How Much Of The Universe Can Humanity Ever See?
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- เผยแพร่เมื่อ 28 มี.ค. 2023
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There’s an absolute limit to our access to the universe beyond our own galaxy. There’s a limit to what we can ever hope to explore or send signals to, and a very different limit to what we can ever hope to witness. Today we’re going to explore the latter. We’re going to figure out the absolute limit of our future view of the universe, and of the universe’s ability to influence us. Next time we’ll turn it around and ask: how much of the external universe can WE potentially influence, and even explore?
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Props to the camera man for going that far just to get the footage.
Incredible, dedication..
Hope he got enough per diem.
Outdated joke
@@SamiSyed-br4uk Can a joke truly be outdated? 🤔
@@mrfake5251 its irritating after so much of use
Douglas Adams quotes will win my heart every time ❤️
This quote is subject to a copyright dispute filed from a time machine whose own existence is being debated in the next courtroom.
NORMAL SERVICE WILL BE RESUMED AS SOON AS POSSIBLE……
I had the 42nd like 😅
Take A Moment
Hi there Monkey Man.
42.
Get over it
Stay Safe and
Stay Free 😅🎉❤
How many of us continued the quote in our head?
"I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
Kudos for the team involved in doing this animations. They REALLY help understanding these advanced topics
Speak for yourself. I don't understand anything after "Space" and "Time"
Is it the and part
@@vkvk3525😂😅
This was the BEST explanation of the subject I've ever seen! I understand the principles but had difficulty conceptualizing the 'edges' of the universe. It will take a few rewatches and lots of pausing, but I'm certain I will finally wrap my head around this. Thank you!
Definitely gonna be watched a few more times by me.
Kurzgesagt did a video on the topic a year ago. Check it out: th-cam.com/video/uzkD5SeuwzM/w-d-xo.html
I agree.
@@paulhopkins8148 yeah I too had to re-watch the episode to properly conceptualize the space-time diagrams and to better understand how those later started to curve.
and then forgetting it 🙁
I love that you're wearing a shirt that says, "Heat Death is Coming" while talking about the expansion of the observable universe.
We appreciate the little things as well
Nice detail.
So cool...
Typo at 2:18 wrt plasma years.
What a magnificent episode. And that's saying a lot, all of your videos are incredibly good.
Up for this
no such thing as magnifix or lot or etc or not, bix s 1uferiox bloat, doesnt matter, cepuxuax, outx, can outx any nmw s perfx
I subscribe to this completely. I wanted to praise it in a comment too, but there is actually nothing to add.
@@zes7215 adverb verb noun adjective, noun verb noun adjective adverb noun adjective!
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space...”
Thanks so much for the *Hitchhikers' Guide to the Galaxy* reference -- there is a tiny corner of my heart that is forever Douglas Adams.
PBS Space Time is the best! I always struggled to grasp the idea behind diagrams for each of this horizons and hoped that someone will make a video explaining it and there is no surprise that Matt did it. I will still need to watch this episode again to be able to understand it fully but it is great to have this video.
I absolutely love these videos deep diving on conformal mappings! It's such a powerful tool in GR.
You ain't mapping
It ain't happening
GR seems to be one of the most reliable theories besides QM and it's CC, one of the few constants we can count on. I wonder if dark energy can be explained by expansion alone or if properties of empty space taken for granted might play a role, for example, space that has never seen certain waves in the layers of std model particles like neutrinos. Don't forget comoving space!
I normally keep up, but this one will require multiple re-watches. And for something I thought I already understood! Bravo for helping me see deeper into the subtleties of the idea.
Though... it's also an illustration of something I heard said, that a professor's job is to make complicated things simple... and simple things complicated. 😜
Always a great day when a new Space Time episode is released!
This is hands-down the best reference I’ve seen to study conformal diagrams in FRW spacetimes. I’ve struggled with them a lot in the past from books and papers; the effort put into this animations has made them my go-to reference right now. Keep up this amazing work!
Not only I am impressed by how much new information on a topic I thought I grasped I learned from this episode, the way it was presented was absolutely beautiful. I greatly appreciate the effort spent on making this episode. Give the person responsible for the graphs a raise!
How many time can we rediscover the spacetime diagram ? It'll always blow my mind !
Quick edit : this is how to science vulgarization works. I'm not a fan of math, never been easy. Yet, from particules interaction, to the physics of black holes, expansion, dark matter/energy, geodesics ... We've learned a lot of complicated ways to represent GR to quantum mechanics, it's awesome ! Thanks Matt and your team
The left path at 5:48 looks suspiciously fast though.
Spacetime is strangely arousing...
Too bad Hermann Minkowski was long dead before the rest of the world knew how to use it.
New tools always gives us a fresh look. Look at how neural networks sped up interpretation of the data we had for decades. That blackhole picture we took came from collaboration between labs around the planet allowing us to use the size of the Earth as an instrument. Quantum physics that led to really high definition T.V.s also lead to us understanding how to communicate better in space, calculate travelling salesman problem much faster, get to look for Higgs and find it and so on. As long as our understanding improves so will our interpretation of current data I suppose. But it is likely that we will find ourselves having to have to recreate rare events closer to home as we slow down in that progress.
Edited to add:
I say this because some basic things like the periodic table or the Standard Model really seems to be it for the foreseeable future. There are possible game changers out there but more on the disproving side. A weird one is the Kastler Brossel labs result vs. the Berkeley result for measuring the g-2 factor for ruling out non-observed phenomenon thus far. It's odd when only like 3 people can carry out an experiment and they disagree but certainly interesting to see. Afterall there are candidates for dark matter like the weakly interacting massive particles but none globally accepted.
It's definitely worth keeping an eye on, though I'm really expecting more from anti-matter experiments.
@@Mishanya442 -- Yes. They've made the same mistake in at least one previous video. I thought the visuals were great overall, though.
As you told me to imagine being a photon spat out by a star near the beginning of time, racing towards the Milky Way against expanding spacetime, I could feel myself red shifting across the decelerating horizon. Thank you for that superb imagery!
That was genius
So are you a particle or a wave.
i'll have what he's having
@@Duiker36 probably
@@Duiker36 😂
This is one of the best episodes, describing the basic concepts and definitions leading to a better understanding of time and expansion and the CMB that I've seen in a while. Good Job.
This has to be the best-animated video on TH-cam for an educational topic. Coupled with the writing and Matt's ability to present the material, and you've got some of the most beautiful work ever done on this platform, something I do not say lightly.
Mad props to you guys, and thank you for absolutely everything you do.
I'll be re-watching this one a few times to understand all of the nuances. Great episode!
Great episode! Very well explained, and a spacetime diagram that Georgia O'Keeffe would be proud of. Thank you, Matt.
Yes 🙌🏻 for the Hitchhikers Guide to the Galaxy reference!
Being early to a PBS Space Time TH-cam video is great, Quality content is always worth a watch.
I loved this episode!!! So beautiful and eloquently explained to someone familiar with some of the concepts here (space-time diagram for example) but then going further and expanding on those concepts to explore some of the largest meta-questions in cosmology; How much of the Universe will we ever see? When will the Universe past the Local Group start to recede away? and many other questions on the same topic. So excited to watch the next episode of Space Time!
The whole concept of dark energy "kicking in" always makes my nose twitch. Was it waiting for an invitation?
you do such a good job please never quit making these
At 2:20 there is a typo: I says the CMB was emitted after 380,00 years, instead of 380,000. 🙂
I came to the comments to see if the observant viewers saw the typo, too. I was not disappointed.
I still find it rad that we only need around 50 digits of pi to calculate the circumference of the currently observable universe to within the accuracy of a single proton.
Not true. There's a lot of uncertainty in the measurements of the age of the universe and its radius. The hubble constant if famously difficult to pin down.
EDIT: Misinterpreted the comment. Kumquat is right about his statement.
@@DKFX1 Requiring more certainty in measurements that aren't pi doesn't mean you need more than fifty digits of pi. Do youtube commenters have to hold their breath when they type because they can't do two things at once I wonder?
@@plat2716 Nice one.
I recognize the difference upon considering your classy comment, but digits of pi mean very little theoretically in terms of accuracy measurements if your constants are not equally precise or more so.
@@DKFX1 No problem. Maybe after one more classy comment you'll finally understand what people mean when they say you only need 50 digits of pi for this.
They're saying IF you had perfect measurements you would only need 50 digits of pi to get that level of accuracy. I shouldn't have to explain this to someone who can write complete sentences but hey I guess my expectations are too high for people who seem otherwise intelligent and articulate.
@@plat2716 The comment can easily be misinterpreted. A more correct way to phrase it according to your interpretation would be "you would need only 50 digits of pi" as opposed to "you only need 50 digits of pi". But one thing that cannot be misinterpreted is your terrible personality and attitude.
I loved that shell analogy and spacetime diagram; it was very intuitive. I am happy I got to live at a time where there are still stars and galaxies in the sky.
This video was made for me! I have been drawing these things I called light leaves with the same teardrop shape and then someone pointed me to the Davis and Lineweaver paper and it explained everything but I understand it a lot better after watching this video!
"You could imagine the night sky as a set of shells" So the geocentrics and their heavenly spheres weren't entirely wrong, funky! I love when coincidences/connections like this happen
I thought the same thing, with the pinprick stars thought to be windows into Eternity, which in a very loose sense some of them are. Great metaphorical echo!
Geocentrism and heliocentrism describe the relative movement of bodies in the solar system. That is not relevant to the ideation of the night sky as a set of shells, which is relative only to the observer’s position and does not imply any movement.
@@y11971alex He's very obviously talking about the imagery, not claiming that it's a literal return to the Ptolemaic system.
Any point in an infinite plane or sphere is legitimately "the middle" from its perspective. Hence, the Universe actually does revolve around us.
@@theprogram863 you can never quite tell though
4:15pm release for me! Do this more, please
Gmt - 8 ?
Same lmao
"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." Great video :)
I like the background sound/effect/music that comes in when Matt starts the epic explanations.
Really unique way of representation through layers. 👍
Idk if it’s my headache, but this is the first video in a while that I struggle to understand the material. That is GREAT NEWS, I love learning new stuff! Great video!!
I was literally the opposite, mostly dont get it, but these diagrams, makes it sense.
"Seeing is believing", knowing is power, and Virtual Work, being here-now-forever instantaneously.
Beautiful video Matt; in my opinion one of the best of your great channel. I had to watch it twice.
Loved the hitchhiker reference. Well explained as always.
What a fantastic mind bending episode! Thank you!
This is one of my favorite episodes.I have never fully understood how we can map the CMB but there are objects whose light has not yet had time to reach us. 🤩 This makes so much sense now. Thanks!
Simply the best cosmology source on you tube.
I've always been confused about how space time diagrams and light cones worked until now. Phenomenal animation and explanation. 🤓
Really hard for me to follow and grasp.. but I trust you know what you're talking about Matt! :D I'm glad it makes sense to you lol
"the sky will finally be dark."
chills imagining that. just chills.
Thank you for FINALLY providing an explanation of where the CMB comes from and how it relates to the size and geometry of the universe. I have seen the CMB invoked so many times without a real explanation other than "it comes from the big bang"
"Where we're going we won't need speed limits" ☺️
Before watching video: Well I know the observable universe is our hard limit.
There are exceptions. We've used gravitational lensing to see beyond the sphere that is the observable.
@@oracleofdelphi4533 I haven't watched the video yet, but I don't know how one could use gravitational lensing to see more distant objects. It should allow people to see distant objects more clearly, but not from farther away than the speed of light would allow. Am I missing something?
@@oracleofdelphi4533 That would actually reduce max range ( light covering a longer distance for not being in a straight line). It does let us see distance objects better in some cases. But C is a hard limit so max distance is limited by time.
@@oracleofdelphi4533 It makes objects appear distorted or at a different angle from where they actually are. But it can't make us see beyond the visible universe.
Y'all are getting into the weeds in terms of optics. Gravitational lensing collects light that would otherwise be too dispersed to see. This really has little to do with observable distance. Rather this is a helpful telescopic lense, thus the lensing part
This video was right on the edge of my event horizon of understanding, and expanded it, thank you.
While watching this video, I realized that space and time really are the same thing. When we look into the sky, we are looking into the past just as much, if not more than, we are looking at a far-off object.
It just never truly occured to me that at night we are looking into the distant past
I knew the light we were seeing was old but it still felt like I was looking at an object that was far away. But that's actually a weird way to think about light that is depicting phenomena that may not even exist anymore, especially as the space continuously changes.
I was just so used to "oh, the far off stars! Maybe someday we will explore them, like distant mountains!" But no, they are so unfathomably far away that we cannot experience them as we are now. And it seemed like the past was just a concept, an artifact of memory, and the only thing that really existed was the present.
But my whole life I could physically look into the past from the light of other stars as soon as my planet shielded the light of the star nearby. Every dozen hours we have the chance to look into far distant times.
Wild.
The visible universe is but one subatomic particle in a giant spacewhale.
Yeah it is very hard for our brain to process the size of the universe accurately but there's an easy trick you can try if you want.
Close your eyes and picture in your mind the entire size of your mom, and then double it...
That's pretty impressive isn't it?
@@Reth_Hard A spacewhale is bigger than any human can comprehend.
The animation makes it so much easier to grasp the concepts and ideas! Thank you!!!
What an amazing video, the visuals really clarified a lot of things that I was foggy on when it came to this topic, thanks a lot!
There is a typo 2:14 where a 0 is missing. It says "380,00 years after the big bang" - it should be "380,000 years".
They should re encode the whole video, delete this one and reupload it.
06:36 - I think you're right when saying DE "took over" at a certain point, billions of years ago. I think it likely started right at the beginning, but its effects only started to 'dominate' later on. If it didn't exist at the beginning, the Universe would've collapsed back in on itself and we wouldn't be here. You can see how the rate of change of the curve starts from right at the beginning - Dark Energy (expansion) must've therefore been having an effect, albeit a weaker effect earlier on.
My hypothesis is that spacetime (whatever it's made out of) is a substance, and that substance is entering our universe at all locations simultaneously. The more spacetime we have in our universe, the more "space" and "time" there is for new spacetime to enter from outside, so it gradually accelerates in expansion. Probably wrong, though! Just some thoughts about the multidimensional realm in which we exist. I'd love to see someone with expertise to try to figure out my hypothesis on a mathematical level, though. Perhaps someone already has. I mean, every other idea I've had, I've found out some great mind had the idea decades/centuries ago! Ideas are timeless.
The idea is called Emergent gravity. Spacetime is a condensed matter/many-body system. There are a lot of papers on the subject.
I could tell you more if you were interested.
This is an excellent video, absolutely love the topic and presentation! Thank you!
This stuff is great. Can't express how much I love this.
I've always struggled to visualize how the light from the CMB reaches us, this is an amazing video. Thank you for making these
My thoughts exactly. Tbh, they didn't explain very much how exactly we are able to see it. But the video gave enough visualization tools to work it out ourselves intuitively. Especially the non-conformal chart showing how in the early universe, the things beyond the hubble horizon, has space expanding much faster than the speed of light despite the small size of the universe, then slowing down, and speeding up. It really made it click why we can see the cmb 14 billion light years in every direction. And yet, at the time the cmb occupied a small space(relative to the current hubble horizon).
If light is quantized, why doesn't it begin to stutter as it reaches the edge of where we can see it?
Light is quantized at a given wavelength, so if you stretch out the waves the quanta becomes smaller
What edge? There is no edge from the light's perspective.
Redshifting is based on the wave-like tendencies of light, and so while the total energy of light will be the same, the energy will be spread across a larger time, appearing as a lower frequency/higher wavelength or redder.
Light took speech lessons as not to stutter
The interaction of light with fermions is quantized... photons are a useful mathematical abstraction for calculating the interaction, but photons are not actually a "thing" that exists. It's just a way to talk about a very small part of the continuous electromagnetic field.
I don't think I've ever actually heard a clear description of the particle horizon until now. Awesome!
Wow, those bloopers were so funny and personalizing. WE need to do that!! Great work. Keep it going!
You might think it's a long way down the road to the chemist, but that's just peanuts to space.
Did anyone catch a view of the planets last night?
It was too cloudy in my area😞
Thanks! Interesting as alway.
Looking forward the futures episodes.
Outstanding job, as usual. Many thanks
I'm kind of curious to know if it would be possible for the CMB to fit in with with one of the latest theories that our universe is in a black hole...
By definition, the universe is, as long as it meets or exceeds critical density. It'd be a time-like black hole.
10:50 An analogy I thought of is that of an ant standing on infinitely stretchy rubber band. The ant starts at one end which is racing away at 100 miles an hour. As the ant walks to other side, though, the ratio of rubber band in front compared to behind is always decreasing (even though the length of the rubber band keeps increasing, and increasing much faster than the ant can walk). But because this ratio will eventually go to zero, that means the ant must eventually reach the other side.
7:40 the spacetime diagram that accounts for the expansion of space is SO COOL
This is really well put together.
🎉 yay science
So jealous of the people who can comprehend all or most of the intricacies involved in this episode.
You can too, if you put in the work.
It is not necessary. The understanding of things will change again in future centuries. 😉
@@monoptique621 Sure, if you remain ignorant now, you won't have to update your knowledge in the future.
@@michaelsommers2356 Yes. The difficulty lies in the fact of not having a global view of the entire "sky of the galaxies". In my cosmological model, the "sky of the galaxies" would be in rotary motion within the thickness of a titanic hollow sphere. The apparent inflation would be a temporary dilation.
@@monoptique621 Hahahahahaha!
it’s tragic yet strangely beautiful at the same time, that we can never discover everything. There will always be places to see and new things to discover. We will never get to see them all, but we will also never run out of new discoveries. We will always be explorers to the very end.
Love it that you also use These cool tranforming graphics on this topic, not seen like this before 😎
Oh - its gonna be depressing one ;D
Hahah thought the same and the commercial isn't over
I love these videos and learning about the universe, but there are times that I'd rather add videos to the watch later list in order to prevent being sad for the rest of the day hahahaha. Sometimes my mind is not up to the task.
could single quarks exist in an undefined state?
How could anything exist in an undefined state? By definition, you’ve not defined if it exists.
AFAWK, quarks can't be separated to large distances from each other because the color force increases with distance, so at some distance the binding energy between two distant quarks exceeds the rest energy of two more quarks, so quarks will be created in the vacuum.
@zzasdfwas by undefined, I mean a sort of super position. How should we know there arent quarks like that?
@Aaron Perelmuter same answer to you 👆
@@ludermathwig7022 Well of course there are. Quarks are tiny particles, just like electrons and just like the neutrons and protons they are a part of. Therefore, as all quantum objects can exist in a superposition, the answer is of course. Moreover, a superposition is not an undefined state, it’s a combination of every state possible, we just have no idea which and in what proportions.
Great mind-expanding video, Matt!
Great episode as always and just mindboggling. But less mindboggling after I watched it. The spherical shells concept was great at explaining this.
2:10 Does CMB actually travel? Isn't it always... here, since Big Bang happened in all places at once?
It's always here since there are always more photons from the big bang that are just now reaching us. Those photons have been traveling.
Yes, kind of,however the cmb is what it looked like at the time.
From what I understand, it *was* everywhere at once, 13.7 billion years ago. The reason its not always here anymore is because the big bang is not happening anymore. So the CMB 'travels' forward in time. I hope that made any sense.
The CMB appeared much later than the universe
if we detect it, then it's here. But the light we detect now was emitted some time ago from somewhere else, and we can reconstruct and project that. Any light which was emitted "from here" "back then" is by now far gone.
Same as when you look at the moon. The light of the moon is in you eyes as you see it, but you can mentally reconstruct the moon as a far away object which emitted (/reflected) this light
General relativity and quantum mechanics will never be combined until we realize that they take place at different moments in time. Because causality has a speed limit (c) every point in space where you observe it from will be the closest to the present moment. When we look out into the universe, we see the past which is made of particles (GR). When we try to look at smaller and smaller sizes and distances, we are actually looking closer and closer to the present moment (QM). The wave property of particles appears when we start looking into the future of that particle. It is a probability wave because the future is probabilistic. Wave function collapse happens when we bring a particle into the present/past. GR is making measurements in the predictable past. QM is trying to make measurements of the probabilistic future.
Do you just cut and paste this same comment on every popular science TH-cam video?
@@juliavixen176 LOL. I knew someone would bust me eventually.
Matt always finds a creative & unique phrase to end each video with “Space Time” ☺️👍
I like to think I know something about the universe. I like it more when Space Time proves me wrong, and I have to watch again to try figure it all out. Definatly something new and mind bending.
Thanx to Dr. Dowd for these videos... I know they are difficult to put together but they are excellent!
magnificent explainer! eagerly awaiting the next episode
Topics like this are so interesting.
All i can say is 'ouch!" That hurt. Cudos that I understood about %70 of that. Well done.
Thanks, Ive been waiting for this. It made sense that the cmb was both super far away yet fairly close depending on how you look at it.
thank you so much, i've been thinking about exactly this for years and you answered all my questions :)
Thanks for making me relax and find ideas. You are rock stars 🤘
One of the most interesting video you did! Really loved it
Great video, thanks!
Finally, it's the best PBS Spacetime episode of all time. You've really outdone yourself this time!
I’m reminded of a well written video about the simultaneous agoraphobia of just how kind bogglingly big the universe is and the claustrophobia of not being able to explore all of it and being trapped by the speed of light.
It also talked about the paper clip maximizer game.
link?
but if you find _that_ claustrophobic, the fact that you will be dead in what cosmologically amounts to no time at all, must be paralysing!
A very good reference right at the start.
So long, and thanks for all the vids. This is only a reference in return.
Matt, your episodes are always… brilliant! And I always come away from them, or out of them, feeling smarter, a good-feeling illusion! But this time, this once, I must say I lost my footing! My head went spinning and I went reeling. Boy, I’ll need to read up on the (new to me) concepts you introduce here, and then re-watch and re-re-watch this video until the moving coordinates and shifting and stretching spacetime eventually sink into my kilogram and a half of wet slushy mush that neuroscientists call the brain. You’re right: I had never seen those diagrams before. They’re fascinating. Thanks again for all the effort you put in making these videos a piece of art. Have you thought of getting GPT4 etc. to help you with them? 😉
Loved This Video! Can’t wait for the next one on this topic
My favourite yet!
Can’t wait for the next!!!
incredible work, truly.
I'm sorry I didn't mean to interrupt your super physicist video. It hurt my brain. I was just looking for a clowder video. 😂
Btw, Awesome video. I'm sure I will understand the universe before all the galaxies go cold.
This seems to be the clearest explanation I've ever seen. Would have liked a summary at the end of the sizes of all horizons defined, though.
Amazing episode, it is as much beautiful as it is soul-crushing x-x
Thanks for this. I had been thinking about it. The transforming diagrams were incredible.
Great episode, thank you!!
This is in the top 3 of the best PBS Space Time Episodes!