Is The Universe Finite?
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- Опубліковано 1 гру 2019
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The universe is big, really, really big. Although according to a new paper, it may literally be infinitely smaller than we previously thought.
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Written by Matt O'Dowd
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Every time you walk out the door, light from the Big Bang strikes your face, enters your eyes. This is the cosmic microwave background radiation - the left-over heat-glow from the very early universe. We can’t see this microwave light with our eyes, but we can catch it with even a simple radio antenna. As soon as we became aware of its existence we’ve been feverishly building better and better devices to collect it. Why? Because it encodes so many secrets. And within this light, a group of scientists have just found evidence of the limits of space. A clue that our universe may be actually be finite in size. Today on Space Time Journal Club we’ll delve into the Nature Astronomy paper that just reported this: Planck evidence for a closed Universe and a possible crisis for cosmology by Eleonora Di Valentino, Alessandro Melchiorri, and Joe Silk.
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and thus the war between the flat universers and the curved universers began
meta
Don't let the flat earth guys see this ..
I tend to the side with the best data
@@hakmanp.8702 Yeah the flatards will probably confuse everything they hear...I can already hear them now, "Scientists said the universe is flat, thus the Earth is flat!"
@@big-ounce I like how you took this joke seriously lol
"the universe will expand forever, unless we were mistaken"
Perfect description of physics
You got it!! Theories are deemed to be correct until observations do not match the theory. Then scientists either stop using it or continue to use it because it fits the data from other types of observations. Theories are a set of hypotheses used to construct a mathematical model of all the data from all known observations of all relevant parameters of the physical universe.
If the initial assumptions used in this process are incorrect the model will fail to make good predictions. Another outcome can be the predictions well work for some observations but not for others. This indicates the theory is incomplete or assumptions of how the universe works are.
😂☝️
So true. I highly doubt the universe is actually infinite, physics goes wonky when the word infinite is used. The simple question of "what would the density be if I spread the atoms of this apple across the universe" becomes infinite as a fraction of infinite is still infinite. It's finite but expanding faster then light and thus is effectively infinite to us observers. The actual size of the current universe is impossible to know, just like what was going on before the universe expanded. We can make grand and complicated sounded guess, that are still guess's and only slightly more logical then a giant turtle carrying the universe around on it's back.
@@palladin9479
> The simple question of "what would the density be if I spread the atoms of this apple across the universe" becomes infinite as a fraction of infinite is still infinite.
not necessarily. with calculus we can ask what is the _limit_ as the distance between each atom of the apple approaches infinity. as we stretch out our apple, the density gets lower and lower, approaching 0. so, we can say that the density in the limit (where each atom of the apple is infinitely far away from eachother) _is_ 0 (which should make intuitive sense).
I _want_ an infinite universe. A spatially finite universe could still be meaningfully infinite in time, for example under Penrose's eternally expanding Conformal Cyclic Cosmology model (in which expansion eventually causes scale to lose all meaning, and the expanded universe becomes indistinguishable from the big bang singularity, repeating the process). But really I want a universe that is infinite both in space _and_ in time. This is the reality I'd be most happy with. So, you know, make sure your scientific findings conform to my desires, please.
isn't this covered in another episode?
@kevin this will make you a popular cosmologist, but a bad scientist. The big question. Is all this guess work really physics? It is more science fiction than science.
@@thewizzard3150 true
God: *invents confirmation bias*
There, fixed it for ya
@@pureevilecho150 and by confirmation bias you mean the universe is biased to confirm what I want right?
Since we have discovered that gravitational waves travel at the speed of light, this implies that the universe might be made up of all three geometries, depending on the mass of each section. As space expands, portions of it become causally disconnected as the rate of expansion from any given point becomes superluminal. Therefore, as matter passes beyond this event horizon, its mass effectively leaves the universre, and, that means the universe could, theoretically transition from positive curvature to negative curvature.
"...and, that means the universe could, theoretically transition from positive curvature to negative curvature." An amusing side issue, I'm a Heretic. The net energy value of the Universe is always 1. I love gravity waves travelling at the speed of light. Baryonic Matter isn't even 1%. That alone, tells me alot.
imagine if the universe being curved gets proven to be true and 100 years later Flat Versers will be a thing and worse yet is they would have little way of proving the other case
No, but if you look at an encyclopeedeeya from 61 years ago it shows proof that someone said something like there's a thunder dome 13000 parsecs above the southern-most sector of the universe and the governt-ment is hiding eeliums! Therefor: eeliums. *cough* I mean flat universe.
Summing up a flat earther for reference; hops in spaceship, goes into orbit, looks out window 'nah, this is fake, you're tricking me, how do I know this isn't a fake rocket, why don't you open a window and prove it'.
Fuck flat earthers.
@Danny Meeks ;o
@Danny Meeks well..figures.. flat earth
*1000 years. We've known the Earth round for 1000 years.
“Is the universe infinite?”
“No”
“Could you check?”
“No”
Do you think you're being funny, or are you just an idiot?
“Is the universe infinite?”
“No”
“Could you check?”
"No need. If the universe was infinite, there'd be no space."
EOM
@@Mick0722MX
"is the universe infinite?"
"Yes"
"Could you check?"
"No need. If the universe wasn't infinte, dog farts would've had a smell of strawberries"
^same level of argument, of what you wrote there.
@@dushas9871 You're a moron. The universe is finite. If it wasn't, there would be no space. Good luck, dipshit.
You doofuses, it's a Spongebob reference
@@Mick0722MX watch out we have a badass round universer out here
It's so cool how he always creatively manages to finish with the phrase spacetime. Good, deep episode.
It's only when you consider how much we don't know that you get really can hold the universe in awe.
It's only consider you when get we know in don't much universe you hold really can in awe.
@VeroMithril What are you talking about? Religion and spiritualism often talk about not knowing it all.
@VeroMithril And that is also a principal in science even though a lot of scientists think they do know it all.
@VeroMithril You see that's your problem. You read one book and you think all religions are the same. Educate yourself on the various religions first then come back to me.
A lot of scientist and so called "UA-cam scientist" think they know everything while claiming they know little at the same time. Just like you.
@VeroMithril And that's why you'll never learn anything. Because anyone with eyes can read what I said and not find anything about me discrediting science but of course you made it up.
But since you have very limited reading ability I'll reiterate it for you. Scientists think they know everything. There is nothing wrong with science itself. So go ahead and twist what I said again so it can suite your beliefs. You are just some random guy on the web who's existence means nothing to me so why would I care if you block me or not?
I'm just correcting your ignorance so future people can benefit from it.
Can I just say I'm so grateful for PBS and this program and Matt? As a layman and as someone who never attended higher learning, I don't pretend to understand everything (or even most) of what is discussed, but physics in general fascinates me, and I'm so happy about the style of presentation. Matt talks like a calm and rationale adult, and treats us with the expectation that the audience doesn't need to be coddled or titillated with a pandering tone or memes bombarding the video. In a world where a lot of "educational" content almost seems to have contempt for its audience, Matt and Spacetime makes me feel respected, and for that I can only give the same respect right back. Thank you, please keep doing what you're doing. You are so appreciated!
Preach! Thanks for this thought out and completely correct comment, I couldn't agree more 💯🔥
@@matthewreynolds8068 Thanks. It drives me crazy when YT recommends some channel or video and the content creator sounds like When Animals Attack!
@@leerv. 😂 You said "sounds like 'When Animals Attack'"😂 edit: I just had to reply when I realized you are right. Lots of education channels here on UA-cam almost have a condescending, "I'm explaining this to a 5 year old" kind of tone that makes me happy for all the 5 year olds. PBS Spacetime inspires me to dive headfirst into the maths (even though I just finished precalculus and am in way over my head with field equations) and research the names and topics covered in the video. Plus Matt's soothing accent and demeanor definitely helps
@@matthewreynolds8068 Absolutely. I can hear them in my head. "If you FELL.... into NEPTUNE... you'd probably DIE." I'm on my fourth decade, not my first, please don't talk to me like that. You know? :P
Congratulations on the research! I'm horrendous with math. If I can't get a holistic/intuitive grasp of the astro/physics concept being discussed, I'm lost.
No, you may not.
It is mind blowing to me that they can actually compensate for such much gravitational lensing at all. I mean, that has got to be a LOT of work.
put it on half speed and it's like you've just run into him at a bar and struck up a conversation
Hahahaha
I'd love to have a drunken / stoned conversation with him
Half speed, would that double infinity?
Questions I've had since I was just a boy:
-What was the first thing created? What created it? What or who created the creator of the first thing? Is it possible at all to have a first thing created?
-What is outside of the universe? What is outside of the things that are outside of our universe? What is outside that too?
Really ? This a serious science channel and if you're going to come here and ask such childish questions then we might as well give up and .......oh ! wait you're right .....
@@elizabethwinsor5140 :D :D
I LOVE PBS SPACETIME!!. I just wanted to say thanks for everything you guys do. I've been a follower for years now and I have seen every video multiple times. Keep it up PBS SPACETIME. Thanks for producing these videos and making them an essential part of my perception of... Spacetime :P
You made me smile, have a great day!
Yup, it's insane how much knowledge I've gained off UA-cam from channels like this. The best thing to come out of my computer addiction from childhood
Arvin Ash and MindScape are good too.
👏🏻 👏🏻
Some of them get super heady for me, and I just nod along to the equations, but I totally echo your sentiment 😸
My problem with all this size/shape of the Universe stuff is that we can only see a tiny part of it - and what we can see right now is already billions of years out of date. For all we know, space civil engineers could have knocked down the entire Universe several light years away and built a car park around us and we won't even know about it for years.
Yea, but we'd be able to tell them how far of from 'level' their park is based on the curvature of the space-time it's built in. And mocking engineers for imperfections in their designs is good enough for me.
Bruuh🤣😂🤣
Yes but this is just something we have to accept when observing space, we will always see things long after they happen cuz the speed of causality
Buh... We can see the big bang.
Also, we can see proto-galaxies.
i still subscribe to the simulated universe theory. i think data is densest around earth (or whatever set of celestial bodies are being actively simulated) and sparser the further you go from it. since there would be no meaning to make data that is inaccessible from where we are, there just... isn't.
A lot of people seem to be asking if the universe can change shape due to the ever faster expansion increases over-time. Like one that started off as a closed sphere, currently opening up to be flat, and then gets inverted to become whatever 4D-pringle-saddle-hypershape the negative curve was supposed to be
I like how they took the time to deviate to explain everything you need to know to understand the conversation. While saying the universe curves in on itself is easy to visualize, it's hard to understand the universe mathematically without delving into some difficult geometry first! Amazing visuals that make it super simple to understand such a mind-shattering revelation of a finite universe!
Can the Universe transition between different geometries?
Start off closed, then get more and more towards flatness and then 'invert' into negative curvature?
And then it turns in on itself and eats itself and is once again reborn.
Perhaps, at this stage, anything is possible.
@@elias_xp95 There is a theory about this actually, it says that the universe might expand so much that the forces will colapse (like if we were going backwards in time) then producing another big bang. As far as we know this could be x number of times that this has already happened
I would assume there’s some form of conservation as that would require it to expand infinitely instantaneously and then shrink infinity instantaneously
If a flat infinite universe curves into a closed finite universe, what happens to the infinite matter/energy in the infinite space?
If dark energy density isn't constant
I love how every episode ends with ".…. of Spacetime."
And you can tell when Matt is about to finish because his firehose delivery slows down as he moves his closing proposition to end with that phrase.
The "of" is not always there, for example in one of the episodes he ended with "our ever-expanding... spacetime".
@@gabor6259 he had a bug in his system memory that day. Won't happen again. He improves with time.
@@dodid0 You mean he improves with... spacetime.
wtf dude spoilers arent cool
If the universe is curved/round. *That means there has to be a center of the universe.* what could be at the center of the universe?
That center would not be inside the universe, of course, just like the center of a sphere is not on its surface.
@@thomaskoller8282 still very intresting thought. Would that be where the big bang started? I know the center wouldn't be like the core of a planet.
So if the universe is sphererical or round. Then there has to be a center?
I don't know much about this. But logically speaking. *If* the universe is curved or round than must be logically a center.
@@thomaskoller8282 that's very interesting, I hope he talks about this
@@tyler5914 every point is at the center (like a dot on the surface of a sphere would be)
Extra like 👍 for the “Hitchhiker’s Guide to the Galaxy” reference 😅 “Don’t Panic” and know where your towel is ✌️
OI if you give 2 likes they cancel each other out
Professionals in every other field: "Omg, our models are not correct, we are screwed!"
Physicists: "Awesome, all we know might be wrong, more fun stuff to think about!!"
Call it ... job security
Also physicists: sadly, we were probably right.
Too bad climate scientists aren't so open minded. They say their science is settled. They say anyone who doesn't agree is funded by fossil fuel companies or just stupid.
@@JoeZorzin
What would you say if a flatearther said you are not open minded?
@@omeke9336 I blew my mind in the '60s, so it's totally open.
Just got out of school, literally learned more right now than in the seven hours past.
Actually, I enjoy watching a good Numberphile or Arvin Ash video.
You didn't learn more from this vid than you did in the past several hours. Watching this vid has taught you something that you aren't learning in school at all, and the brain processes new data with greater emotion. This vid didn't tell you how to calculate the curvature of space, and you haven't even read the paper that the vid is based on 😑. Don't forsake what you're learning in school now.
Btw all this stuff, even Numberphile's content, vsauce, veritasium, etc are college level stuff, which means if you want access to the treasure trove of info that they're using to make their vids, then buy college level textbooks. You'll literally learn more than what you're getting from the content creators.
Don't let school get in the way of education.
@BBB H I wasn't replying to you. But anyways, when I say the brain processes new information with greater emotion, I mean seeing or experiencing something absolutely new floods your brain with hormones like dopamine, and adrenaline. It's partly why people feel good when they buy something new. Partly why you are amazed/disgusted at a new sight. Partly why you feel a thrill during an eureka moment.
OP has an interest in astronomy, and seeing new information about astronomy, especially considering this isn't what he/she typically learns at school causes op to feel he/she has learned a lot, when it's really just an emotional response to what he/she is experiencing.
The topics that channels like veritasium and numberphile address are indeed college level, but their appeal is that they simplify the information to make it accessible to more people. After watching vids by veritasium, a highschooler might say "this is amazing! Why haven't I been taught this?", while someone in college might say "oh, I learned all of that last semester." This is of course dependent on what you're studying btw.
@tommy aronson
OK, boomer!
Thank you so much for uploading this video. It is helping me get through the pandemic!
I have been out of the university world for 40 years now and and I am amazed how much has changed in our understanding of cosmology and physics during these years. I think it is important to realize that it is not possible to gain a deeper understanding in stuff like this without studying the underlying math and science. This is probably the reason behind all the crackpot theories not worth wasting Your time on. On the other hand I would have been infinitely thankful for videos like this as motivation when studying abstract subjects like quantum physics etc. The attitude at the time was very much do the math first and refrain from applications until mathematical maturity was achieved. It is like reading a book, very valuable to get an overview first before diving into details and to have some clue why. Like all the discussions about the twin paradox easily debunked here when we know in detail how the Lorentz transforms work...
Your idea of a donut shaped universe is intriguing, Homer. I may have to steal it.
- Stephen Hawking, 2016
@Simon Read while kidnapping himself 🤣
@The Illegitimate President Agreed. It should be obvious to anyone, that it's shaped like a pretzel.
@The Illegitimate President Toroidal things occur all the time.
No biggie. It's just another type of sphere.
But the curvature would be fatter in one direction than another. There's no evidence for that (currently).
Plus 🍩 aren't good for you.
*starts talking about blobs*
“I’m somewhat of a scientist myself.”
I like your username lol
fynes leigh very though provoking, I appreciate the insight :)
@fynes leigh I'm constantly aware of my dreaming; many times I realise that I'm dreaming but continue the dream and watch my participation in it. Particularly during this time of the virus, my dreams are much more interesting than my life; that doesn't include input from PBS, books, etc. Oh, I do have a question: Wouldn't the 'dark energy' increase as the volume of space increased. I may have missed it, but I haven't seen that addressed in the popular science I've read or watched.
@fynes leigh I understand what they mean by 'dark energy', but my understanding is limited by not being able to do the math. I'm rarely aware that I'm dreaming; that would ruin the fun, I'd think. I can usually figure-out the reason for a particular dream, like trying to work-out things which happen during the day, my subconscious trying to make sense of the daily goings-on. Many of them involve my trying to explain myself to others during my dream. What I'm thinking when I fall asleep has nothing to do with what I end-up dreaming, unfortunately. I'm going to study your comment some more and I'll continue. cheers
WOW!
Love this channel and the host. Watching these vids made me change my major to theoretical physicist.
Thanks Matt of Earth, as of always, I appreciate your work always all ways CMB
It'd be nice if the universe was a hyper-torus. Then parallel lines would stay parallel, even while the universe is finite.
@fynes leigh - So you correctly identified my comment as a joke, but attempt to address it seriously? Fine, I'll play.
You can ascertain that the earth is a sphere (roughly) without leaving its surface. A hypertoroid is also a finite shape, and so this could potentially be measured from within the universe. A hypertoroid is even in keeping with current observation inasmuch as parallel lines don't intersect as best we can measure.
The Hard Problem that clap back though 😂😂😂
fynes leigh You’ve got some deep issues going on. Who hurt you?
There might be more than one universe. Don't fall into that semantic trap. Remember the ministry of peace refers to the war department.
The universe simply refers to any spot we could in theory explore in normal 3d space.
fynes leigh you seem to be someone who hasn’t the faintest idea of good grammar.
Lord Kelvin : “There is nothing new to be discovered in physics now.”
Physics : “hold my ......”
I doubt that's historically accurate. Lord Kelvin taught a master class on what he called the "dark clouds" over physics of the late 1800s, which included radioactivity, the ultraviolet catastrophe, and the photoelectric effect.
Quantum mechanics?!
@@nirbhaygurjar7015 In the long run everything is physics. Physics all the way down.
@@daedalus-7 I have no idea where you got that from. But I learned this bit of history from "The Quantum Revolution: A Historical Perspective" by Kent A. Peacock, a book I picked up from my university library, definitely reliable. In any case, assuming what you say is correct, he was simply not being himself in his later years. People can and do become senile.
hold my physics
If expansion rates can effect the curviture of the universe then could it be possible to change from positive to negative curviture? Would this mean tearing apart an edge of the hypersphere?
My high school math professor was occasionally saying something along these lines: "Parallel lines meet or diverge somewhere in the infinity of the universe." now this makes much more sense :D
Then they are not parallel lines by defintion
@@roberts8524 Nothing is precise enough to be infinitely precise .
3:16 Isn't that technically a 2-D projection of a 3-D projection of a 4-D hypersphere.
In your 1-D brain.
@@adityasaklani8710 oof, I guess that you're right.
@@randomguy263 Have you heard of our lord and savior 0-d consciousness?
It is a attempt to do so, which is incorrect. A 3d sphere has the property that its surface is contiguous at all points, the 2d projection mapping here is not even close and is only half the sphere. let alone a 4d mapping. 2d is rectangular by nature, mathematically as well.
@@SomeGuy-nr9id are you basing that off of the 3d coordinate system? If so then you should look into polar coordinates.
11:00 Dark energy is an evil super flower, I knew it!
Global Digital Direct Subsidiarity Democracy . Most likely the bunch that Adam gave to Eve on their first date. Big mistake.
Undertale's flowy confirmed
"Feed me, Seymour, and you might just learn the secret to the entire universe."
"world war 3 will be fought with flowers"
-Einstein
The flowers look to be a species of cosmos - maybe Cosmos bipinnatus daydream.
Nice touch.
I’ve always said I think the Universe is pretty big. How big exactly, I don’t know, but definitely large. I’ve been saying that for a while and don’t see myself changing my mind anytime soon.
It still boggles the mind that the universe is expanding at the speed of light *and its accelerating*. That makes about as much sense as magnets.
The trick is that while traveling "through space" is limited to light speed, there is no issue in relativity with space itself moving faster than light
I'll forever be thankful to this channel and the people behind it, i could honestly watch all these videos in a row and it's channels like this that keep my passion for space going and going!
The visual presentation of this channel is breathtakingly well done.
Dr. O'Dowd, Thank you for opening up the scientific research and related healthy debate to us.
Very impressed with this video. I have always been interested in astronomy and physics. It was things like this that drove me to enter those professions. Thank you for feeding my insatiable curiosity about the universe and the wonders that we discove
When I was really young and learned about the expasion of the universe I thought of it like a Balloon. That hasn't changed
I always thought of it as a ripple
When I heard it, it was told like it was an explosion of matter from a singular point of infinite mass and energy and I was instantly like oh that sounds like a black hole... wait we're inside a black hole.
So, hopefully none of us will be around when it bursts.
Yes a 4 d ballon
@@chanceassembly7444 it's more like being on the surface of a balloon that's expanding
"(Space/)Time is a flat circle."
- Rustin Cohle, True Detective
All circles are flat
@@MathaelTheDestroyer everything flat is a circle
Earth is flat
@enigma locally,Yes.Globally NO. are you a flat earther?
@enigma No.HELL NO
Thank you for making these videos for laypeople like me to (somewhat) understand, and marvel and ponder over.
When we look out into space we are looking back in time at a universe that was denser, hotter, and smaller. Of course it is going to appear as though the expansion is accelerating when we are in a broader space here and now, broader than the space we are looking at in the past, in any direction
so, will we have flatuniversers and globeuniversers now?
don't forget the saddleuniversers either
@@csehszlovakze they're just silly though
@@discomfort5760 how dare you! #teamsaddleuniverse
@@dewalderasmus8655 You know what they say about your worldview? It's all CROOKED
@@discomfort5760 all i'm saying is do some research and I think you will find the universe is a saddle. we have a meeting every Sunday in the saddle universe society club
hearing it from a science channel that finite might be a reality for our universe has somehow scared me much much more than infinity - what is this emotion.
claustrophobia?
Existential dread?
For me personally an infinite universe lends itself less to a creator (and/or being a simulation) while being finite doesn't prove there is one... It certainly makes it seem more of a possible option. That makes me more uncomfortable than i thought it would.
🤯 ikr
A realization ,that maybe your original thought could be ....or could not be. Epiphany , maybe ?
Like Singapore Breaking News, I also listen to spacetime while I play games. I tell -myself- I'm getting brainy though. It might be working too, I recognize more words/diagrams than I did at the start. (obligatory "you may think it's a long walk down the road to the chemist but that's peanuts to space! Listen-!" and so on...)
1:23-1:39 What if everything we know as our "universe" is just a bubble in a solid rock on a much larger scale?
And what if what we think is "freezing" is actually the wave's final impact residue?
Thank you for making this at least somewhat understandable by big dummies like me. I don't pretend to understand most of what is discussed, but feel a little proud of myself that I am at least follow along and not be totally lost....well most of the time. :p
The visuals on this video are outstanding!
From our frame of reference, light from the very edge the observable universe just reaching us was emitted right at the big bang, but the expansion of space has extended its journey. Does that mean we're looking at a magnified view of something tiny? And if so, as you go out and out (fixed in our frame of reference), the universe gets smaller, until it's a point.
That would seem like closed to some degree, I'm not sure about in the wider sense.
was on sabines channel watching "if the universe is expanding, what is it expanding into"... and now im here!
be careful with such strong statements... "now", "here", "im"
2:18 small typo, your maths symbols briefly switched back to LaTeX commands before going off screen.
Impossible. They are allergic to LaTeX.
@@bahumatneo Source? 😂
Oh thanks I wondered what happened there
Perhaps that was intentional, and a joke?
Ah, LaTex, memories
Great question. The fact that space (perhaps not the universe) is infinite *_blows my mind_*
"The universe is finite its resources finite if left uncheck life will cease to exist" *Purple Grape*
In order for something to grow it has to grow into something even the incredible universe there is something else there there has to be and it blows my mind thinking about it, I love space
Can you do a video on what it means to say the universe is ‘flat’? I find it confusing because if the universe is expanding in all directions, how can it be flat? Also, if you could explain what the gravity graphs mean in relation to to a flat but expanding universe that would be amazing!
The space in which galaxies and stars exist is not infinite, space itself is
Boy do I love knowledge and theories of infinite possibilities. The mind is filled with madness and is full of vanity.
2:19 When (La)TeX suddenly decided not to parse your symbols anymore
Me: Heyo, need a plusminus sign here
LaTeX: *groan, can't you just copy/paste a UTF-8 glyph? I feel lazy today...
@@ANDSENS or tell me to go into math mode.
I Really Like These Smart Guys Stuff .
No Seriously Best Video Yet .
Yohoo!! I pretty much understood this whole episode!
Half-way to the video, I was getting so excited, getting so far... and as the ending started to near, it became a nail-biter.
And finally a cliffhanger............
This changes everything. Literally.
This is literally performance art. I'm amazed he can keep from laughing for the entire video. What a pro.
With all the various cosmological options theoretically, it sounds like the elephant and the five blind men metaphor. Depending on exactly what we’re observing, that’s which aspect we see. What if we put them all together?
Loved the Douglas Adams reference at the very beginning :)
I caught that too!
That Adam Douglas opening (from H2G2) got me at "mind-bogglingly"
11:30 If, if and buts were candy and nuts, we'd all have a Merry Christmas!
The only channel i feel too dumb for, but yet find it incredibly interesting
This shows the importance of experimental thinking, where you create hypothetical scenarios in order to see how the physics works out.
@Prowler Cam Actually religion was invented primarily as a means to solidify social values and morals. Without religion humankind could never have progressed. Of course things are different today where we don't need religion to be moral.
Great video, Space Time team! ^_^
What about a closed but still flat geometry like a torus though (specifically a 3-torus embedded in 6D space so it stays flat)? Although, in the game Asteroids, the universe is a 2-torus (which would require 4D space to stay flat) but doesn't require an actual embedding space since it's a simulation.
P.S. - Pretty please could y'all make a video about Sir Roger Penrose's objective collapse interpretation of quantum mechanics? ^_^
I am glad someone had bring up this
+1 for wanting a video on objective collapse!
swear down, i'm not even a physicist and this is best show on YT
Luv this channel gets my brain going.
An episode on better explanation for positive curvature finite universe and expansion so no big crunch type scenario.
Is it like a sphere that keeps expanding in volume yet the surface will always loop?
Yep!
Imagine an inflating balloon
When ʻOumuamua comes back around with Voyager 1 orbiting it, then I'll believe you, Matt....
Oh geez. Hey Matt, which challenge would you find more probable. 'Omuamua + Voyager; or pig flies?
This is by itself an interesting series of problems:
Can even Voyager 1 HAVE an stable "orbit" around Oumuamua? (mass problem)
Would solar pressure destabilize it? (beyond the ice line, assuming not outgasing)
[Asuming no mass loses, like if laser beam powered] -> How much time it would take to change their trajectories of both so they can "meet" at relative speeds slow enough for an orbital capture? (asuming you are not heating them enough to melt/vaporize their surfaces).
Could both of them be redirected towards Earth at the same time? (the gravity tractor effect of Oumuamua over Voyager 1); Or should each of them had to be individually accelerated by different beams?
6:50 I remember the statement "Energy results in positive curvature, due to its positive gravitational fit" in the video "Secrets of the Cosmic Microwave". Can someone please explain me what "positive gravitational fit" mean without going into too much depth?
There is no possible way to know until we develop such advanced space travel that we can actually transcend the boundary or travel past the "edge" of the universe. OR die trying.
Love the occasional Hitchhikers Guide references. 👍
Yes the quote and the bunch of flowers in the graphic (can't spell petu.... oh you know what I mean)
2019 flat earthers, 2020 flat universers
Both wrong...funny
NOT a coincidence my friend. Soros up to no good again.
Please tell me how different our observations would be under the following set of assumptions,
1. The Universe has always been there
2. The Universe will continue forever
3. The Universe is infinite in size
4. There is no such thing as gravitational attraction. What we experience is the partial blocking of an all pervading force of repulsion
16:15 Your videos are great and great in the background of a gaming session. 5/5
In a recent episode, you responded to a viewer's invocation of the law of energy conservation in objection to something you discussed by stating that the conservation of energy applies on a local scale or to a closed system but not to the universe as a whole. So, here is my question: If some process at play in the broad universe creates or destroys energy, could you not draw an arbitrary boundary around the event and show that energy was created or destroyed locally or within a closed system?
I think the part you're missing is that drawing an arbitrary boundary is an illegal move. Any boundary you draw has to be "real" in the sense that you know for a fact that energy cannot cross it. "Closed system" is right, but "local scale" isn't because you can't arbitrarily ignore energy flows across the boundary and call it closed.
As for the universe, I guess the jury's still out on whether it conserves energy over its whole lifetime, so that's a separate discussion.
@@musicalfringe wrong! Start up the stars war music. As he tries to defend his personal interpretation.
@@thewizzard3150 I would dignify your pathetic attempt at sealioning with a response, but you couldn't even be bothered to finish your sentence 😂
@@musicalfringe see! I told you. I suppose the sealion reference means something in your own mind.
According to the anthropic principle, it’s infinitely more likely we’re living in an infinite universe, because theoretically, one infinite universe contains infinite number of intelligent life forms, whereas one finite universe contains finite numbers of intelligent life forms, infinitely less than one infinite universe.
Šimon Rataj universe isn’t infinite dumb dumb
If the universe were infinite then there wouldn't be stars that are older than the universe (as currently claimed that some are), because the age of the universe would have to be infinite.
The universe, by definition, includes "all existing matter and space". A universe of infinite size would have to be of infinite age. Because the universe is apparently expanding; that defies the idea of it being of infinite size, or being of infinite age. Because it is expanding it had to have started somewhere and at some time.
@@stevelux9854 How can a star possibly be older than the Universe/big bang?
I know, right? Until very recently there is a star that was being claimed to be older than the universe. This just exemplifies to me that there are a lot of things that scientists simply seem to be guessing about. Just one of the videos: ua-cam.com/video/jiSwvxA5v4Q/v-deo.html
You can believe me that the part of the universe we can’t see is much nicer than the part we can see.
Man.. you're a clever boy... nice work again...
MRW when he says "spacetime" at the end: "Hey, that's the name of the show!"
_Roll credits_
Love you Matt, you have plenty of subscribers from Greece
Ισχυει!
Σωστός
Swstos
Could the universe have had different geometries at different points in time as the universe evolved ?
The Universe is therfore slightly positive curved. Using Complex geometry we can define multi and paralell universes.
5:00 Hahahahaha, that jab at flat-earthers! 😂😂😂
definitely shots fired
That was BRILLIANT!!!!
I'm just waiting for for someone to claim that if the universe is flat then the Earth MUST be flat too!
@@kirkhamandy
Maybe we should take bets on who claims it first.
@@kirkhamandy Nathan Oakley or maybe Allegedly Dave...There is just so many to choose from!
Is there a way to determine how the geometry of the universe changes with time? For example, could we tell that it was more closed in the past or had a tighter curvature? And is it possible for it to become open in the future?
At the present (13,4.bl.) the Universe the proto mass ⊙ flouting around in a Browning spirals ☆
That makes up the fabric ☆☆☆
It is unlikely that something infinite can become finite or vice versa.
@@gravitonthongs1363 I agree with you about that, but we seem to be in the minority.
Sam Harper
It is also possible that there are fluctuations and the observable universe is mostly positively curved surrounded mostly by negative curvature or vice versa.
I think anything but infinite space creates force value fluctuations which we don’t observe.
You forget the cause of all spacial curvature.. Causes i should say, there's only two: mass, which causes inward curvature (damn Higgs field), and dark energy, which is/could be (?) just a small positive curvature. We don't know what causes it so we don't know if it can change. If you look at any of those block diagrams of spacetime it shows several changes in the value of dark energy---including the start and stop of the early 'initial' expansion, but also a slow increase in it's value (hyperbolic by the look of it) in later times. I would think that they have some motivation for these changes.
So, I'm relatively new to astrophysics and relativity, so go easy on me.
I just finished watching the Space-Time video asking whether or not our universe exists inside a black hole, followed by this one that discusses the size/shape of the universe. It got me thinking about the expansion of the universe. IF our universe does exist inside a black hole from a parent universe, can't the expansion of our universe be explained simply as the black hole in which we exist growing in size at it "ingests" more emery/space-time? Does that make sense? Is our universe expanding because the black hole in which it exists is growing?
Just a thought.
this is just something I've dreamed but: the universe is a manifold.
we are in the vicinity of all other galaxies to begin with, then we break apart into separate "tubes" and at the end we come back together.
i hate to bring deity into this equation but there is such a thing bringing us all back together in the end.
could it be possible that there is an unusual amount of mass in our local visible area that could cause a local curvature deviation while the rest of the universe maintains a different state?
Sure that's possible. That's the problem with ideas about what is outside of the observable universe... you can't observe it, so you can't rule out anything. Note that these researchers start out with a model of the whole universe (beyond what can be observed), which amounts to making a lot of assumptions.
goes without saying
or then it is bubbles in bubles
I’ve always found that a positively curved universe makes the most intuitive sense, and a negatively curved one the least, with flat stuck in between. I wonder how many others feel this way as well.
In any case, we should not be too quick to accept or reject any findings on the curvature of spacetime, as it is still early days and we should strive to avoid any potential confirmation bias.
the universe is under no obligation to make sense to you.
serges I agree
yup agreed
@@alien9279 Even in 4 dimensions, a HOMOGENEOUS negative curvature cannot be extended finitely, much less infinitely. The closest thing to a REGULAR negative curvature is the inside of a torus, which maintains uniform curvature on a "latitude line" around the greater radius of the torus, but varies in curvature as you move on longitude around the lesser curve on a "longitude" line, becoming positive curvature on the outside of the torus. That's why the lower dimensional representations of negative curvature shown are always finite and truncated.
It is true that the universe is under no obligation to first order to make sense to us. However, it is problematic to assert that what we say means anything when we try to assert something we don't understand. Science is the attempt to make sense of the universe. The universe may transcend us, but WE can't.
The bias is itself something worth understanding. I like the idea of a finite universe better because the alternative is somehow more daunting.
0:04 I'm surprised that nobody noticed that was is quote from the Hitchhikers Guide to the Galaxy.
this made me think of something strange ... it seems like it's possible for the values that determine the curvature of the universe to change over time (for example as dark energy increases and mass remains constant) and the universe is probably very close to flat either way, but there's a discontinuity between less than or equal to zero and greater than zero where the size suddenly becomes finite ... what happens if an infinite universe wants to become finite or vice versa??
Love the HHGTTG reference at the beginning
So the game Asteroid was even more physics-accurate than we thought -- keep going in one direction and you *will* eventually wind up back where you started!
Yes, but it's Astroids Deluxe. The rocks rotate. MUCH more realistic! 👍
No. The geometry of asteroid is a torus , that has 0 curvature but is compact; this is not the geometry of the sphere
You know it's hard out there when PBS needs a sponsor for their videos 🤣🤣
Why can’t I for once hear: “ we are 100% sure that the universe is …..”
we are 100% sure that the universe is pretty big, bigger than Earth at least.
"Of course science doesn't know everything! Otherwise it would just- stop."-Dara Ó Briain
Ummm...
We are very small and can't observe or imagine the leinght of our universe.
We aren't even close measuring our galaxy or nebulas.