Tap to unmute

How Much Of The Universe Can Humanity Ever See?

  • Published on Mar 28, 2023 veröffentlicht
  • 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
    Ian Jones
    Bryce Fort
    Peter Barrett
    David Neumann
    Sean Maddox
    Alexander Tamas
    Morgan Hough
    Juan Benet
    Vinnie Falco
    Fabrice Eap
    Mark Rosenthal
    Quasar Sponsors
    Glenn Sugden
    Alex Kern
    Ethan Cohen
    Stephen Wilcox
    Christina Oegren
    Mark Heising
    Hypernova Sponsors
    Ivari Tölp
    Vyce Ailour
    Zachary Wilson
    Kenneth See
    Gregory Forfa
    Kirk Honour
    Joe Moreira
    Bradley Voorhees
    Marc Armstrong
    Scott Gorlick
    Paul Stehr-Green
    Ben Delo
    Scott Gray
    John R. Slavik
    Donal Botkin
    John Pollock
    Edmund Fokschaner
    chuck zegar
    Jordan Young
    Daniel Muzquiz
    Gamma Ray Burst Supporters
    Lucas Kazakevicius
    Massimiliano Pala
    Aaron Molina
    Thomas Nielson
    Joe Pavlovic
    Ryan McGaughy
    Mark West
    Chuck Lukaszewski
    Edward Hodapp
    Cole Combs
    Andrea Galvagni
    Jerry Thomas
    Nikhil Sharma
    Ryan Moser
    Jonathan Cordovano
    John Anderson
    David Giltinan
    Scott Hannum
    Paul Widden
    Bradley Ulis
    Craig Falls
    Kane Holbrook
    John Yaraee
    Ross Story
    teng guo
    Mason Dillon
    Matt Langford
    Harsh Khandhadia
    Thomas Tarler
    Susan Albee
    Frank Walker
    Michael Lev
    Terje Vold
    James Trimmier
    Andre Stechert
    Paul Wood
    Kent Durham
    jim bartosh
    Ramon Nogueira
    Paul Suchy
    Ellis Hall
    John H. Austin, Jr.
    Diana S Polijar
    Faraz Khan
    Almog Cohen
    Alex Edwards
    Endre Pech
    Daniel Jennings
    Cameron Sampson
    Russ Creech
    Jeremy Reed
    David Johnston
    Michael Barton
    Andrew Mann
    Isaac Suttell
    Bleys Goodson
    Robert Walter
    Yury Kitaev
    Mirik Gogri
    Mark Delagasse
    Mark Daniel Cohen
    Nickolas Andrew Freeman
    Shane Calimlim
    Tybie Fitzhugh
    Robert Ilardi
    Eric Kiebler
    Craig Stonaha
    Graydon Goss
    Frederic Simon
    John Robinson
    Jim Hudson
    Alex Gan
    David Barnholdt
    David Neal
    John Funai
    Bradley Jenkins
    Cody Brumfield
    Thomas Dougherty
    Dan Warren
    Patrick Sutton
    John Griffith
    Dean Faulk

Comments • 1 518

  • Mr Fake
    Mr Fake 2 months ago +59

    Props to the camera man for going that far just to get the footage.

    • Louly
      Louly Month ago +2

      Incredible, dedication..

    • Fredrick Talbot
      Fredrick Talbot 22 days ago +1

      Hope he got enough per diem.

    • Sami Syed
      Sami Syed 20 days ago +1

      Outdated joke

    • Mr Fake
      Mr Fake 20 days ago +2

      @Sami Syed Can a joke truly be outdated? 🤔

    • Sami Syed
      Sami Syed 20 days ago +1

      @Mr Fake its irritating after so much of use

  • Koss
    Koss 2 months ago +102

    Kudos for the team involved in doing this animations. They REALLY help understanding these advanced topics

    • vk vk
      vk vk 2 months ago +4

      Speak for yourself. I don't understand anything after "Space" and "Time"

    • norton man
      norton man 11 days ago

      Is it the and part

  • Pete M
    Pete M 2 months ago +177

    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!

    • Paul Hopkins
      Paul Hopkins 2 months ago +7

      Definitely gonna be watched a few more times by me.

    • Pearly Dhingra
      Pearly Dhingra 2 months ago +1

      I agree.

    • FUG Slayer Nominee
      FUG Slayer Nominee 2 months ago +5

      @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.

    • alf beem
      alf beem 2 months ago +3

      and then forgetting it 🙁

  • Oskar Skalski
    Oskar Skalski 2 months ago +47

    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.

  • William Mogey
    William Mogey 2 months ago +20

    Great episode! Very well explained, and a spacetime diagram that Georgia O'Keeffe would be proud of. Thank you, Matt.

  • Samael 11
    Samael 11 2 months ago +17

    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.

  • deathzito
    deathzito 2 months ago +341

    What a magnificent episode. And that's saying a lot, all of your videos are incredibly good.

    • m4s0ok4
      m4s0ok4 2 months ago

      Up for this

    • Zes
      Zes Month ago

      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

    • Jos van der Spek
      Jos van der Spek Month ago

      I subscribe to this completely. I wanted to praise it in a comment too, but there is actually nothing to add.

    • bob Zombie
      bob Zombie Month ago

      @Zes adverb verb noun adjective, noun verb noun adjective adverb noun adjective!

  • CapoJachu
    CapoJachu 2 months ago +5

    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!

  • Shane Zanath
    Shane Zanath 2 months ago +2

    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 would like to remain anonymous

    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!

  • Nathan Wilson
    Nathan Wilson 2 months ago +1

    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. ✝️ :)

  • SauceGPT
    SauceGPT 2 months ago +228

    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

  • JS 2K
    JS 2K 2 months ago +102

    I absolutely love these videos deep diving on conformal mappings! It's such a powerful tool in GR.

    • James Driscoll_tmp
      James Driscoll_tmp 2 months ago +1

      You ain't mapping
      It ain't happening

    • John Gagon
      John Gagon 2 months ago

      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!

    • The Program
      The Program 2 months ago

      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. 😜

  • Sebastian Dierks
    Sebastian Dierks 2 months ago

    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!

  • Jason Fraga
    Jason Fraga 2 months ago +4

    I've always been confused about how space time diagrams and light cones worked until now. Phenomenal animation and explanation. 🤓

  • EJ Bert
    EJ Bert 2 months ago +9

    I'll be re-watching this one a few times to understand all of the nuances. Great episode!

  • Jake Allen
    Jake Allen 2 months ago +3

    I've always struggled to visualize how the light from the CMB reaches us, this is an amazing video. Thank you for making these

    • panner11
      panner11 Month ago

      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).

  •  Nightscape
    Nightscape 2 months ago +4

    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.

  • DroneBot Workshop
    DroneBot Workshop 2 months ago +47

    Always a great day when a new Space Time episode is released!

  • Roli Rivelino
    Roli Rivelino 2 months ago +24

    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!

  • Daniel M
    Daniel M 2 months ago +3

    What a fantastic mind bending episode! Thank you!

  • Zoltan Vaci
    Zoltan Vaci 2 months ago +2

    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"

  • lypse14
    lypse14 2 months ago

    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!

  • mossyfriends
    mossyfriends 2 months ago +2

    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.

  • Galadonin
    Galadonin 2 months ago +126

    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

    • Михаил Мищенко
      Михаил Мищенко 2 months ago +6

      The left path at 5:48 looks suspiciously fast though.

    • D
      D 2 months ago +2

      Spacetime is strangely arousing...

    • mvmlego1212
      mvmlego1212 2 months ago +1

      @Михаил Мищенко -- Yes. They've made the same mistake in at least one previous video. I thought the visuals were great overall, though.

  • Brian & Sylvia
    Brian & Sylvia 2 months ago

    I don't think I've ever actually heard a clear description of the particle horizon until now. Awesome!

  • ajdeem90
    ajdeem90 2 months ago

    Fantastic episode, the animation and graphics helped me understand the material. Thanks PBS Space Time!

  • Chuck Talbott
    Chuck Talbott 2 months ago +2

    This stuff is great. Can't express how much I love this.

  • CashFlowTV
    CashFlowTV 2 months ago +2

    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?

  • Allan Burns
    Allan Burns 2 months ago +6

    you do such a good job please never quit making these

  • fiskfisk33
    fiskfisk33 2 months ago +250

    Douglas Adams quotes will win my heart every time ❤️

    • Ms Zee Zed
      Ms Zee Zed 2 months ago +37

      This quote is subject to a copyright dispute filed from a time machine whose own existence is being debated in the next courtroom.

    • Pope Vimto Ripkeef Happysack XVIII
      Pope Vimto Ripkeef Happysack XVIII 2 months ago +12


    • Kommer Jan Allart
      Kommer Jan Allart 2 months ago +18

      I had the 42nd like 😅

    • Patrick
      Patrick 2 months ago +19

      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."

  • Ary Wahyudi
    Ary Wahyudi 2 months ago

    Matt always finds a creative & unique phrase to end each video with “Space Time” ☺️👍

  • Paul Deck
    Paul Deck 2 months ago

    This is an excellent video, absolutely love the topic and presentation! Thank you!

  • Bryan Hyde
    Bryan Hyde 2 months ago +1

    Fantastic episode, your diagrams and instruction really helped we non Astro PhD types. Thank You !

  • Lana Marie ASMR
    Lana Marie ASMR 2 months ago +1

    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.

  • Cole Coughlin
    Cole Coughlin 2 months ago +6

    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!

  • Keith Cooper
    Keith Cooper 2 months ago

    Great mind-expanding video, Matt!

  • Dr. Ricco Lindner
    Dr. Ricco Lindner 2 months ago +2

    Love it that you also use These cool tranforming graphics on this topic, not seen like this before 😎

  • Bert Pasquale
    Bert Pasquale 2 months ago

    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!

  • Anthony Narozniak
    Anthony Narozniak 2 months ago +5

    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...

    • Brian & Sylvia
      Brian & Sylvia 2 months ago +3

      By definition, the universe is, as long as it meets or exceeds critical density. It'd be a time-like black hole.

  • Joel Pinball
    Joel Pinball 2 months ago +2

    I like the background sound/effect/music that comes in when Matt starts the epic explanations.

  • amir tambe
    amir tambe 2 months ago +9

    Really unique way of representation through layers. 👍

  • Jed Gould
    Jed Gould 2 months ago

    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.

  • Neal Daniel
    Neal Daniel 2 months ago +1

    Thanks for this. I had been thinking about it. The transforming diagrams were incredible.

  • George Burdell
    George Burdell 2 months ago

    Thanx to Dr. Dowd for these videos... I know they are difficult to put together but they are excellent!

  • John Gagon
    John Gagon 2 months ago

    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!

  • Ugo Nunes
    Ugo Nunes 2 months ago +3

    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!!

    • Mark Freeman
      Mark Freeman 2 months ago

      I was literally the opposite, mostly dont get it, but these diagrams, makes it sense.

  • Werner Hoffmans
    Werner Hoffmans 2 months ago

    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.

  • arbinoypogi
    arbinoypogi 2 months ago

    The animation makes it so much easier to grasp the concepts and ideas! Thank you!!!

  • David Kenny
    David Kenny 2 months ago +1

    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.

  • Gem Indigo
    Gem Indigo 2 months ago

    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.

    • C2H5OH
      C2H5OH 2 months ago

      THIS clearly reflects that the mind does not produce consciousness on its own. It is an evolution with the environment.

  • Gonzalo Luis Borderolle

    Beautiful video Matt; in my opinion one of the best of your great channel. I had to watch it twice.

  • success meditations
    success meditations 2 months ago +3

    Loved the hitchhiker reference. Well explained as always.

  • Scott Hammond
    Scott Hammond 2 months ago

    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.

  • superhawk20002
    superhawk20002 2 months ago +1

    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.

  • Matthew Watson
    Matthew Watson 2 months ago +3

    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.

  • Pablo González
    Pablo González 2 months ago

    Outstanding job, as usual. Many thanks

  • Agent 8449
    Agent 8449 2 months ago +17

    "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

    • The Program
      The Program 2 months ago +1

      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!

    • y11971alex
      y11971alex 2 months ago +6

      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.

    • The Program
      The Program 2 months ago +4

      @y11971alex He's very obviously talking about the imagery, not claiming that it's a literal return to the Ptolemaic system.

    • David
      David 2 months ago +1

      Any point in an infinite plane or sphere is legitimately "the middle" from its perspective. Hence, the Universe actually does revolve around us.

    • Deipatrous
      Deipatrous 2 months ago

      @The Program you can never quite tell though

  • dmk
    dmk 2 months ago

    thank you so much, i've been thinking about exactly this for years and you answered all my questions :)

  • SunRey E
    SunRey E Month ago

    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.

  • Help Me Change The World
    Help Me Change The World 2 months ago +1

    Very interesting! Thank you for the lesson! :)

  • Ketracel White
    Ketracel White 2 months ago +5

    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

  • E
    E 2 months ago +1

    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?

  • Kumquat Lord
    Kumquat Lord 2 months ago +63

    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.

    • DKFX1
      DKFX1 2 months ago +8

      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.

    • Plat
      Plat 2 months ago +8

      @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?

    • DKFX1
      DKFX1 2 months ago +4

      ​@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.

    • Plat
      Plat 2 months ago +6

      @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.

    • Batman
      Batman 2 months ago +10

      @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.

  • Avaron Verdejo
    Avaron Verdejo 2 months ago

    Amazing episode, it is as much beautiful as it is soul-crushing x-x

  • m4s0ok4
    m4s0ok4 2 months ago

    One of the most interesting video you did! Really loved it

  • Josh Vader
    Josh Vader 2 months ago

    This is in the top 3 of the best PBS Space Time Episodes!

  • Bill Vinson
    Bill Vinson 2 months ago

    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.

  • Jim Griffiths
    Jim Griffiths 2 months ago +6

    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.

  • Steven Schilizzi
    Steven Schilizzi 2 months ago

    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? 😉

  • Censored Censored
    Censored Censored 2 months ago +1

    Matt, what can you tell us about the war between time and space/time, as described in that other science documentary, Doctor Who?

  • Joshua
    Joshua 2 months ago

    Great episode as always and just mindboggling. But less mindboggling after I watched it. The spherical shells concept was great at explaining this.

  • Hossak 2014
    Hossak 2014 2 months ago +2

    "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 :)

  • Matthias "Koschi" Koschnitzke

    At 2:20 there is a typo: I says the CMB was emitted after 380,00 years, instead of 380,000. 🙂

    • Sherlock Holmes
      Sherlock Holmes 2 months ago +1

      I came to the comments to see if the observant viewers saw the typo, too. I was not disappointed.

  • robopsychology
    robopsychology 2 months ago

    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! :)

  • Aric Blunk
    Aric Blunk 2 months ago

    This video was right on the edge of my event horizon of understanding, and expanded it, thank you.

  • Tim Hansen
    Tim Hansen 2 months ago

    Loved This Video! Can’t wait for the next one on this topic

  • John Dill
    John Dill Month ago

    Can you cover how Starship could be used to save the earth from a asteroid and/or comet?

  • Chris Brown
    Chris Brown 2 months ago

    Thanks, this episode answers a question I have had for a long time. How long before we start loosing the ability to see things.

  • Vineet Kansotia
    Vineet Kansotia 2 months ago +3

    So jealous of the people who can comprehend all or most of the intricacies involved in this episode.

    • Michael Sommers
      Michael Sommers 2 months ago +1

      You can too, if you put in the work.

    • MonOptique
      MonOptique 2 months ago

      It is not necessary. The understanding of things will change again in future centuries. 😉

    • Michael Sommers
      Michael Sommers 2 months ago +2

      @MonOptique Sure, if you remain ignorant now, you won't have to update your knowledge in the future.

    • MonOptique
      MonOptique 2 months ago

      @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.

    • Michael Sommers
      Michael Sommers 2 months ago +2

      @MonOptique Hahahahahaha!

  • beatsntoons
    beatsntoons 2 months ago

    Is the series on the brain's creation of time over? I was hoping for a few more episodes on that one :)

  • Ducu Soare
    Ducu Soare 2 months ago +1

    I have been trying to visualize what this video did for months now. Even thought about going into coding for this purpose. GJ, PBS.

  • richteffekt
    richteffekt 2 months ago

    "I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." Thank you for the opening ❤

  • Peter Petite
    Peter Petite 2 months ago

    There is something strangely beautiful about this, something poetic.

  • Regdu Geht
    Regdu Geht 2 months ago

    everything I ever hoped for.. And the best thing is: There is a second part!

  • radkerson
    radkerson 2 months ago +23

    If light is quantized, why doesn't it begin to stutter as it reaches the edge of where we can see it?

    • somanayr
      somanayr 2 months ago +1

      Light is quantized at a given wavelength, so if you stretch out the waves the quanta becomes smaller

    • XtreeM FaiL
      XtreeM FaiL 2 months ago +3

      What edge? There is no edge from the light's perspective.

    • Chris Paris
      Chris Paris 2 months ago +7

      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.

    • Mike Reherman
      Mike Reherman 2 months ago +3

      Light took speech lessons as not to stutter

    • Julia Vixen
      Julia Vixen 2 months ago +2

      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.

  • zombiemoses
    zombiemoses 2 months ago

    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?

  • CO
    CO 2 months ago

    I made it almost 3 minutes before my brain turned to mush. That's a new record!

  • Daniel Liberman
    Daniel Liberman 2 months ago

    I definitely need to watch this video a few more times before I finally convince myself I cannot understand it.

  • Liam Rappaport
    Liam Rappaport 2 months ago

    That graph at 8:18 is trippy. As I oscillate my eyes through a range of different focuses, the vertical lines change from greenish to blueish to reddish when viewed on my TV.

  • Dan E
    Dan E 2 months ago

    more of a bachelor of arts type myself but space Karl Urban really makes this stuff easy to understand

  • Liberty Jones
    Liberty Jones 2 months ago +4

    "Where we're going we won't need speed limits" ☺️

  • 058
    058 2 months ago

    7:40 the spacetime diagram that accounts for the expansion of space is SO COOL

  • John Gagon
    John Gagon 2 months ago +2

    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.

  • Test Rabbit
    Test Rabbit Month ago

    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?

  • Cameron Hunt
    Cameron Hunt 2 months ago +2

    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.

  • za chrome
    za chrome 2 months ago

    What do you think about toroidal universe with the huge black/white hole in its centre?

  • Philip Murphy
    Philip Murphy 2 months ago +5

    Being early to a PBS Space Time Clip-Share video is great, Quality content is always worth a watch.

  • J
    J 2 months ago

    This is your best episode. And that’s saying a lot.

  • Shieldshocker WoT
    Shieldshocker WoT 2 months ago

    2:24 This question itself and the answer is the best thing for me in this video, I'm so happy I found you :D