čas přidán 28. 03. 2023
Thank you to Brilliant for Supporting PBS. To learn more go to brilliant.org/SpaceTime/
PBS Member Stations rely on viewers like you. To support your local station, go to:to.pbs.org/DonateSPACE
Sign Up on Patreon to get access to the Space Time Discord!
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?
Check out the Space Time Merch Store
Sign up for the mailing list to get episode notifications and hear special announcements!
Search the Entire Space Time Library Here: search.pbsspacetime.com/
Hosted by Matt O'Dowd
Written by Matt O'Dowd & Euan McLean
Post Production by Leonardo Scholzer, Yago Ballarini, & Stephanie Faria
Directed by Andrew Kornhaber
Associate Producer: Bahar Gholipour
Executive Producers: Eric Brown & Andrew Kornhaber
Executive in Charge for PBS: Maribel Lopez
Director of Programming for PBS: Gabrielle Ewing
Assistant Director of Programming for PBS: John Campbell
Spacetime is produced by Kornhaber Brown for PBS Digital Studios.
This program is produced by Kornhaber Brown, which is solely responsible for its content.
© 2023 PBS. All rights reserved.
End Credits Music by J.R.S. Schattenberg: / multidroideka
Space Time Was Made Possible In Part By:
Big Bang Sponsors
John R. Slavik
Gamma Ray Burst Supporters
John H. Austin, Jr.
Diana S Polijar
Mark Daniel Cohen
Nickolas Andrew Freeman
Komentáře: 1 518
Props to the camera man for going that far just to get the footage.
Hope he got enough per diem.
@Sami Syed Can a joke truly be outdated? 🤔
@Mr Fake its irritating after so much of use
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
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.
@Paul Hopkins 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 🙁
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.
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.
Great episode! Very well explained, and a spacetime diagram that Georgia O'Keeffe would be proud of. Thank you, Matt.
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.
@Zes adverb verb noun adjective, noun verb noun adjective adverb noun adjective!
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!
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!
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!
This one wound up being a lot more complicated than I was expecting 😅. I'm very much looking forward to the next episode! Thank you for another informative episode and the super helpful charts! God be with you out there everybody. ✝️ :)
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
Typo at 2:18 wrt plasma years.
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. 😜
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.
Completely awesome episode. I was actually waiting for something like that for quite some time, even commented a couple of times here or at Sabine Hossenfelder's channel. Physics Girl also has a nice episode on it where she explains it with stones on a beach^^ Anyway, the animations were really well done and helpful and the video contains everything I ever hoped for.. And the best thing is: There is a second part!
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
@Michael Chui probably
@Michael Chui 😂
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).
I've always been confused about how space time diagrams and light cones worked until now. Phenomenal animation and explanation. 🤓
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 😅
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."
I'll be re-watching this one a few times to understand all of the nuances. Great episode!
I don't think I've ever actually heard a clear description of the particle horizon until now. Awesome!
Amazing episode. It's insane to think about far far future milky way life having no way to know the things we know now, such as proving thr big bang via the CMB. I wonder how a last billion year observation of light outside our local bubble would look like. Probably safe to imagine a starry sky with all stars slowly dissapearing?
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!
Fantastic episode, the animation and graphics helped me understand the material. Thanks PBS Space Time!
Always a great day when a new Space Time episode is released!
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!
This is an excellent video, absolutely love the topic and presentation! Thank you!
This really helped explain the comoving diagram, thanks! One flaw in the photon traveling video; I couldn’t figure out what I was confused by until I held a pencil in front of my screen and moved my phone so the photon stayed in place while the rest of the diagram moved. The Milky Way moves away from the photon at first, but starts moving back towards the photon after the pause at the 2X sphere. I know you care about accurate representation! For next week’s video, I would like to see this video redone without the pause and nail the expansion accurately. Also please be consistent with the photon being represented at the center of the wave packet. Then show a split screen, top, middle and bottom, where in each, the Milky Way is held in place, the photon is held in place, and the original galaxy is held in place, respectively. 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.
you do such a good job please never quit making these
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...
@Михаил Мищенко -- Yes. They've made the same mistake in at least one previous video. I thought the visuals were great overall, though.
Fantastic episode, your diagrams and instruction really helped we non Astro PhD types. Thank You !
Always enlightening and elucidating, and fortunately with such light whose photons are reassuringly within the Hubble Horizon. Thanks for a great presentation of the cosmos!
Great mind-expanding video, Matt!
I always feel like there's some fundamental flaw in the way space/time expands. It would seem we would be limited to what we can see of the observable universe, with every second being a more narrow cone of vision. Further, so much should have already passed us, leaving a big blank abyss.
Loved the animation as well. As for your question about our limits…how much does it matter? Old light from a young universe? Well put.
Really unique way of representation through layers. 👍
I actually thoroughly enjoyed the explanation of it all and I understood nearly all of it and it amazes me how us Bipedal apes that somehow are aware of our own existence is able to witness and understand things like this in some form. No matter if it's how things work or don't. It's still amazing that life exists as it does. ❤️🐦🥚🐣🐥🐤🐦❤️
Matt always finds a creative & unique phrase to end each video with “Space Time” ☺️👍
This stuff is great. Can't express how much I love this.
What a fantastic mind bending episode! Thank you!
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?
@Plat 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.
@Plat 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.
Thanks for this. I had been thinking about it. The transforming diagrams were incredible.
The animation makes it so much easier to grasp the concepts and ideas! Thank you!!!
Beautiful video Matt; in my opinion one of the best of your great channel. I had to watch it twice.
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"
Loved the hitchhiker reference. Well explained as always.
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.
Thanx to Dr. Dowd for these videos... I know they are difficult to put together but they are excellent!
I can't say I understood everything said in this video but it was fascinating all the same!! I hope that one day,when my mind has expanded along with my consciousness, I'll be able to intuitively comprehend every aspect of the world around me.
THIS clearly reflects that the mind does not produce consciousness on its own. It is an evolution with the environment.
Outstanding job, as usual. Many thanks
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.
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.
Question! Do to the red shift/blue shift of light in the universe(or some other method), can we tell where the center of the universe is roughly? And if so, where are we in relation to it?
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.
I like the background sound/effect/music that comes in when Matt starts the epic explanations.
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.
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.
A nature article titled "Double-slit time diffraction at optical frequencies" was published on 3/4... I am very curious on your opinion on this! :)
Very interesting! Thank you for the lesson! :)
Great episode as always and just mindboggling. But less mindboggling after I watched it. The spherical shells concept was great at explaining this.
Can you please do a video on if there is any relationship between the Bekenstein Bound and Shannon Entropy? Like if I throw a 1kg book into a black hole, does the bound grow more than if I threw a 1kg chunk of iron?
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.
I'm curious if AI will ever extrapolate new insights about our universe. Cosmology seems like one area where the I in AI, required would be too demanding for it but I'd like to know your thoughts and the collective reasoning out there on it.
thank you so much, i've been thinking about exactly this for years and you answered all my questions :)
I’d like to think we will be able to one day see all of the universe just based off of the statistical algorithms that we are able to figure out in the future that we can use to simulate universes :)
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? 😉
Could we in principle create a pair of probes that use direct counterfactual quantum Zeno effect principles and maintain the entanglement such that we put one probe outside the black hole horizon or event horizon and put the other one in and measure what's inside of it?
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.
Love it that you also use These cool tranforming graphics on this topic, not seen like this before 😎
I always wondered if we were to discover a stable wormhole even a smallish one in the future and it was connected to an area of spacetime much closer to where the observable universe lies, If we were to look through with a radio telescope what would we see?
Question: if a particle is TRULY a point… wouldn’t it be the same at all scales no matter what? Could the same photon be affecting hidden small scales?
As always I struggle to understand these topics but they are fascinating! If FTL travel is ever a real technology and assuming it can achieve distances faster than the current rate of expansion, then I'm thinking we'd be able to see more and bring that information back to Earth, right? (or wherever humans are living at the time). The idea of recording points in space with a FTL ship, putting that data in a storage medium on the ship, and then returning it to Earth is a really cool concept in itself.
Is it possible that we will one day discover some kind of quantum entanglement between the particles in the milky way and those of galaxies on other side of the universe? Could that not be used to then gather information of those regions outside our event horizon?
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
If theoretically given enough time (assuming a that a person lives forever) will our body expand so much with the space that signals from our brain won’t be able to reach our feet? Will we perceive things differently at that time or everything will seem normal as relatively everything is expanded exactly same?
Technically, you could see longer if you had strategically placed gravitational lenses station around the outermost parts. Some light that would not be possible might still go in a parabolic orbit around a black hole near the edge and then reflect to earth though it might not be possible to tell where it came from it.
Matt, what can you tell us about the war between time and space/time, as described in that other science documentary, Doctor Who?
I could feel my mind expand and contract with the shape of that space-time diagram 😶🌫️🤯 Seriously, thank you for providing some amazing visual representation and narration.
One of the most interesting video you did! Really loved it
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.
Finally, it's the best PBS Spacetime episode of all time. You've really outdone yourself this time!
Is the series on the brain's creation of time over? I was hoping for a few more episodes on that one :)
Dear PBS, this video is one I've been waiting for for 5-6 years. The question that I've been pondering all this time is this: How do you differentiate between the photons from the CMB and photons from distant galaxies that have undergone an enormous redshift? After seeing this video I think of 2 options; whether it is a different type of wavelength than light from another galaxy; or you get a different prism spectrum if you compare the light from cmb with light from a distant galaxy. Maybe a good subject for a new video??
it is the spectroscopic equivalent of "these sheep are really tiny, and those sheep are far away"
I love the universe spheres. What are the little artifacts at the bottom of them?
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. 😉
@MonOptique Sure, if you remain ignorant now, you won't have to update your knowledge in the future.
@Michael Sommers 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.
Is there a way to calculate/estimate how much of the universe we won't ever be able to see?
Could someone explain to me why the top part of the graph is limited by an infinite? I've never seen this type of asymptote before.
The first time I heard of space being able to expand faster than light was from the children’s book series “Do you want to be a Wizard” by Diane Duane.
Thanks, this episode answers a question I have had for a long time. How long before we start loosing the ability to see things.
This video was right on the edge of my event horizon of understanding, and expanded it, thank you.
"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.
@The Program you can never quite tell though
Amazing episode, it is as much beautiful as it is soul-crushing x-x
What about setting up "relays" where one group after another only shifts "half out" of our contracting horizon, so that messages can be passed from one horizon to the next? I imagine we could do that until all these horizons fully contract.... right?
Omg this is exactly the kind of question I have for physics! What if anything can humanity do to 'escape' the heat death and sustain ourselves through the multiverse. #BigDreams
What can we do? Nothing.
"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 :)
What do you think about toroidal universe with the huge black/white hole in its centre?
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 👆
@Lüder Mathwig 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.
Loved This Video! Can’t wait for the next one on this topic
Thanks! Interesting as alway. Looking forward the futures episodes.