Man when I started watching I was still in college, now im 30 and Matts beard is going grey. Hope the show keeps going strong for at least another decade
Hi, gravitational wave physicist here. Small correction on how LISA's interferometry works. It doesn't actually work like a physical interferometer because the lasers would become too faint at such long distances to do it the normal way. Instead, it basically times the distance a photon takes to go from one detector to the other in 1 direction, and then the interferometric pattern you would normally get is reconstructed through a technique called Time Delay Interferometry (TDI)! Sadly the data analysis for LISA is quite different from the previous ground-based detectors and everyone's slightly panicking about it
It is impressive to measure those distances with the required precision given all the gravitational influences by all the other planets (or better said: objects) in the solar system.
I love learning about space. Thank you for all that you do. I’m struggling to communicate an idea, but I’ll try my best: assuming a perspective parallel to a solar system’s migration through space, the celestial bodies orbiting the system would at times “lead” the star and at other times they would “trail” the star. From the described perspective, could this be solar systems behaving as waves? If so, this could have implications for observing other systems in space if we are close to the described perspective? One such implication is that the orbit of the planets would have an oscillating impact on the solar system’s gravitational signature. Planets would alter the signature, not unlike a wave.
I just wanna thank PBS Space Time for all the hard work and great videos they create. I didnt know any physics and now i have a deep understanding of how the universe works. You guys inspired me to learn physics. Thank you.
You don't know physics. These are all public release contents, specialized in making the public amazed. Don't be a fool. To know physics, you have to actually read.
@patentpendulum what indicates that this channel is the only research they've done? It could have been their jumping off point. More importantly, why are you such a rude thief of joy?
To Matt and the team at PBS Space-time, thank you for your years of dedication and service providing us (the general public) such an in depth and resourceful insight into quantum physics, astrophysics, and all that is space and time. I've been watching since the days of calculating what planet Mario is on to jump as high as he does. Since the previous host... You enrich my life and satisfy my intense curiosity of the universe we live in. I live for this. Thanks again, JT Gullickson. From Canada. Love and Peace
Permanent displacement in space-time suggests it’s not only elastic but also has a ‘plastic’ quality, behaving like a medium that can be permanently shaped. This also opens up the idea that space-time could have quantized properties, aligning it with quantum gravity ideas.
We already believed spacetime is quantized independently of the reasons you provided. We have believed it for decades. Hence why there is a major search for a quantum theory of spacetime.
Thank you Matt and PBS Space Time for being a place (in space time) that always provides coverage and release from the chaos and uncertainty of the world right now… no matter how bleak things can feel it always seems a little less dire when put in the context of the cosmos. Please keep making your great content ✨
I am 70 yrs old , I remember how as a child I was fascinated in my maths / physics lesson with "Simple Harmonic Motion" - the sine wave. I started my adult life as a geologist , but then I moved into IT, then Cyber security , it was through a lot of weed and simple harmonic motion , that shaped my life
Or some sci-fi technobabble to describe a super-advanced alien civilization's information storage system. "You encode information one megabyte at a time on magnetic media? The Pak-Thak Interstellar Imperium perfected gravitational spin memory to store trillions of petabytes over one hundred thousand of your years ago."
It's crazy that you're having this right now. I'm about to submit a paper. Thank you for everything. I will be sure to note all the helpful comments and wonderful teachings on BAO.
I've been looking forward to LISA since LIGO started detecting things. The precision of detecting the position of the spacecraft relative to the other two is astounding and got me thinking about something I first wondered about in my early teens, extremely-long baseline _optical_ telescopy. It's a relatively simple matter to take data from two radio telescopes on opposite sides of the Earth, do some calculations and, boom, you get the resolution of a radio telescope the size of the Earth (though with only the light-collecting ability of the area of the telescopes). You _should_ be able to do something similar with visible light, but because they're so much smaller than radio waves, you can't just collect the data and do calculations afterwards, the light has to be collected at a single location and it has to take the same amount of time to arrive. I think it's been done at smaller scales of single telescope installations, but even that's pretty difficult. I'm guessing atmospheric disturbances would make it pretty much impossible at more extreme distances. But what if there wasn't an atmosphere? You could do it on the Moon, though you'd be dealing with moon dust, and line of sight isn't all that big on the Moon anyway which would mean you'd need to add extra complexity in the form of mirrors to redirect the light over the horizon (and each one would have to be just as precisely configured as the telescopes themselves. Orbital telescopes would be best, but you'd have to be _extremely_ precise with positioning each member of the fleet relative to the detector so that the light-speed delay from each collector to the detector is exactly the same. But LISA shows that kind of precise positioning is actually possible. So imagine a small constellation of Hubbles in a polar orbit with only mirrors collecting and focusing light on a detector craft that would be orbiting perpendicular to the constellation (or maybe stuck in a Lagrange point). Orbiting them around Earth would probably be the easiest, but if we got them to orbit the sun instead, we might be able to get some _really_ high resolution imagery. I don't think we'd be able to resolve an Earth-sized planet any bigger than a single pixel, but maybe we'd get a few pixels of a Jupiter or Saturn-sized planet.
Ever since the imaging of the two black holes a few years ago. I always wondered why they couldn't do the same thing with the size of Earth's orbit around the Sun. That would be substantially higher resolution then just the size of the Earth
@@jasonharrison25 WIth radio waves, you don't even need to take the readings simultaneously, so you can get a 2 au baseline by pointing a radio telescope at an object 6 months apart. It's, unfortunately not possible to do in the visible spectrum (at least, not without using a black hole as one of your optical elements).
@@StarkRG Sure about not needing to be simultaneous? It is my understanding that when they took the measurements for the black hole images, they added very precise time marks (using atomic clocks) in order to correctly interfere the recorded signals in the computer. For interferometry you need 2 measurements of the same signal at the same time. You can not just take 2 measurements in time, let them interfere and hope for something useful.
There are two ways of achieving what you suggest here, optical VLBI it would be called I guess, and those ways explain why it has not been done before even though as you point out it is clearly a great idea. The first is to reflect back the light collected from "light capture" spacecraft towards a single "detector" spacecraft, as you suggest. This means you can measure all the light in a single location with a single "time-base", essentially the photons are all counted using the same stopwatch, so there is no question of is we are talking about the same moment in time or not. This has the obvious issue that as the capture spacecraft are placed further and further away from the detector spacecraft, diffraction effects in the optical spectrum will mean they would need to be massive. Like... really massive. Like, kilometers wide massive, each... This is highly impractical and is essentially a non-starter (at our current Kardashev scale :)). The second way is something that LISA does actually use itself, another thing you correctly picked up on. It is also done in many other experimental missions and is a rather new technique, still in its infancy (something I've worked on and still work on), and that is the idea of "optical time-transfer". This is, basically, time syncing using lasers ;). This means that you could have a whole bunch of "hubbles" with laser links between them, that essentially keeps their clock, and hence their photon counting "stopwatches" synchronised. Then the data recorded by each one can be resynchronised on the ground to form the interferometric image. This is much easier said than done of course, but the current state of the art here is limited by the clocks used themselves. The best clocks we have ever built (which can't really go to space... yet, I know the people making them and they will try :)), are still not good enough for visible spectrum interferometry, at least not without significant correction systems of which LISA will indeed be pioneering, but not anywhere near the level needed... Anyway, it seems this is the way to do it, and work is ongoing, so watch this space I guess.
So Dr. Serova was right and regular deformation due to FTL propulsion causes cumulative damage. Better limit cruising speeds to warp 5 until we can come up with variable geometry warp fields that will be able to prevent further damage.
@bananabourbonaenima I think that doesn't matter as much here because we are only concerned with surface effects since the surface of the water is like a 2D analogy of 3D space.
Made me sit up! I thought Matt said, "Thank you Raytheon for supporting PBS". That's an interesting development I thought. Ah! Raycon! (mental note to get ears checked)
Absolutely love Space Time, always comes with super creative graphics, vids that helps people like me see what's being discussed in my mind's eye. Keep up the amazing work Matt and the team
Interesting. I'm a fantasy author, and space-time is an element in my magic system. The memory of spacetime gives me an idea for a Mind+Space (the two are seen as opposite elements, so this would be a very OP ability) spell that allows the caster to read the "memory" of the space around them to see past and current events at great distances. I love when science gives me an idea.
I would love to hear an engineering analysis of LISA. Especially the relationship between orbit, mass vs. sensitivity and resolution. What limits the orbits to where they are going to be? Can it be upgraded by adding more satellites? What exactly gets upgraded? What happens when the satellites get more massive?
A black hole is by definition a memory of spacetime since the matter that created it is no longer there. There is nothing there, no matter, only the singularity. Thus - a memory.
Question: Where do gravitational waves "go"? Like do they chircle around the Universe? When you have a wave of water it ends up as energy that is transfered to the shore. Where do these waves (since they are form of energy) ultimately end? They can't propagate through the universe forever?
there is a similiar question on physics StackExchange. and the answer is pretty good. in a nutshell, they can loose energy to heating up matter, but mainly they get distributed soo thin and get redshifted so much that they don't have any effect anymore. like light
One idea I've heard for the explanation of dark matter is that black holes might leave a small, permanent kink in spacetime after they evaporate. Neat idea.
Without seeing any math on it that seems unlikely; there would have to have been a *lot* of black holes for their remains to account for 27% of the mass of the universe...
Only 4ish minutes into the video, but my new hypothesis: could the constant addition of memory by the equally constant events producing waves, be stretching the fabric of space-time itself, and therefore be at least partially responsible for the expanding nature of the universe? Fascinating stuff.
This is why they set a limit on warp speed in star trek. Stretching the space ahead and behind you makes it wrinkly and even saggy which disrupts navigation. Its one of the hazards of old age
Thank you for doing this topic. I read an article about gravity with no mass and i didn't really understand. When i finished it i thought....i hope SpaceTime does a video on this.
There's your warp-drive signature right there. Just sayin' - that sounds like a fairly plausible explanation for the, yet to be non-fiction, warp-drive signatures that all the Star Trek crews were so keen on using to follow some rogue ship after it ditched them.
Was just watching a TOE episode about how quantum mechanics can be written as a classical nonmarkovian stochastic process. Pretty neat that there are actual memory effects in gr
That was an excellent interview. My head is still attempting to unravel some parts of it lol > Back to this gravitational memory idea. The implications of that are also quite profound. The concept of space time not being elastic and not returning to a previous equilibrium after gravity effect has passed is difficult to imagine. For example as an extreme thought experiment, if a Black hole evaporated does the space-time around where it was remain stretched/warped?
Yes, gravity, and apparently warp engines can leave permanent marks on space time. That’s why you can’t travel faster than warp seven through the same region of space too many times in a row. I most of us have already seen that episode of The Next Generation.
I swear to god , I thought that also. I was going to make a similar comment , decided to scroll down and see if some one beat me to it ! Hats off to you !
I may not be able to wrap my primitive brain around many of these concepts, but they're so fascinating & important to humanity that I'll always support you guys!
Yet another excellent video! And I love the music track - sounds like an ambient track for a stealth level in a 2000s game. Would be awesome to know the artist and the name of the track. It was surprising to not see this aspect of the video being mentioned in the credits.
You see, we are starting a project in which we play pacman in space using earth as the player and those satelites are the first 3 lines of drawing a Neptune sized ghost 😂
Guys. You _have_ to talk with whoever is titling the videos. Every time the video is about spacetime, the thumbnail says “spacetime” but the title says “Space Time” (when referring to the science thing, not the show).
This is the basis for Alastair Reynolds' FTL comms called Galactic Final Memory in his book Chasm City, part of his Revelation Space series. Couldn't recommend those books enough
If we could have greater accuracy with measurements (more watts/higher frequencies needed probably) we could use singularities as a gravitational lens to probe even "deeper". Due to the inaccuracies and limitations in the present day mathematics, things like "beginning of the universe", infinite curvature/density or "no spacetime beyond singularity" are most likely glitches and misinterpretations caused by the inaccuracy. Imagine trying to record 20kHz signal with a microphone having a 100Hz max sample rate. Yeah. You'll get artifacts and glitches. So no Lawrence Krauss, virtual particles do not "come out from nothing" and neither does the universe "come from nothing" : ) Just because our maths and methods are not absolute and perfect, doesn't mean we should reflect our limitations to what we assume or interpret about reality.
What I don't understand is how LISA can maintain relative position accurately enough to then be able to detect the change from the gravitational waves.
I always thought that the assumption that spacetime is Euclidean at some distance from mass is ripe for questioning. Even a small curvature caused by mass passing by, over a large enough volume, would look like additional mass.
The only cogent and relevant comment I can make about this video is that this is the best that Matt's hair has looked in any Space Time video I've seen. Keep growing it out Matt!
To me it sounds like the memory is in the objects occupying spacetime, not in spacetime itself. Just like ramping up your sound system to max volume. After turning it back down it still plays the exact same music, but you'll hear it differently because of hearing damage.
If these 'displacement memory effects' can be measured by a free-floating system with arms long enough to detect low-frequency signals, why can't they be measured by the same Pulsar Timing Array (PTA) we used to identify the gravitational wave background?
Because the star's motions aren't well controlled. The result of a wave's passage will be a shift in position of the pulsars, but those happen all the time. To measure ,it you need a more precisely controlled arrangement.
This is not only good stuff, but crucial. At last we have a plausible way to confirm how the gravitational metric of space time might actually change after a major gravitational event. Not only should this validate GR, but also may shed light on the effects we characterise as dark energy and dark matter. Fingers crossed that we now have 'game on'.
When measured, the curvature component of the Freidmann equation is equal to zero so it shouldn’t effect GR though it’s fairly disputed whether it should be equal to zero and therefore if the measurements are accurate.
I do hope LISA can produce good data. I'm no physicist, but I have an intuative problem with dark matter, and am more comfortable with the idea gravitational effects persist in time, and this along with gravitational time dilatation effects could explain things like the dark matter plug number and uniform stellar radial velocity
Imagine a membrane-- but it's not like the one you're thinking of. It's enveloping everything-- and everything inside of any instance of a thing. And inside of its components, and their components, and so on. It can fold in on itself, around itself and anything else. That sounds a bit mad, but that's basically radio. Spacetime itself logically necessitates a memory in order for it(*or anything, actually) to persist. Figuring out how to forensics the universe is an entirely different problem though 😅
If such a sustained distortion persisted, it would keep spacetime curved without any visible matter, and the only term that could be given these dense regions of spacetime could be dark matter. Would be cool if we labelled ordinary matter and energy as memory, too, because that's what they actually are
That would be crazy if some galaxies that appear to have lots of dark matter like our Milky Way are actually just weirdly stretched from major gravitational events, while galaxies like NGC 1277 have completely avoided such events despite being nearly as old. Or maybe the fact that NGC 1277 lacking in recent star formation is the reason; spacetime there has long since recovered from the stretching that the Milky Way still experiences regularly?
Star trek TNG actually had an episode about how too fast warp speeds would damage the fabric of space time permanently. Curious if that turns out to be true. Regarding Einstein being right, do you have an answer to two parallel trains time synchronized along their lengths passing at zero distance that can query each other's time passage and must agree? seemingly voiding the no absolute speed premise of relativity.
I am confused... Isn't spacetime static by definition? It's space+time meaning time is already included in it, so how can it change? Don't you need time to happen for something to change? Maybe this is now some kind of terminology problem but I didn't understand this...
Honestly, this is way more sound than Dark Matter or Dark Energy. That spacetime itself gets formed, over billion of years, like clay and becomes shaped spacetime. The grinding of all the gravitational waves (any gravitational interaction leaves a mark) and forms the curve of localized spacetime. For example forming a halo well around galaxies, massive spacetime masses that move, makes absolute sense. I hope we can verify this memory effect. Or not, happy with both. Both give us more clues.
Hey PBS Space Time, I’ve had this idea for a while now. A theoretical field. Quantum fluctuations take time to annihilate. When created near the event horizon of a black hole, the pair falls toward it. It has a speed. This means there is a distance at which, if far enough, they have enough time to cancel before interacting with the event horizon. But within that distance, the pairs get a chance of being split. If one of the virtual particles touches the event horizon, the other is granted positive energy via quantum tunneling. This makes the one that touches negative and takes mass/energy from the black hole. The other one has to get emitted and that’s hawking radiation. It gets propelled outward in a line from the singularity the negative particle at the event horizon and itself. The amount of energy this takes is taken from the black hole as the negative particle. How does the black hole lose mass/energy? The negative particle cancels out with an equivalent amount of information from the black hole being projected onto the event horizon as 2D info. This cancels out and teleports the info via quantum entanglement to the escaping particle thus not losing info in the process of Hawking radiation. There would be 2 zones. The initial zone of all pairs that qualify for this interaction within a defined distance based on the Schwarzschild radius. And then a 2nd zone which would be very very small. The distance of how far the virtual particles were apart from one another at the moment the one touches the event horizon and the tunneling starts.
Therefor if you traced a particle of Hawking radiation back to the source it would get EXTREMELY close to the event horizon and then disappear. You wouldn’t see it go backward for that half second 10^-24 seconds to be precise traveling a distance of 10^-16 meters. You wouldn’t observe that because it happened backwards in time. Which is possible due to the Heisenberg uncertainty principle. What am I missing? I’ve watched all of your videos. All of them. Even the one that says not to think of these things as particles because they’re really waves and you had the awesome visuals on it. Even so, they’re still particles. And particles need logic classical thinking. No?
I guess I hadn't much thought about how the different forms of elasticity might apply to spacetime, lol. Thank you for another excellent video! God be with you out there, everybody. ✝️ :)
Man when I started watching I was still in college, now im 30 and Matts beard is going grey. Hope the show keeps going strong for at least another decade
10 years next year (that Matt presents it)
That's not enough
In some frames of reference, he already has!
@@paulmichaelfreedman8334 10 years already?! no freaking way!!
I've watched since the guy before Matt. I'm more a fan than you. My fan cred is immense.
Hi, gravitational wave physicist here. Small correction on how LISA's interferometry works. It doesn't actually work like a physical interferometer because the lasers would become too faint at such long distances to do it the normal way.
Instead, it basically times the distance a photon takes to go from one detector to the other in 1 direction, and then the interferometric pattern you would normally get is reconstructed through a technique called Time Delay Interferometry (TDI)! Sadly the data analysis for LISA is quite different from the previous ground-based detectors and everyone's slightly panicking about it
It is impressive to measure those distances with the required precision given all the gravitational influences by all the other planets (or better said: objects) in the solar system.
@@kallewirsch2263those influences happen gradually
Why would they panic about it?
Thanks for your input.
I love learning about space. Thank you for all that you do. I’m struggling to communicate an idea, but I’ll try my best: assuming a perspective parallel to a solar system’s migration through space, the celestial bodies orbiting the system would at times “lead” the star and at other times they would “trail” the star. From the described perspective, could this be solar systems behaving as waves? If so, this could have implications for observing other systems in space if we are close to the described perspective? One such implication is that the orbit of the planets would have an oscillating impact on the solar system’s gravitational signature. Planets would alter the signature, not unlike a wave.
I just wanna thank PBS Space Time for all the hard work and great videos they create. I didnt know any physics and now i have a deep understanding of how the universe works. You guys inspired me to learn physics. Thank you.
Please remember to shout us out when you accept a nobel prize for your theory of everything!
You don't know physics. These are all public release contents, specialized in making the public amazed. Don't be a fool. To know physics, you have to actually read.
@patentpendulum what indicates that this channel is the only research they've done? It could have been their jumping off point. More importantly, why are you such a rude thief of joy?
@@KashishKebab that's the point, don't make something a jumping off point by watching some UA-cam videos.
I LOVE this stuff. It stretches my brain… it’s so amazing
To Matt and the team at PBS Space-time, thank you for your years of dedication and service providing us (the general public) such an in depth and resourceful insight into quantum physics, astrophysics, and all that is space and time. I've been watching since the days of calculating what planet Mario is on to jump as high as he does. Since the previous host... You enrich my life and satisfy my intense curiosity of the universe we live in. I live for this. Thanks again, JT Gullickson. From Canada. Love and Peace
Yes, but can it remember the 21st night of September? Love was changin' the minds of pretenders while chasin' the clouds away...
Best comment😂
Earth, Wind & Fire Remembers
Listen for the bongo man
😅@@frtzkng
Permanent displacement in space-time suggests it’s not only elastic but also has a ‘plastic’ quality, behaving like a medium that can be permanently shaped. This also opens up the idea that space-time could have quantized properties, aligning it with quantum gravity ideas.
Or the ether is back ...
@@parthasarathyvenkatadri *kicks door down*
"I'm back, b*tches!"
We already believed spacetime is quantized independently of the reasons you provided. We have believed it for decades. Hence why there is a major search for a quantum theory of spacetime.
Nice, like that idea.
@@parthasarathyvenkatadri The ether has technically been back what with the Higgs field. Just different properties than the ether of the 1900s
I hope Matt never stops hosting
Friends call him "The Werewolf". I'm not sure why.
This has got to be his dream job. He sells it like it is.
I have seen 4 comments like this on this video...Is there something I don't know?
Thank you Matt and PBS Space Time for being a place (in space time) that always provides coverage and release from the chaos and uncertainty of the world right now… no matter how bleak things can feel it always seems a little less dire when put in the context of the cosmos. Please keep making your great content ✨
"The universe is very old, but it remembers." Why was this so ominous!? 🤣
Dark Matter is really the Universes Big Book of Grudges and it is just waiting for the perfect opportunity to get even.
Okay, spill it. What did you do to the universe? 🤨
And it holds grudge!
Perfectly normal paranoia.
Pepperidge Universe remembers.
I am 70 yrs old , I remember how as a child I was fascinated in my maths / physics lesson with "Simple Harmonic Motion" - the sine wave. I started my adult life as a geologist , but then I moved into IT, then Cyber security , it was through a lot of weed and simple harmonic motion , that shaped my life
My favorite wave to go with weed - sound waves!
perdix)
"Gravitational Spin Memory" sounds like the name of a late-90s techno/hiphop band.
You spin me right around. 💫🪐💫
Or some sci-fi technobabble to describe a super-advanced alien civilization's information storage system.
"You encode information one megabyte at a time on magnetic media? The Pak-Thak Interstellar Imperium perfected gravitational spin memory to store trillions of petabytes over one hundred thousand of your years ago."
Or a new feature on Memorex cassette tapes.
It's crazy that you're having this right now. I'm about to submit a paper. Thank you for everything. I will be sure to note all the helpful comments and wonderful teachings on BAO.
I've been looking forward to LISA since LIGO started detecting things. The precision of detecting the position of the spacecraft relative to the other two is astounding and got me thinking about something I first wondered about in my early teens, extremely-long baseline _optical_ telescopy. It's a relatively simple matter to take data from two radio telescopes on opposite sides of the Earth, do some calculations and, boom, you get the resolution of a radio telescope the size of the Earth (though with only the light-collecting ability of the area of the telescopes). You _should_ be able to do something similar with visible light, but because they're so much smaller than radio waves, you can't just collect the data and do calculations afterwards, the light has to be collected at a single location and it has to take the same amount of time to arrive. I think it's been done at smaller scales of single telescope installations, but even that's pretty difficult. I'm guessing atmospheric disturbances would make it pretty much impossible at more extreme distances. But what if there wasn't an atmosphere? You could do it on the Moon, though you'd be dealing with moon dust, and line of sight isn't all that big on the Moon anyway which would mean you'd need to add extra complexity in the form of mirrors to redirect the light over the horizon (and each one would have to be just as precisely configured as the telescopes themselves. Orbital telescopes would be best, but you'd have to be _extremely_ precise with positioning each member of the fleet relative to the detector so that the light-speed delay from each collector to the detector is exactly the same. But LISA shows that kind of precise positioning is actually possible. So imagine a small constellation of Hubbles in a polar orbit with only mirrors collecting and focusing light on a detector craft that would be orbiting perpendicular to the constellation (or maybe stuck in a Lagrange point). Orbiting them around Earth would probably be the easiest, but if we got them to orbit the sun instead, we might be able to get some _really_ high resolution imagery. I don't think we'd be able to resolve an Earth-sized planet any bigger than a single pixel, but maybe we'd get a few pixels of a Jupiter or Saturn-sized planet.
Ever since the imaging of the two black holes a few years ago. I always wondered why they couldn't do the same thing with the size of Earth's orbit around the Sun. That would be substantially higher resolution then just the size of the Earth
@@jasonharrison25 WIth radio waves, you don't even need to take the readings simultaneously, so you can get a 2 au baseline by pointing a radio telescope at an object 6 months apart. It's, unfortunately not possible to do in the visible spectrum (at least, not without using a black hole as one of your optical elements).
@@StarkRG
Sure about not needing to be simultaneous? It is my understanding that when they took the measurements for the black hole images, they added very precise time marks (using atomic clocks) in order to correctly interfere the recorded signals in the computer. For interferometry you need 2 measurements of the same signal at the same time. You can not just take 2 measurements in time, let them interfere and hope for something useful.
There are two ways of achieving what you suggest here, optical VLBI it would be called I guess, and those ways explain why it has not been done before even though as you point out it is clearly a great idea.
The first is to reflect back the light collected from "light capture" spacecraft towards a single "detector" spacecraft, as you suggest. This means you can measure all the light in a single location with a single "time-base", essentially the photons are all counted using the same stopwatch, so there is no question of is we are talking about the same moment in time or not. This has the obvious issue that as the capture spacecraft are placed further and further away from the detector spacecraft, diffraction effects in the optical spectrum will mean they would need to be massive. Like... really massive. Like, kilometers wide massive, each... This is highly impractical and is essentially a non-starter (at our current Kardashev scale :)).
The second way is something that LISA does actually use itself, another thing you correctly picked up on. It is also done in many other experimental missions and is a rather new technique, still in its infancy (something I've worked on and still work on), and that is the idea of "optical time-transfer". This is, basically, time syncing using lasers ;). This means that you could have a whole bunch of "hubbles" with laser links between them, that essentially keeps their clock, and hence their photon counting "stopwatches" synchronised. Then the data recorded by each one can be resynchronised on the ground to form the interferometric image. This is much easier said than done of course, but the current state of the art here is limited by the clocks used themselves. The best clocks we have ever built (which can't really go to space... yet, I know the people making them and they will try :)), are still not good enough for visible spectrum interferometry, at least not without significant correction systems of which LISA will indeed be pioneering, but not anywhere near the level needed... Anyway, it seems this is the way to do it, and work is ongoing, so watch this space I guess.
So Dr. Serova was right and regular deformation due to FTL propulsion causes cumulative damage. Better limit cruising speeds to warp 5 until we can come up with variable geometry warp fields that will be able to prevent further damage.
exactly. soon spaceflight will become bumpy. quite like in the old flash gordon movies. they'll tell you to keep your seat belt fastened at all times.
@@newerstillimproved ?
@zhavlan1258 these 2 havin a quick joke, don't worry about it.
SpaceTime is the greatest thing on UA-cam and Matt is a national treasure for us Aussies. This episode was fascinating!
3:00 This is not strictly true: water waves create Stokes' drift, which is a net displacement of water in the direction of the wave.
Whoa. Just at the surface, yeah?
It's also not true for electricity. Electron drift velocity is a thing.
@@doublepinger It's also not true for Mexican waves. At higher energy levels, fans have known to end up several seats away.
@@MrAntipaganda It tails off with depth en.wikipedia.org/wiki/Stokes_drift
@bananabourbonaenima I think that doesn't matter as much here because we are only concerned with surface effects since the surface of the water is like a 2D analogy of 3D space.
Made me sit up! I thought Matt said, "Thank you Raytheon for supporting PBS".
That's an interesting development I thought.
Ah! Raycon! (mental note to get ears checked)
Listen if Raytheon will keep PBS fighting against misinformation and conspiracies then let’s goooo
Raytheon did sponsor PBS Nova
We will shoot missiles at a neutron star
Fancy space rocket is just one component away from being fancy space missile!
@@ProbablyNotAChickenwhy does this read in a Russian accent to me 😂
Absolutely love Space Time, always comes with super creative graphics, vids that helps people like me see what's being discussed in my mind's eye. Keep up the amazing work Matt and the team
I first learned about memory effects in spacetime in the Star Trek episode "Force of Nature" :D
A classic episode
Interesting. I'm a fantasy author, and space-time is an element in my magic system. The memory of spacetime gives me an idea for a Mind+Space (the two are seen as opposite elements, so this would be a very OP ability) spell that allows the caster to read the "memory" of the space around them to see past and current events at great distances.
I love when science gives me an idea.
Always a great moment on Thursday when PBS Space Time uploads a video
I would love to hear an engineering analysis of LISA. Especially the relationship between orbit, mass vs. sensitivity and resolution. What limits the orbits to where they are going to be? Can it be upgraded by adding more satellites? What exactly gets upgraded? What happens when the satellites get more massive?
It's fun to think about the elasticity of space time! Good episode!
Thank you Matt and PBS Space Time crew for another great video!
A black hole is by definition a memory of spacetime since the matter that created it is no longer there. There is nothing there, no matter, only the singularity. Thus - a memory.
This is super interesting, I have never heard of gravitational memory before.
Question: Where do gravitational waves "go"? Like do they chircle around the Universe? When you have a wave of water it ends up as energy that is transfered to the shore. Where do these waves (since they are form of energy) ultimately end? They can't propagate through the universe forever?
there is a similiar question on physics StackExchange. and the answer is pretty good. in a nutshell, they can loose energy to heating up matter, but mainly they get distributed soo thin and get redshifted so much that they don't have any effect anymore. like light
One idea I've heard for the explanation of dark matter is that black holes might leave a small, permanent kink in spacetime after they evaporate. Neat idea.
There is no evidence that a black hole has ever evaporated. The universe isnt old enough for that.
I just posted a similar comment. It’s an interesting idea to think about
Without seeing any math on it that seems unlikely; there would have to have been a *lot* of black holes for their remains to account for 27% of the mass of the universe...
But doesn’t it take googols of years for Hawking Radiation to evaporate a black hole entirely?
Don't think black holes have begun to evaporate yet... it will start in like a gagillion years.
Only 4ish minutes into the video, but my new hypothesis: could the constant addition of memory by the equally constant events producing waves, be stretching the fabric of space-time itself, and therefore be at least partially responsible for the expanding nature of the universe?
Fascinating stuff.
My thoughts as well.
Memory adding information and therefore causing expansion :o
This is why they set a limit on warp speed in star trek. Stretching the space ahead and behind you makes it wrinkly and even saggy which disrupts navigation. Its one of the hazards of old age
My memory foam forgot...
I was born for this, how many years until we replace time with memory
Last time I was this early the electroweak force hadn't split yet
Thank you for doing this topic. I read an article about gravity with no mass and i didn't really understand. When i finished it i thought....i hope SpaceTime does a video on this.
Thanks again for great content.
I can't wait to buy a few Penrose Diagram Glasses !!
I love binge watching all 10 seasons. Thanks!
im a big fan of the term "giant space laser triangle"
Let's gooooo! We love PBS Space Time, thank you so much for partnering with us and keep it up with the incredible videos 💙🎧
There's your warp-drive signature right there. Just sayin' - that sounds like a fairly plausible explanation for the, yet to be non-fiction, warp-drive signatures that all the Star Trek crews were so keen on using to follow some rogue ship after it ditched them.
I’m so glad I fell in love with science before the world went insane. I have all I need in the reassurance of empirical research and observations. 🦋✨
Expected a mention of the pulsar array gravitational observatory, but I guess it detects much longer waves than the memory effects.
Was just watching a TOE episode about how quantum mechanics can be written as a classical nonmarkovian stochastic process. Pretty neat that there are actual memory effects in gr
That was an excellent interview. My head is still attempting to unravel some parts of it lol
>
Back to this gravitational memory idea. The implications of that are also quite profound.
The concept of space time not being elastic and not returning to a previous equilibrium after gravity effect has passed is difficult to imagine.
For example as an extreme thought experiment, if a Black hole evaporated does the space-time around where it was remain stretched/warped?
Pepperidge Farm remembers
I used to be irritated by meme comments, but then I spent the night at a Holiday Inn.
Lol
....and there it is!
We must all continue to grow.
Good job figuring out the scienc-y part of my upcoming time travel novel. Man, you're always that one step ahead of me 😅
Yes, gravity, and apparently warp engines can leave permanent marks on space time. That’s why you can’t travel faster than warp seven through the same region of space too many times in a row. I most of us have already seen that episode of The Next Generation.
I swear to god , I thought that also. I was going to make a similar comment , decided to scroll down and see if some one beat me to it ! Hats off to you !
Fascinating. I imagine the effects it could have on time!
I may not be able to wrap my primitive brain around many of these concepts, but they're so fascinating & important to humanity that I'll always support you guys!
Yet another excellent video! And I love the music track - sounds like an ambient track for a stealth level in a 2000s game. Would be awesome to know the artist and the name of the track. It was surprising to not see this aspect of the video being mentioned in the credits.
Yeah, my car remembers its physical interactions with other traffic too. The fact that even empty space can be dented is depressing in so many ways.
Every time i see a post from this channel im like yeah, i gotta close the windows, lock the doors and sit in front of the tv some from of hydration.
6:15 this animation always looks to me like a Neptune-sized triangular spaceship chasing earth
You see, we are starting a project in which we play pacman in space using earth as the player and those satelites are the first 3 lines of drawing a Neptune sized ghost 😂
O.O
Both very informative, and quite aggressive.
The most threatening educational line I've ever received.
"The universe's old, and it remembers"
Guys. You _have_ to talk with whoever is titling the videos. Every time the video is about spacetime, the thumbnail says “spacetime” but the title says “Space Time” (when referring to the science thing, not the show).
We know that speeds above warp 5 permanently damage the fabric of spacetime, unless that is if you dramatically fold up your nacelles before each use.
I'm reminded of that episode of Star Trek TNG where they discover that using the warp drive is causing gradual damage to the fabric of space-time.
love you, love this. private sector could deliver this. not to mention this is ad-sponsored now.
This is the basis for Alastair Reynolds' FTL comms called Galactic Final Memory in his book Chasm City, part of his Revelation Space series. Couldn't recommend those books enough
That series starts so well but ends so bad.
I'm not sure if _space time_ can remember, but I know 100% for sure that Pepperidge Farm remembers.
Love your work, want to see more -SO GET WELL SOON!
If we could have greater accuracy with measurements (more watts/higher frequencies needed probably) we could use singularities as a gravitational lens to probe even "deeper".
Due to the inaccuracies and limitations in the present day mathematics, things like "beginning of the universe", infinite curvature/density or "no spacetime beyond singularity" are most likely glitches and misinterpretations caused by the inaccuracy. Imagine trying to record 20kHz signal with a microphone having a 100Hz max sample rate. Yeah. You'll get artifacts and glitches.
So no Lawrence Krauss, virtual particles do not "come out from nothing" and neither does the universe "come from nothing" : ) Just because our maths and methods are not absolute and perfect, doesn't mean we should reflect our limitations to what we assume or interpret about reality.
What I don't understand is how LISA can maintain relative position accurately enough to then be able to detect the change from the gravitational waves.
I always thought that the assumption that spacetime is Euclidean at some distance from mass is ripe for questioning. Even a small curvature caused by mass passing by, over a large enough volume, would look like additional mass.
Isn’t it thought that average curvature is negative, as in de Sitter space?
This is really exciting! This would rule out a lot of dark matter and dark energy theories!
it would be nice to do a similar video for the other fundamental forces
Super professional and informative video, as always!
The only cogent and relevant comment I can make about this video is that this is the best that Matt's hair has looked in any Space Time video I've seen. Keep growing it out Matt!
another PBSST banger
The universe is a state based machine. The arrow of time couldn't exist without 'memory'.
To me it sounds like the memory is in the objects occupying spacetime, not in spacetime itself.
Just like ramping up your sound system to max volume. After turning it back down it still plays the exact same music, but you'll hear it differently because of hearing damage.
9:00 You know what is funnier than a system of non-separable PDE? A system of non-separable non-linear PDE!
❤Thank you very much for this helpful lesson Matt
If these 'displacement memory effects' can be measured by a free-floating system with arms long enough to detect low-frequency signals, why can't they be measured by the same Pulsar Timing Array (PTA) we used to identify the gravitational wave background?
Because the star's motions aren't well controlled. The result of a wave's passage will be a shift in position of the pulsars, but those happen all the time. To measure ,it you need a more precisely controlled arrangement.
That was beautifully poetic
Very informative, thank you for all good job all you guys do! 🎉
PBS space time remembers
6:41 it detects mergers BIGGER than LIGO? I'd have expected from having 10^5 more baseline it would detect far SMALLER events??
This is not only good stuff, but crucial. At last we have a plausible way to confirm how the gravitational metric of space time might actually change after a major gravitational event. Not only should this validate GR, but also may shed light on the effects we characterise as dark energy and dark matter. Fingers crossed that we now have 'game on'.
Ah a Triangle so close to my heart!
When measured, the curvature component of the Freidmann equation is equal to zero so it shouldn’t effect GR though it’s fairly disputed whether it should be equal to zero and therefore if the measurements are accurate.
I do hope LISA can produce good data. I'm no physicist, but I have an intuative problem with dark matter, and am more comfortable with the idea gravitational effects persist in time, and this along with gravitational time dilatation effects could explain things like the dark matter plug number and uniform stellar radial velocity
Fascinating concept!
Imagine a membrane-- but it's not like the one you're thinking of. It's enveloping everything-- and everything inside of any instance of a thing. And inside of its components, and their components, and so on. It can fold in on itself, around itself and anything else.
That sounds a bit mad, but that's basically radio.
Spacetime itself logically necessitates a memory in order for it(*or anything, actually) to persist. Figuring out how to forensics the universe is an entirely different problem though 😅
Well, I don’t know about that but I will always remember what time and space did to me!
Fascinating.
If such a sustained distortion persisted, it would keep spacetime curved without any visible matter, and the only term that could be given these dense regions of spacetime could be dark matter.
Would be cool if we labelled ordinary matter and energy as memory, too, because that's what they actually are
That would be crazy if some galaxies that appear to have lots of dark matter like our Milky Way are actually just weirdly stretched from major gravitational events, while galaxies like NGC 1277 have completely avoided such events despite being nearly as old. Or maybe the fact that NGC 1277 lacking in recent star formation is the reason; spacetime there has long since recovered from the stretching that the Milky Way still experiences regularly?
Pepperidge Farm remembers.
Star trek TNG actually had an episode about how too fast warp speeds would damage the fabric of space time permanently. Curious if that turns out to be true.
Regarding Einstein being right, do you have an answer to two parallel trains time synchronized along their lengths passing at zero distance that can query each other's time passage and must agree? seemingly voiding the no absolute speed premise of relativity.
Excellent video 📽️ 💯
Keep up the excellent work!
Ahhhh always love to hear Soft Gold by Frederic Mauric Fortuny
It's always good to give engineers something to do. Otherwise they get into trouble.
At 2:30 I am reminded of Akira
Akira toriyoma 😮😮😮
The memory of the universe is probably much, much richer than Physicist can expect.
I am confused... Isn't spacetime static by definition? It's space+time meaning time is already included in it, so how can it change? Don't you need time to happen for something to change? Maybe this is now some kind of terminology problem but I didn't understand this...
Honestly, this is way more sound than Dark Matter or Dark Energy.
That spacetime itself gets formed, over billion of years, like clay and becomes shaped spacetime. The grinding of all the gravitational waves (any gravitational interaction leaves a mark) and forms the curve of localized spacetime. For example forming a halo well around galaxies, massive spacetime masses that move, makes absolute sense.
I hope we can verify this memory effect. Or not, happy with both. Both give us more clues.
Hey PBS Space Time,
I’ve had this idea for a while now. A theoretical field. Quantum fluctuations take time to annihilate. When created near the event horizon of a black hole, the pair falls toward it. It has a speed. This means there is a distance at which, if far enough, they have enough time to cancel before interacting with the event horizon.
But within that distance, the pairs get a chance of being split. If one of the virtual particles touches the event horizon, the other is granted positive energy via quantum tunneling. This makes the one that touches negative and takes mass/energy from the black hole. The other one has to get emitted and that’s hawking radiation.
It gets propelled outward in a line from the singularity the negative particle at the event horizon and itself. The amount of energy this takes is taken from the black hole as the negative particle. How does the black hole lose mass/energy? The negative particle cancels out with an equivalent amount of information from the black hole being projected onto the event horizon as 2D info. This cancels out and teleports the info via quantum entanglement to the escaping particle thus not losing info in the process of Hawking radiation.
There would be 2 zones. The initial zone of all pairs that qualify for this interaction within a defined distance based on the Schwarzschild radius. And then a 2nd zone which would be very very small. The distance of how far the virtual particles were apart from one another at the moment the one touches the event horizon and the tunneling starts.
Therefor if you traced a particle of Hawking radiation back to the source it would get EXTREMELY close to the event horizon and then disappear. You wouldn’t see it go backward for that half second 10^-24 seconds to be precise traveling a distance of 10^-16 meters. You wouldn’t observe that because it happened backwards in time. Which is possible due to the Heisenberg uncertainty principle.
What am I missing? I’ve watched all of your videos. All of them. Even the one that says not to think of these things as particles because they’re really waves and you had the awesome visuals on it. Even so, they’re still particles. And particles need logic classical thinking. No?
"Gravity" is the magnetic buoyancy and the density of the universe 🌌
I guess I hadn't much thought about how the different forms of elasticity might apply to spacetime, lol. Thank you for another excellent video!
God be with you out there, everybody. ✝️ :)
Pnut and Fred will be remembered.