission back to Earth. That transmission is received 50 years after you left. Causality remains.
As the travel time tends to zero, the required multiplier of c tends to infinity. Causality cannot be broken that way…
exactly you are right ! ihad the exact same doubt ! thanks for your comment !
so no casualityy is broken.
right?
I'm pretty mixed up here but doesn't the idea of instantaneous transmission inherently violate relativity? The paradox is in trying to reconcile these two concepts.
@@cavemanraveman1 Yes. Trying to explain that nothing can move faster than the speed of light by using a ‘sub-light’ spacecraft and a transmission travelling at ‘c times infinity’ (an instantaneous transmission) is, I believe, where the problem lies (Too many uncontrollable variables).
As far as I was aware, none of the ‘Warp-drive’ hypotheses allow a spaceship inside a ‘Warp Bubble’ to send any transmission (information) to the space time outside of the Bubble, and no one outside would be able to transmit in.
If the Bubble was collapsed, the spacecraft would then be exactly as it was inside the Bubble and not moving relative to it’s starting point (remember that with all of the current Warp-drive hypotheses it is the Bubble of ‘Space Time’ that is moving, and not the ship). If the ship is not moving relative to the Earth, they are both in the same frame-of-reference and hypothetical instantaneous transmissions would not destroy causality anymore than saying “good morning” to a co-worker standing next to you would.
Also:
Imagine three galaxies in a straight line, A, M (our Milky Way) and B.
A is to the left of M and B is to the right, such that A & B are receding at 0.75c in opposite directions, due to the universe’s expansion of Space-Time. How fast are they receding from each other?
Remember, General Relativity puts a speed limit on moving things, but not on the expansion of Space-Time itself.
These two galaxies are not actually ‘moving’ with respect to each other (even though they might move relative to their local group by gravitational attraction) - it is Space-Time that is expanding that is causing the increasing separation.
Also, as A will never be able to view (and hence know of the existence of) B and vice-versa, there can be no causality problems (people rarely send messages to others that they are unaware of).
It’s actually really easy to go faster than light, just make a big ball of light and attach a couple rockets to it
Genius
I try to do it by hitting the light switch while simultaneously jumping under the ceiling light bulb fitting.
after 9 years practice it feels like I'm about there.
also I got those 9 years back just because its kind of magnets
I actually just imagined myself as light going around the world in an instant and turns out I succeeded. It felt instantaneous and there were no measurable details of the event, but it was still awesome because it happened.
I have an even cheaper option. Get a mirror, then walk towards it. You are trevelling in the opposite direction the fotons reflected from the mirror, so you are travelling FTL from that light's point of view.
@@mmhetiua-cam.com/video/ZtyxJSGM3x0/v-deo.html
I enjoy that you are actually including the possibility of breaking the universe in this video. That is why we stopped increasing speed, in my warp engine space ship.
The problem with this is that the perceived time, perspective of the relative time, for the STL ship does not change the physical location of the ship. The STLs reception of the message isn't at a time, it is at a location. In the STLs location, there is a perception of time, but that does not change its absolute location. There is no paradox. Additionally, STLs space and time axis are reversed in this diagram, which is from the earth's perspective. Time relative to the STL will pass slower than time relative to the earth as it is moving incredibly fast through space relative to earth. No expert here but it doesn't take a rocket scientist to realize the proposed diagram is incorrect. Even if perspective changes and time passes relatively differently for the STL, the location doesn't. There is always an absolute location for a given object affected by time.
What you're failing to acknowledge is FYL... the message that gets sent back returns horizontally and very frustrated. Fusion crust and burnt moon pies are heavily encoded in this message. At perfect instantaneous FTL messaging actually looses the T and quickly adopts Y instead , which altered all "C"/ Light Speed lines 75degrees. FYL "fuck your life"
true story i have proof FYL
That seems correct to me, as their response would originate at the mark but necessarily be traveling \ rather than /... I feel like I just wasted 25 minutes.
Not to mention everything else on the diagram moves bottom to top along the time axis, yet he drew the response from the ship top to bottom? Lmao he broke his own diagram and is apparently too clueless to even notice it.
@@J3loodT4lon I think it's just very poorly explained why the line is drawn like that. I'm not an expert, but what I understand is that as you move very quickly in your space ship, time moves very slowly in relationship to earth. Say every 1 day you experience, 3 days on earth pass: time is essentially out of sync between the two places. Now Earth is in the future and knows about events (like the supernova) which to you have not happened yet. But with information going less than the speed of light, you could never be informed of the supernova by earth before it happens because by the time the information reached you, it would have happened. However, with FTL travel (let's say instant) 3-days-later Earth can now inform you about events which have not yet happened. If you then returned an instant FTP message, the information is now synced to your timeframe where only 1 day has past and the supernova has not occurred, and it would reach an earth where also the super nova has not occurred, informing them of future events. I think this idea is where the wrong looking line is coming from: information is essentially jumping from one timeframe to another. It's going from a place where 3 days have past to a place where 1 day has past.
Have you done the math with the actual Lorentz Transform equations? In the case of instantaneous travel, there are 3 events that occur at different locations and different times according to the two different reference frames. A message is sent from Earth the the STL ship and then back to earth both via FTL. It is absolutely vital in this situation to define the first two controls: The Earth time + location the message was sent, and the STL time + location the message was received. Once these controls are put in place, the diagram as shown no longer works (FTL breaks the rules of this diagram). However, the underlying Lorentz Transform equations are still valid. You will find an observer at a distance can witness events that are out of place, but NO message can be sent by any means before the origin, even with instantaneous travel! I have done the math several times with the correct controls, and Sabine Hossenfelder released a video that agrees with this finding.
can you send the video..... i think the dashed line of the STL space ship is wrong
@@mzrhubah, I thought so too. . . But assumed I was missing some important information.
If the message to earth was instantaneous, then wouldn’t the space line for that message be horizontal & arrive in earths future
This makes me think that the space line of a FTL massage to earth would take longer than an instantaneous message, which makes me believe that the space line would be upwards rather than downwards as shown in the diagram and arrive in the future.
I’m not a physicist to check the math, but had the same conceptual concerns. I don’t see why it would point back in Earth’s relative time.
exactly@@mzrhub ,
@user-wl2px9on8l
I'm having a lot of difficulty wrapping my head around some things here. For example, why is the space axis a mirror-flip across the null line of the world line? For the "stationary" earth I get that it would look like a mirror-flip, but why is it? Also, when the transmission is sent from the STL ship after receiving the earth transmission, why is the slope negative? I feel like having this side-by-side with a similar diagram for the STL ship's perspective (with its world line being vertical, and the others being angled) would help clear things up...
Like, I get that there's some consideration here for time dilatation, but wouldn't that be bypassed too, as using something like the Alcubierre drive, the object is not actually moving FTL, just the space it resides in is, so it wouldn't suffer time dilatation... I'm just getting confused.
This is where I'm stuck as well. I feel like the mirror line is the most critical aspect of the problem, but is also the least explained.
He says, "Now, adding the null line back on we can note the relationship that the space axis is really just a flip of the time axis around the null."
This statement is just kinda thrown out there like it might as well just be a coincidence rather than a requirement. But he's a smart guy, so I'm sure there is more to it that gets lost in the explanation.
Here is what I really don't understand. FTL travel is obviously impossible if what he's saying is true. So then why are people spending years of their lives working on possible FTL ship designs? Is it not a complete waste of time?
yep, the 'obvious' mirror flip across the null line was just thrown in there without any real explanation. I'm confused.
Whole this explanation is a little bit wrong, straight lines are from special relativity theory, but relativistic slower than light ship need to have curved lines from general relativity, so space lines of the ship is only local oriented, and not apply to the whole universe, but(to be fair) the general relativity theory allows close temporal lines that breaks causality.
If you want to a deeper explanation, check out Section 3.3 of williamsgj.people.cofc.edu/Minkowski%20Spacetime.pdf. It really comes down to Lorentz transforms. That the FTL ship is isolated during its trip doesn’t really matter, it departs and arrives in regular space time and is able to reach its destination faster than a beam of light (a beam of “causality”) can.
@@CoolWorldsLab Beam of causality ... Those are words to conjure with.
What I love here in the commentary is everyone having the freedom to express their thoughts in either direction or in neither direction. Where I stand, the whole thing is a big mind F - - K. I want “want” to believe we can break the Ftl barrier, but any basis for that desire does not include any scientific knowledge or fact at this point in time. But, it’s fun to talk about. Peace.
The more I learn about it the more pessimistic I get, for example the Alcubierre drive is only a "solution" if it only is ever allowed to move in one direction (to avoid the light cone) and there isn't a second drive going in the opposite direction. For that to be somehow mandated by the universe would violate another fundamental tenet of relativity--that there is no preferred reference frame (i.e. among other things, the laws of physics are not different in one direction than another). People might be fine with giving that up but these kinds of symmetries are very fundamental and form the foundation of science as we know it (and have been tested to death in other regards).
IMO, the impossibility of FTL causing time travel makes other stuff make *sense* too. Because what is travel into the past, really? Another way to look at is that it's a way of *changing the entire universe* (because you have to wipe out all evidence of the real past). How much energy would that take? Infinite sounds like a good answer! And how much energy does it take to accelerate matter to the speed of light (or decelerate a tachyon to the speed of light)? Infinite energy! It all just kind of works *and* provides a neat physical explanation for why we don't see time paradoxes. Whereas every attempt to justify FTL immediately runs into a whole host of problems. At some point, you just have to accept that FTL just probably isn't real.
And one final thing... not being able to go FTL doesn't mean not being able to explore the stars in your lifetime! Theoretically, you can still get as close as you like to FTL and reach anywhere you want (modulo cosmic inflation) in any finite amount of time *from your own perspective*. You just can't do it and expect things to be the same when you get there. How would that look from your perspective? As you travel faster and faster, it's like the universe shrinks in your direction of travel--everything looks "short" in that direction. By using insane amounts of energy, we can compress the whole universe (or at least the small part of it where we travel) and cheat the cosmic speed limit! The universe gets so small, having to travel below light speed really doesn't seem like that big a deal anymore. Or like someone said, "the universe is a cramped place for a neutrino." To me, that's at least as cool as any proposed FTL mechanism, and it's 100% real.
The greatest explanation so far. I've been trying for months to understand this by reading forums and watching youtube videos. None were able to explain this. I still need to understand it more intuitively instead of through looking at lines, but this definitely opened my eyes.
This is by far the best and most simply explained video so far on this. Thank you
Imagine a yellow star 10 light years away
If you were to travel at the speed of light, it would take 10 years to get there right?
lets say your friend is watching it in a telescope, 24/7
[LIGHT SPEED]
- fly to star at light speed (10 years)
- turn star purple
- fly back home
- (10 years later) you and your friend see in the telescope that the star turned purple
[FTL]
- instantly travel to star
- arrive at star 10 years in the past
- turn star purple
- you might say, well the friend would see it instantly change
- think about if instead of instant-travel, you travel with the speed of light back. toearth.. shouldnt it be purple the moment you land since you were traveling with the purple light?
- also.. what happened to all the light that was traveling to earth? think about a middle-planet only 5 light years away from. the star instead..what do they see?
--
at least how I understand it I think haha,
but. who knows maybe there is infinite universes and you just jump to some alt dimension that is 99.9999999% the same except that the star turned purple at one moment instead of the other
Wrong right away. Why do you travel in the past when travelling instantly? Just zero time passes. You arrive there at the same moment you left, not in the past. You turn the star purple, instantly go back and then 10 years later photons reach Earth and you see the star purple.
Easy champ.
The author of the video clearly had no idea what he was speaking about, and got 7 million views spouting non sense.
@@dmitriimalikov6437 this and also why slide the world line parallel to the space axis. It's almost like you have to change the rules for the paradox to take effect.
I'm not buying it. Just because the supernova remnants, Earth, Vega, and the STL ship all experience time flowing at different rates, doesn't mean that instant comms between them somehow causes signals magically to go into the past. It happens at the same real moment, with different perceptions of how long it took to prepare a response. Fundamentally, the perceived paradox comes from using a special kind of graph that seems to have been designed for the purpose of causing confusion.
More broadly, if you see a supernova and then zip over there in your Borg transwarp conduit, you will NOT go back in time and see the star before it exploded. That's just silly. You'll find supernova remnants, emitting light that you'll outrun on the way home again. No time travel. Nor does sending back info about the supernova remnants via subspace, and receiving responses about how to collect better data, somehow cause causality violations.
If you somehow outrun your last few messages home, oh well. It's like surface-mailing a postcard immediately before boarding a jet to the same destination. Or like lightning traveling faster than thunder.
The direction of the return ftl message from the stl ship is unexplained here. I would love to know the reason for that, seems like the most important part. Wonderful vid, very informative and easy to follow!
It had something to do with the local reference time line being tilted, which also felt unexplained. If the diagram is drawn based on Earth's perspective, or even some sort of objective third perspective, why would the timeline tilt at all?
It's because for the message to be ftl, it has to be under the yellow line, if the message went up, it would go over the yellow line and thus not be ftl
@tbunreall is correct.
To elaborate, we’ve measured the speed of light to be the same no matter what your velocity is, i.e., the yellow line stays put for both Earth and the ship. The only way that can happen is by time slowing down as your velocity increases. So from Earth’s perspective, time has slowed down for the ship and vice versa. That is equivalent to saying that if two objects are traveling at different velocities, their time axes will be different.
Now to get the space axis, you have to flip the time axis around the yellow line. So their space axes will also be different.
An instantaneous message has to be parallel to the space axis of the sender. The instantaneous message from Earth to the ship is parallel to Earth’s space axis while the *_RETURN_* message is parallel to the _ship’s_ space axis. Anything slower that’s still FTL has to have an angle between the yellow line and the space axis of the sender.
Please let me know if anything is unclear, it helps me learn too!
This video is incorrect and gives wrong conclusion. Draw a 45 degree from STL towards earth. You can still do FTL lower than 45 degrees but it will be above the moment when original transmission was made. Logic in this video is false
I agree it's the most important part of the video and yet it doesn't seem correct to me either.
It really does need an explaination because the whole video depends on it ! xD
And no offence but the replies you got don't convince me. Hoping for a better representation ;)
Best explanation of time travel paradoxes I've seen in a long time, thank you for this! I feel so amazed that on one hand we can theorize and explain stuff like this yet a lot of people will still doubt that we ever went to the moon.
For sure. It's like a hideo Kojima metal gear story lmao he'd right a story about some shit like this. Make a good one crew falls out time
I don't think we went to the Moon, too many variables and orbit and where it's going to be and how do we get there if you look at Apollo 13 movie with Tom Hanks they talk about the 8-ball bubble how do you get orientation when you're not on Earth
@@joehopkins6724 dude, there's a decent shout for never breaching LEO. but your argument is instantly null and void when you're bringing up hollywood movies lol.
Yeah man. I love this guy
There are still people who think the earth is flat. Even though the first circumnavigation of the earth was completed 500 years ago. The problem with time travel is if it were conventionally possible we should already have had evidence of time travelers and it would be very easy for anyone from the future to prove it. From a theoretical standpoint, M-theory is the only possible solution to the paradox I can imagine but still seems impossible to prove regardless.
I am a PhD astrophysicist. The main points of your video are incorrect. Alcubierre travel will not create temporal paradoxes. This is because the universe is moved around the ship. The ship stays in an inertial reference frame cordoned off from the remainder of the universe. Time passes the same for both the external universe and the ship. Things are only different within the Alcubierran bubble itself, but that in and of itself does not imply time travel. There is also no worry about a complex gamma in the special relativity equations because the ship is technically not moving at all. The universe is being moved around the ship.
Thanks for watching for a fellow PhD astrophysicist! Alcubierre himself concedes it violates causality and creates paradoxes, see papers linked in the description. (The point about the ship not moving is irrelevant)
@@CoolWorldsLab I believe the problem lies on how we perceive "Time x Space". If we had an "Instantaneous ship or transmitter", wouldn't "Time axis" cease to exist on that machine? Perhaps, "Time axis" collapsed onto "Space axis".
It means "Instantaneous ship or transmitter" when it comes to "STL Ship" will take "STL Ship" 's "Time axis"....which is also the "Time axis" on Earth. Nothing is violated here.
For "FTL ship/transmitter but slower than instantaneous ship" that comes to "STL ship" from "Earth sees X", it will take a little while to get to "STL ship". Also, I think you FORGOT that "Earth sees X" is also moving through "Time axis" as well and at the same time "FTL ship/transmitter but slower than instantaneous ship" is moving.
Meaning at the time "FTL ship/transmitter but slower than instantaneous ship" reached "STL ship", "Earth sees X" and "STL ship" are parallel on the "Time axis". In this case, nothing is violated also.
So even if "STL Ship" has a "Instantaneous transmitter" to send a "Message" back to Earth, it doesn't matter cuz the "Time axis" on the "Message" cease to exist.
Earth is always parallel with "STL ship" on the "Time axis". "FTL ship" or "Instantaneous ship" 's timeline doesn't matter at all because it never goes under "Space axis".
@@CoolWorldsLabhey, i have a question. i know the vid is a year old, but if you see this, a reply would mean much to me. you said that the „time slice“ (the line that determines the causality) need to be parallel to the space axis. but that way for the stl ship, the time slice doesn‘t follow the direction of the stl ship‘s time. wouldn’t it make more sense to move it perpendicular to the time axis? i‘m sure i‘m wrong, but i don’t get why. also why is the space line flipped and what does it even say? it‘s not like the stl ship exists in a separate dimension, right? are there any materials i could look at?
Thank God. Common sense.
Attempting the impossible almost always brings great discoveries even if it's not the one that is being sought
Also leads you to fall off a cliff
@@MyKharli As a former rock climber I can tell you that as long as you are properly belayed go for it
what even is an "impossibility?"
well in this case there is nothing to attempt, speed of light is fundamental part of spacetime .. going faster follows same logic as lifting chair up while sitting on it
18:44 This paradox will never happen. Thats the point, it will always be a closed loop. Similar to Delayed Choise Quantum Eraser experiment. It is the same thing... I know it is hard to understand, but yeah, FTL is possible, time travel as well and it does not lead to paradoxes ! U can imagine it as those events are linked in time and they always happen (forming a closed loop), no matter what you will do between those events. Also on quantum level in very short times, the causality breaks down... You can apply this to whole universe. And yes, time paradoxes are not possible :-) as Steven Hawking said. Also, what do you think about the UAPs ? I would say they use FTL travel without a problem and some nonsence about causality does not bother them :D.
This video made me think of a really enjoyable sci-fi novel I once read, called "The Depths of Time". In it, humanity has the ability to use artificial wormholes to traverse the galaxy. These wormholes *also* traverse time. Since they only have STL ships, they travel at sublight speeds (with the entire crew/passengers in stasis) for upwards of say, 100 years to the 'up' end of a wormhole, traverse through it which takes them a great distance and 200 years into the past, then travel at sublight for another 100 years (plus maybe a couple weeks) to their destination. Thus, arriving thousands of light years away only two weeks after they left. To enforce against time paradoxes, there is a highly armed and technological 'guard dog' type of group that protects these wormholes, and ships that use them have their communication systems highly encrypted/deactivated so they cannot communicate with the outside universe while they are in 'their own past'. It's also interesting engineering, as although the ships may have chronologically only been in service for a few decades, they may have tens of thousands of years of travel on their internal chronometer...
Sounds like a good book! The writer Roger MacBride Allen also seems to be be someone I should check so I bought the book.
Thanks for commenting this, I just enjoyed a great trilogy because of your comment!
@@master_wayki May I ask what trilogy? Is the one I mentioned part of a trilogy? If so, I didn't know this and need to add a couple more to my kindle library!
@@falsfire try "Time" and "Space" by Stephen Baxter
@@falsfire just saw that you replied. Yes! "The Depths of Time" is part of a trilogy. The other two are "The Ocean of Years" and "The Shores of Tomorrow" in the "Chronicles of Solace" trilogy. I ended up having to buy those two because no library for hundreds of miles had a copy of either. Very, very top-notch books! They drew me in like no other books had done for years.
Sir, I only found out about you less than a month ago but have almost instantly became obsessed with your content. Keep it up man, I love everything you put out.
This is the best content on youtube hands down. I rewatch these over and over , love your work.
I always love the very grounding and philosophical thoughts proposed in these videos along with the theory. Really helps to place the science and the importance of these studies in a broader sense and why or why not humanity should pursue them.
Well said.
First thing that causality/FTL paradox diagram makes me think is that our basic understanding of causality may be inaccurate. That's the first place my brain reaches for.
It's like running through an equation that you already know the answer to but coming up with the wrong answer. You know the answer you got is wrong because you know what the answer already is, you're just working through the scenario the equation presents.
In life, when it comes to problems involving perception of any kind, I've learned that the first place you always want to look is at the human error factor.
I'm no quantum physicist or math wizard, sure. But when you know the answer you're coming up with doesn't match the answer you know to expect, do you blame the problem or do you double check your work?
Or to simplify it, when you take a measurement and then cut something to length and it doesn't work, do you check the measurement or do you check the cut length?
Problem then becomes that we don't have a cheatsheet to refer back to and there's no way to run a real world version of it to see how we get to the answer. At least not yet.
There was a PBS Space Time video where the narrator proposed that the decreased progress in quantum mechanics may be due to the fact that we may have to consider a completely different outlook on how we see the universe. For all we know we might've reached a dead-end given the knowledge and mathematical formulas we have. We're trying to apply macroscopic rules onto subatomic events that we cannot properly measure, so our intuition fails us time and time again. Or as someone else said, "if your only tool is a hammer then everything looks like a nail."
your problem with this diagram lies entirely within vibes. if you want a reason to disagree you have to come up with a reason, not just say "idk why but it feels like this is wrong somehow". as far as we know, it's not, but if you have any theories to the contrary go collect your nobel prize
@@april5054 You have to come up with a hypothesis before delving deeper. We're at a point in QM where things are stagnating, so it's only reasonable to try and approach it from a different perspective. He may be wrong, who knows, but without trying or at least attempting to think 'outside the box' no progress will be made.
@@andorexurix2491 Matt O'Dowd does have a way with words when it comes to... spacetime.
Always a GREAT day when UA-cam dings you because there is a new Cool Worlds!! 🛎 👍
Absolutely 💯
Yesss
Revisting this. Professor, I just saw an article featuring your terrascope idea, featuring you, of course 😊. I was so excited for you
I think a possible sollution to the time travel paradox is a system like we have seen it in the show Dark. The reason why you cannot change anything by traveling through time is because the events always included you traveling in the past. Meaning that the ship sending back the order to turn out ftl communication happened in the original time line as well, and was there ignored.
So, the idea that time paradoxes are impossible is that actions of time travel always happened and this cannot change the outcome.
I'm not sure to understand everything but would this mean that the future already happened ?
@@timdefauconval8182 Haven't thought too deeply about it, but I think so. If a time travel exist, and he has always made the impact in the past, it means he will have to always travel back into the past in the future, making it a deterministic universe where everything is set in stone, from every decision of intelligent life down to each quantum state that defines the future.
Yes, this is Nietzsche's ideo of eternal recurrence. Everything that has happened will happen again, and what will happen has already happened an infinite number of times. A-la, "time is a flat circle."
@jaceygaither2581 well, yes and no. As far as I understand Nietzsche here, the cycle of time is the entire history, while the time travel here only limits that cyclic idea to actual time travel, which is the exeption. So, while for the time travel causality, it will be a repeating ring, the rest of the universe would still follow a linear time line of causality.
@@Mysterios1989What you're describing is referred to as eternalism or "block time" theory.
I don't recall where I saw it, but there is a quote from a science fiction story I once read that applies to your final point: "The galaxy is riddled with worlds holding the ruins of dead civilizations that followed the sensible course, and never ventured beyond their home system." 😃
It's pretty likely that even if FTL is possible, you can't bend spacetime in a way to make it two parallel FTLs running in opposite directions that could break causality.
remember causality is based on spacetime if you bend space time then causality travels slower or faster inside that spacetime. thus causality is maintained even if you are FTL'ing (i think)
Considering that the ship is an observer and does not affect either the fact that the event happened or that it had been received I don’t see a problem with them receiving the warning before they see earth send the message. Remember, it’s the light traveling, not the actual event taking place.
Inevitably, if they receive the message of the supernova, before it happened, there is no causality in this, because even if they travel to the supernova at ftl speed at that point (let’s say to block it from happening) they will arrive at a time after the event happened.
So you leave earth and travel to vega at STL speed, vega got the message in your perspective (but you are not there) when you get there no matter how fast you are, they will already have received the message
If you travel back no matter how fast earth already sent the message, there is distortion but no causality interference.
Somebody didn't watch the full video 😂
@@leifodoyle I know lol I really didn’t before commenting and I forgot
Hmm.
I had a thought earlier today, with this paradox in mind, of how an FTL system could still work. The idea I came up with is that the speed of an FTL event from A to B (say, a message _or_ a traveling spacecraft) is slowed down by differences in the relative speeds of A and B.
Basically:
• If A and B are moving at the same speed, then the wormhole between A and B is instantaneous
• If A and B move at different relative speeds, then traveling through that wormhole takes you to the future by some amount, that is higher if A and B’s relative speed is higher.
Like, the idea is that the first example (where a fast STL ship sees an effect precede its own cause) can still happen, but the second example (where the fast STL ship itself uses FTL to cause a time paradox) cannot. In that second example, the difference in Earth’s and the ship’s reference frames causes Earth’s first message to travel at a limited speed, such that even if the ship sent its response immediately, Earth would only receive it after they had sent the message in the first place
The idea has merit. You're basically forcing a causality fix. Or causality correction. Something to explore and does allow FTL system to exist.
What if time is "locked" in one way, meaning messages sent and received can only travel by pointing to the future, not the past?
@@silent1884 You misunderstand the paradox at hand. If, in one reference-frame, an FTL event occurs, then there will _necessarily_ be some other reference-frame where that event’s effect appears to precede its cause. As such, that second reference-frame can be exploited to make the effect prevent its own cause, thus making a paradox possible.
exactly what I thought. even if the ship sent its response FTL, earth would still receive it after it had sent it. therefore I thought this video was flawed with so many logical wrongs. that I am not surprised we are not advancing much as a civilization lately.
@@newlook353 of course the FTL event is slowed down by differences in the relative speeds of A and B. thats just logical right? or am I the only one that sees that?
Looking around, if someone were to "break the universe", I'm not entirely convinced that would be worse.
Yeah, it feels pretty broken, already.
Well... We may be damaging our own tiny planet to the point of making a lot of species disappear, including oursleves. But, if it may reassure you, we're not going to break it and I would quite safely bet that it will still be around and teeming with life for a few billions years (untill our sun does the job !)
So, we're a long way from "breaking the universe" yet... ;p
Outstanding! FTL was always a dream since watching Star Trek as a kid. The fact that we can glimpse these wonders of the universe as water filled meat sacks is truly amazing. Even if it isn’t possible, I appreciate that logic as to why is isn’t possible. Space is big. We’re living in an age of high definition discovery.
Water filled meat sacks, lol 😂
Wouldn't call humans just water filled meat sacks. We are an outstanding species that just appeared shortly on earth. Our intelligence and consciousness is a God's given gift truly. In the future I believe we'll be able to change universe to our fit
@micaiah middleton ua-cam.com/video/5q_z8BjiYng/v-deo.html - Starship Congress 2017: Miguel Alcubierre, "Faster Than The Speed Of Light"
Imagine showing this video to a 12th century peasant
I think, if you travel forwards in space and backwards in time at the speed of light, then bw in space and fw in time, it would "feel" like instantaneous travel without breaking causality.
This seems to depend on the FTL message from the traveling ship in some way "inheriting" the worldline of the ship. But why?
If the ship launched a regular sublight courier with the message, that courier would have its own independent worldline that would shift relative to Earth as the courier accelerated.
If it had sent a radio message, it would have a worldline like any other photon, and the ship's velocity would instead be reflected in the redshift.
This hypothetical FTL message does not seem to obey the usual worldline rules.
How could it not inherit the worldline of the ship? According to General relativity no reference frame is privileged, meaning that no reference frame is more important that another. If you can send a ftl message from the reference frame of the earth, then you can send a ftl message from the reference frame of the ship too. It just happens that a ftl signal sent in the ships reference frame looks like it's traveling back in time in earth's reference frame.
In my mind, the 'STL ship thinks...' means nothing. All that will happen is the STL ship will get to Vega, learn that in the time between when they left for Vega, and now they invented a much faster ship and they wasted years of their lives for no reason. They will also learn that the light from a supernova will pass by Vega in a few years and to watch out for it. Dosnt break anything.
I agree. The message should have its own world line. If you simplify it to instantaneous transmission, which would be the fastest possible travel, then the ship would intercept the signal, then respond. At that point the earth should recieve the signal almost instantaneously (Sans the time it takes for ship to understand and formulate a reply). So why would ftl messaging travel back in time?
Still do not see the paradox. The argument that the FTL message would go backward on the time line does not make sense. It would follow the normal time vector of the FTL message. Why would a ship moving at near C break cause this issue. I do also agree, the message should have it's own time line. It is travelling just like the message to vega had it's own line.
@@brettpeckinpaugh that's the question, what exactly is the 'normal' world line for a ftl message? Assuming it's instant, it would be perfectly parrellel with the space axis, with no travel time on the time axis. Now there's two facts about general relativity. The first is that all reference frames are valid. It doesn't matter what reference frame you use, the universe should look the same no matter what. The second, is that at high fractions of c, the space axis gets tilted. What's considered now by the spaceship is slanted through time frome the frame of reference of the earth.
If you take these two facts together, it means that the spaceship is able to send an instant message in its own reference frame, which is parrellel to its own space axis. And then if you look at what that message does in the frame of reference of the earth, it goes backwards in time.
18:11 "Bizarrely, it would follow a world line like this." - Would be great if you can elaborate more on what makes you draw the line that way.
This is what I thought when he gave that as an example. Out there, the movement of the matter is everywhere. Though, gravity and other influencial force might control it, but again what's the basis as to why it was drawn that way.
that's what I was thinking, if the STL ship sends an FTL message, the line should be either horizontal, in the case that no time passed (instantaneous message) or it should be angled in the opposite direction, toward the top of the diagram, indicating that some time passed between sending the signal and receiving it. Either way, it's not clear with this Minkowski diagram how the Earth would get the STL signal back before they sent theirs.
I'm skeptical of the idea that FTL causes paradoxes and I feel like this is a bad example of FTL causing a paradox. :)
Exactly my thoughts as well. For me it should follow a null line up to earth line.
Flip your phone/head so that the STL ship’s space axis is the horizon. That is why the stl message is drawn like that, is in parallel with the ship’s space axis. I still don’t understand it anyways, but is starting to make sense
I'm not sure either, but my guess is perhaps anything sent by the STL ship has to be parallel to the STL ship's space-axis(?) Why this is the case, I really have no clue.
Edit: Upon closer inspection, the two lines are not parallel, so my explanation is flat out wrong.
Id be interested to see your take on Sabrina Hofstetter's argument that FTL isn't actually ruled out in GR, and that FTL doesn't have to always result in casualty violations
I legitimately wish you could see my face the moment i notice there is a new Cool Worlds video in my subscriptions sitting there waiting for me, i love this channel so much, the work and effort that goes into every video does NOT go unnoticed, thank you for giving us such high quality brain food. oh, btw, I NEED MORE lol.
You always sound so dramatic and yet extremely clear, scientific and well spoken in your explanations. Love watching and listening. Thanks professor Kipping, for the work and the stories.
these videos are some of the best on here. Keep it up
Have you seen the site Melody Sheep?
If not check their life beyond 1,2 and 3 videos. Absolutely you will love them.
Best at hurting your brain? hehe, brilliant presentation as always.
best on here as in on UA-cam? for sure
Thanks so much, these little messages are appreciated!
@@Vile_Entity_3545you know more channels like melody sheep
My two cents, on traveling back in time...
The Past is Not Static:
Time is continuously flowing forward, so events in the past are not stationary moments waiting to be revisited. Once something has happened, it cannot be paused or accessed again as if it were fixed in place.
Impractical Speed of Travel:
Even if time travel were possible, the act of traveling backward would take "some" time. By the time you reach the past you desire, the event you're trying to change would have already initiated, moved forward and/or concluded, making intervention impossible.
Logical Incoherence:
Time cannot be rewound like a location. Traveling through time is fundamentally different from traveling through space, and trying to access past events contradicts the nature of time’s continuous progression.
I have an affinity for how this gentleman explain science jargon in elucidating terms to the lay person and makes it also both profoundly educational and entertaining. He's never ever boring.
I may be missing something entirely here, and this may be an incredibly stupid question, but... Wouldn't traveling FTL away from Earth simply go back in the Earth's light cone, so that looking back at Earth, you'll see it in the past, much the same as we are looking into the past when we look at stars? Conversely, wouldn't moving FTL _towards_ Earth go forwards in its light cone? Wouldn't it just be like rewinding or fast-forwarding a movie - but interacting with it is another matter?
Let's say you travel FTL to 80 or so light years from Earth. It takes you 30 minutes to get there. You look back, and you see the rise of Hitler - but according to your clock, it's 80 years + 30 minutes later. Wanting to stop WWII, you immediately send a message using an FTL messaging device back towards earth, so it gets there in 30 minutes. But why would that message not go back the other way through the light cone? When it arrived on Earth, wouldn't it be 80+ light years + 1 hour in the Future?
Basically, sending a message FTL will change nothing, because it's only observational; you can't actually interact with the past. What am I missing?
I am a mathematician and this is my understanding. There needs to be a transformation of the null line back in the direction of Earth when you change directions back toward Earth. All these pop sci people seem to have latched on to this theory based on dubious mathematics or something. They literally are trying to send the message in a direction rotated pi minus the original angle from straight up of how it should actually be sent, again, because of the transformation.
I work at a movie theater. So I can't answer your question entirely. But here's what I get from this... let's say you travel FTL(faster than the speed of light) to 80 or so *light* years from earth. According to OP's earth clock, it hasn't been 80 earth years, its been 80 FTL years. Earth ages at the speed of light, as all things do since its the speed of the universe(kinda) as is the norm or so we assume. To move faster than the speed of light is to move faster than time as we know it(the law of relativity, where the "time" or "age" of something is relative to the "time" or "age" of other things) A second of time on earth would be a negative second(or something like that, depends on how fast youre going.. if you go 2x speed of light) you see? If you theoretically outrun time long enough and fast enough then you end up in the past according to the theory of relativity. It's mind breaking and requires quite a bit of imagination to see it through.
If time = x as the basis for aging in the speed of light. Then to go beyond the speed of light is less than x of earth time lets say x-y, y being the negative time passed on earth while you jettison through the galaxy... I'm too uneducated to define x, and nobody i know seems to define y. Y is just less than x because y is relatively faster than x. You keep going faster than x and you end up in time travel land. It's all theoretical and I can't defend it but I understand it sorta.
Quantum mechanics hasn't yet broken the speed of light, leading to further skepticism about FTL machines. This is simply a thought experiment thus far. If breaking the speed of light wall were possible, it would undermine much of what we know to be true.
Stephen Hawking even hosted a time traveler party once, and encouraged all time travelers to join his party. Nobody showed up. If we end up breaking the current laws of physics and can travel backwards in time, nobody went to see Hawking, and all of events went as they are because we live in this timeline. Hitler existed. Khan existed. Was it worth the structural integrity of the timeline to let those atrocities live? Who is to say? I sell popcorn for a living. My understanding of theoretical physics is partially informed, and my understanding of math and physics is grossly uninformed. I hope this helped understand. I hope I wasn't entirely uninformed
My only understanding is that time is same to everywhere and everything, it's just that observation would require time as our eyes use light at reference, in other words; we use light to generate images, which in turn would require the light to travel into our position from the position of what we are observersing; in other words, FTL should only be able to slow down time to a degree (even if you travel 100x the speed of light it should only be X ÷ 100 or 1 ÷ 100 =0.01, instead of a negative). In other words, if you travel from earth 80 light years and it took you 8 years (10x speed of light FTL), both your position and the Earth should have only aged 8 years, but if you were to try observing at earth with optical observation devices, you would see 80 years (or perhaps 72 years) into the past since the light your eyes are receiving is from those times.
To make it less confusing, let's say instantaneous travel of just 1 light year; you and earth would still have the same timeframe, but due to our vision using light as a reference we should only be able to see earth as it was a year ago; since most signals and waves everything travels in speed of light, if you use non-instant mode of communication, observation, etc, it should have a time lag of 1 light year. In my opinion, if the crew of the FTL ship travels 80 light years in an instant, makes an instantaneous communication to an STL ship, the STL ship should still be living in the same time frame as the FTL ship, just with different locations. Now if an impending disaster is just 2 light years away from, let's say Earth, and the STL ship needs to relay information to Earth using non-instant comms, and it took the message more than 2 light years to reach, then Earth would be gone before they even reach the message.
I don't know quantum physics but my uneducated brain can only come up with this. I hope someone with good knowledge on Quantum Physics would fill me up on the things I missed.
@@jerryalbus1492 It sounds like your conception is the same as mine - namely, clocks run the same regardless of where you are in the universe, and FTL speeds just get you there in advance of light. I guess I think of it similar to sound - a supersonic bullet will hit its target before the gun's report reaches it.
Considering sound, sound waves travel through a given medium at a constant speed, similar to light (which itself is a wave through a quantum field). The speed of the source of the sound doesn't matter, and doesn't make sound wave travel faster. Rather, they doppler shift higher or lower in pitch depending on which direction the source is traveling relative to the hearer. I understand that light acts in the same fashion, which is why blue shifting or red shifting of light lets astronomers determine which direction relative to the Earth a celestial body is moving.
And yet, high gravitational fields such as a black hole cause acceleration of matter and frame dragging such that local clocks run at different speeds. Maybe that's what I'm missing - I haven't yet fully grasped how time isn't a constant but rather changes relative to speed.
Maybe I missed something. Speed is not the issue. It's whoever is closest to the event hears first. The question is if you can send a message faster then the next person in line of the event. All messages will simply stack on top of each other never below. There will always a time line. What is fast today will be slow tomorrow.
Time is not a thing. Its just a measurement.
No, I definitely think you're right.
That leads to an interesting theory where there's actually another time axis that tracks the flow of paradoxes. Paradoxes don't get resolved, but simply continuously flow in a time axis that we can never know. Of course, no way to know or prove it right now, but could make some great time travel logic for sci-fi!
This is the only limerick stuck in my brain from childhood.
There once was a fellow from Bright
Whose speed was much faster than light,
He set out one day
In the usual way
And returned on the previous night!
Amazing video. To me everything about it was perfect. The structure, the atmosphere, the visual depiction, the music and most importantly the topic and conclusion of the video. I rarely discover such gems on here, so thank you a lot!
Life and death situation!!! 🖐👉The Connections (2021) [short documentary] 💖🙌
The whole time I'm watching this wonderful video, I'm thinking 'eh maybe it is good that life can't FTL' while being thankful it is a question we have the facilities to think about. I'm tickled by content that invokes healthy pluralistic thought. Please never stop.
Amazing video and good food for thought. I have just a couple of questions for Prof Kipping, from just an outsider:
a) If one is using the Alcubierre machine to do FTL travel, doesn't it mean that the space behind is indeed being dilated? How would the effective space required for a light wave departing from the FTL machine back to Earth be? Could the equations compensate and avoid the circumstance where causality is broken?
b) In all these scenarios, an FTL machine is assumed to send a message that will depart the machine at the speed of light. However, nothing is assumed w.r.t. the Doppler effect that would be involved for the observers in the Earth. We know that for airplanes travelling faster than sound an effect called wave shock occurs. What would the equivalent be for the case of light in regards to the Doppler effect? Would this by any chance impede the transmission of such message?
These two questions point out to what to me represents the "bottleneck" of time travel: the fact that an FTL traveller can exchange communications with Earth. In all these cases a normal non-relativistic mechanism seems to be considered. Could it be possible that such transmission would become impossible, or compensate somehow the gap that is introduced by FTL travel?
The problem of being faster than light is you can only see darkness
Only my second time seeing a video from you and only a few minutes in and just wow dude. I really like your style as a creator. Great editing and writing and narration. Subjects that reawaken the part of me that used to dream. New information I didn’t know about subjects I’ve learned about multiple times before. Really loving this channel. Probably my favorite I’ve come across in awhile.
Then kiss him
@@twerktospec maybe I’ll just kiss you 😘
@@markjames1908 sick ass foo 😘😘😘
Chill bro Mr kipping doesn't wanna bang you
AYO
Yea I read a lot into this topic. One of many theories I really like is to be able to reach FTL you would have to exist outside of Spacetime. With vast amounts of energy one could theoretically translate outside of Spacetime in a separate pocket dimension. In order to reach other galaxies the only real idea is the one from Event Horizon, where you fold the space. Hopefully no demons lurk in the folded space.... lol
sapce time demons be like
hello there
but ye i do agree that FTL will have a diffferent space time coz blek hole :>
In that case you suggest that matter or information would have the possibility to exist outside space time which is impossible, the laws of physics dictate that matter cannot be created or destroyed where taking it out of this space time would be the equivalent of destroying matter, black holes are but extremely dense objects that not a "hole" in space time but rather a secluded trap where no matter or energy could ever escape unless by hawking radiation. It should be noted that what inside a black hole is still bound to the laws of physics of our universe.
@@khunagnes1364 what if it co exists in out space time and same as the others
Or we just frik up by using a bunch of mass to make g waves to ride
@@khunagnes1364 Not necessarily. The universe isn't just space and time. You could be inside the universe, while being outside space-time. It really depends on what form our universe takes, but imagine that the universe is a sphere and that space-time (where we are) is the surface of the sphere. Well, in this case if you go INSIDE the sphere, you-re outside space time but still in the universe. Thus, matter was not destroyed.
From a laymen: Wouldn't a time paradox lead to something like a parallel universe / alternate universe where the explorer would simply cease to exist in the current universe? Why would the universe allow itself to be broken?
The idea is that they dont break coz the paradoxes dont exist. If that why is, hypothetically, because when you try you simply convert to energy, then there you have it. We dont KNOW if the universe creates alternate timelines for structure. But maybe
GIGO. Once you assume without a basis that something is possible, any conclusion you draw is equally without a basis. If you assume that there are horses than can fly, you could explain their behavior and the lack of evidence by concluding that they and their feces must have antigravity properties and be repelled from where they can be detected. Time paradoxes require time, space and "reality" with things that can be objectively measured in time and space. The latest "scientific break through" is that kind of reality isn't true. I'm happy to be a pragmatic engineer who deals with problems that matter NOW to daily life, not one with delusions of grandeur who calls himself a scientist and doesn't.
From how I understand it, it's possible, but in the same way that anything that could be possible is. Mainly because we've just never come across any theory or experiment definitively proving, or disproving, time travel that could give us any hints about how this kind of thing would work. So, for now, there's really no way to know, unfortunately. Most of the stuff in the video are basically things that are right at the edge of how we understand the laws of the universe. A parallel universe or timeline is one step beyond that.
I'm not a theoretical physicist (who only exist in theory, anyways 😉), so take what I say with a grain of salt, as with anyone on the internet.
You mean like Event Horizon?
@@OrangeC7 one of the things I thought about time travel into the past, is that the earth is spinning, while orbiting the sun. While the sun is orbiting the super blackhole at the centre of the milkyway. And the milky-way itself is moving.
We are moving at tremendous speeds, which means out location is changing constantly.
Even if you went one second back in time, you'd pop up somewhere in deep space far away from where earth was one second in the past.
I suspect that you, or any information about you, wouldn't be be able to get back to your original location, before the moment you left.
Though, you would be able to bring information with you ftl.
Matter cannot travel at the speed of light according to our current understanding of the universe. Let me explain why:
1. Einstein's Theory of Special Relativity:
- As an object approaches the speed of light, its mass becomes infinite, and so does the energy required to move it. Formula used - m = m0 / [1-(v square / c square)] ^ 1/2.
- This means it is impossible for any matter to go faster than light travels.
2. Energy Requirements:
- Astrophysicists have discovered gas and dust in distant exploding stars moving at 99.9997 percent of the speed of light.
- However, even though this amount of matter seems close to light speed, the energy needed to move even a little faster is nearly infinite.
- Einstein's famous equation, E=mc², explains this: The faster an object moves, the exponentially larger amount of energy is required to speed it up.
- Travelling at light speed would require an impossible amount of energy ¹.
3. Parallel Linear Time:
- When matter reaches speeds near that of light, it no longer exists in "normal" time.
- Instead, it enters a parallel linear time that coincides with our timeline but behaves differently.
- In this state, only energy exists, and normal "matter" cannot exist without exceeding the speed of light.
So, unless you're a photon, matching the universe's speed record remains a distant dream! 🌟🚀
If you switch the graph to use the STL ship as the relevent point of reference, there is no more time issues. The issue is with the rule about the axis being symetrically flipped over the null line. You need to draw a new null line from the perspective of the ftl ship, because the relative speed of light will have changed.
what do you mean by "relative speed of light"?
@@lanne3484 Light traveling inside the warped spacetime bubble with the FTL ship.
I agree. This causality issue seems more misunderstood than an actual problem. I think the graph makes sense as is and there is no causality breaking. Only when you try to confusing the passage of time with relativistic speeds. Ftl works on the basis that you never go ftl relatively speaking only appears to because you walk over the wall instead of around it
Wut?
Yeah he didn't just break the 45, which is a relative mass limit, but went below 0 degrees which goes past time. It doesn't create paradoxes imo, so much as exceeds the state of collapse into superposition. The person would exit our Timeline (and reality) until they ended up in a new one, likely never able to return :)
I just want to mention I think a more likely explanation for why Alcubierre drives wouldn't work is simply that exotic matter (the theoretical substance with negative mass that is required for the warping to happen and we have absolutely no evidence of) simply doesn't exist imho.
Exotics master isn't required with the latest theories. Also, a warp bubble has been created on a micro scale by physicist during another experiment.
lol..humans so entitled sheltered spoiled narrow minded.keep thinkimg that we are the top of everything...smh
Lentz is figuring it out without exotic matter but only 99% speed of light
In minute 15:19 , you describe the first paradox, taking into consideration that the STL ship space axis is constant trough space/time, which will only apply after the ship reaches that speed, and not before, as before departuring, the ship would be experiencing earth's space/time axis. It is just as it departs that the ship experiences its own relativistic space/time dilation, being at all times ABOVE speed of light space axis, making it IMPOSSIBLE for VEGA RECIEVING THE WARNING to be the first event. I believe thats the reason that leads to the "PARADOX". Great video i enjoy your content.
Yoooo, I can't believe I understood that. Hell, I'm surprised I understood this video. Bet money I wouldn't be able to explain it though lolol
@@isteal7427 You're right. It's not a paradox at all because the ships perspective once they intercept the warning and decided to send the Turn Off messages is traveling FORWARD in their time line but back in space. That means earth will receive the message after they sent it IAW with all common sense
@@cowboybear010 I agree, no paradox. When the ship reaches Vega, the ftl has already sent the message and the event has happened. His “space axis” for the ship isn’t necessary because it doesn’t exist. The STL gets to there when it gets there physically and “perception” isn’t important. They can’t perceive the event happening anyway so they’re not going to be confused about when it happened lol
This is the part that lost me. Can someone explain why the STL ship’s space is below the null line and it’s time is above it? I understand it has to do with rule #2 but I don’t get how. You aren’t going faster than the speed of light so it’s not like the ship is physically existing in one place while it’s visual light is existing in another right?
@@kysolakonos Yep that’s what’s going on. Physically it gets to its destination after the original event and after message is received. Not really a paradox at all. He claims that they think the the event happens before the message but they can’t think that because they can’t see it anyway.
I think it’s kind of dumb to assume a warp-drive FTL would follow the same rules as a STL because a STL travels IN space and a warp-drive FTL travels WITH space without moving through time.
He talked about how warp-drives are theoretically possible with our current physics so he was basing this thought experiment after that.
Thank you for this lesson! I finally have a slightly better grasp of 'world line' diagrams. I did't realize, or remember, that all "C"/ Light Speed lines are 45degrees. That helps. Now, I'm gonna look at a nice sunset to rest my brain!!
Spacetime itself can exceed this speed limit, by stretching and contracting space which itself is the concept behind the warp drive and the wormhole. This video is mostly hogwash that only deals in purely in physics currently testable by current means and not in theoretical physics.
Here is a paper that deduces that FTL can be achieved: arxiv.org/pdf/2201.00652.pdf
I’m not the brightest around but due to your easy to follow diagrams and eloquent explanation I totally get it. It’s so weird. We as humans (even the really clever few) like yourself haven’t got a bloody clue what’s going on. My head hurts lol. If there is a superior life form watching us still killing each other over green bits of paper or less we probably wouldn’t even comprehend them. Like cows in a field eating grass.
That was awesome,, answered a question I've had a difficulty conceiving for so long.. it now makes sense and as always opens the door to more questions. Great video and thankyou very much..
As I found out, once incorrect physics is a theory or law, it is very difficult to get it updated. Medical science can move easier as evidence comes along. The man in this here video is posturing with confidence, and married to boot, so in England what he says is accepted. The rest of the world leaves the old country to it, and views as a curiosity.