Space Time explores the outer reaches of space, the craziness of astrophysics, the possibilities of sci-fi, and anything else you can think of beyond Planet Earth with our astrophysicist host: Matthew O’Dowd.
Episodes released every Wednesday afternoon!
Matt O'Dowd spends his time studying the universe, especially really far-away things like quasars, super-massive black holes, and evolving galaxies. He uses telescopes in space to do it. Matt completed his Ph.D. at NASA's Space Telescope Science Institute, followed by work at the University of Melbourne and Columbia University. He's now a professor at the City University of New York's Lehman College and an Associate at the American Museum of Natural History's Hayden Planetarium.
Previous host Gabe Perez-Giz is an astrophysicist who studies black hole physics. He received his Ph.D. from Columbia University and also hosted PBS Infinite Series.

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  1. RedRocket4000

    Need to stay away from the false logic of this guy kept going despite experiments saying it wrong as a reason to go that way without sciantificly considering everyone who did that and who succeeded vs who failed the rest of their life chasing a beauty that was not going anywhere. In the Middle Ages they kept working at a form of mathematics that does not go any practical place other than creating a cool very complex game with multi level pieces.

  2. lasarith2

    1000x closer would put it at 46.5 Million light years distance, not exactly a singularity, he’s off by a factor of ^58 or ^59 .

  3. Lazarus The adventurer

    I understood this topic much easier when i watched the "Dark" series on Netflix!!!!

  4. Bruce Clements

    The fact that physicists feel compelled to inject unscientific terms like "great", "beautiful", "elegant", "profound", etc., when referring to SR and GR is due--to either some great or small extent--to the underlying tenuousness of Einstein's absolute dictum that everything (other than the speed of light, ironically) is relative. That is, the need to use emotional concepts to describe what is supposedly a physical phenomenon is evidence of an underlying insecurity about ideas and mathematics which might well be nothing other than "media hype" according to many, including Tesla to whom Einstein himself deferred when asked to name the world's greatest physicist. Further, a "theory of everything" which does not take into account "things" which science cannot touch and therefore cannot experiment upon--i.e., greatness, beauty, elegance, aesthetics, consciousness, etc.--would be misleading advertisement on its face, brazen "bait and switch" salesmanship to the core, and a most excellent example of cosmic "puffery" (read "lying").

  5. Neil Hopwood

    Anyone else see it as a bit of a crisis we have to resort to Many Worlds to build the most suitable version of the "present"?

  6. Simona Palosan

    Brilliant! I am watching all episodes now and I find them so exhilarating.

  7. Just Jean 0101


  8. Igor Volkov

    Dear PBS, it would really help if you could cover next time, why quantum physics is at all relevant in the macro world where we experience time and consciousness. It seems pretty obvious the future of a rock in space is totally determenistic. Does the quantum uncertainty actually play that much of a role in what we humans call future? Thank you.

    1. Igor Volkov

      Determenism does not exclude practical inability to predict. Complex systems we can not practically predict do not need quantum mechanics to be explained.

  9. Tine Tannies

    When I saw "black hole" I thought this was a Cardi B video for WAP

  10. Vincent R

    Loving this new series on time!!

  11. Richard Garcia

    Also! “I think, therefore I am.” Why is that everyone’s go to for philosophical enlightenment? I’m tired of hearing it because it’s non-sensical and only reinforces the unsophisticated ideology that you are anything other then your thoughts. You don’t think! “YOU” CANT DO ANYTHING BECAUSE “YOU” DON’T EXIST! At least “you” don’t exist as anything other then everything else. It’s so simple and elegant, how is this not conceivable to people?

  12. Rick Astley

    I was doing well untill minute 6

  13. manosvince

    background song at @3:50 ?

  14. Richard Garcia

    Both ideologies about the “universe” being a stupid mechanism or being created are very wrong.

  15. Jack B

    No, and neither do Birds. Get over it.

  16. Richard Garcia

    With our Right hand we fight to understand and rationalize our existence but with our left hand we sabotage our ability to be aware of it. We humans have a sort of natural psychosis about ourselves.

  17. David López

    It is where the coronavenus came from.

  18. Richard Garcia

    For all of the religious people, I’ll explain it this way. God is so bored of being God, God spends all of eternity pretending not to be God.

  19. Going Home

    His legs are really bendy looking Look closely

  20. Richard Garcia

    As hard as it may be for you to accept, there is no Universe outside yourself. It’s inside you and you’re inside it. We exist like a Klein Bottle in relation to everything “else outside you.” In reality you can only say what you’re not, you can never really say what you are. There are many common sense ideas that give away the show, the only reason you can’t understand is insecurity. Fear, power, motive, desire, it can all be chocked up to; we really don’t want to know because ignorance is bliss.

  21. Marvin Edwards

    There is no block universe. The universe consists of objects in motion. The objects can only be in one place at one time. This account of determinism is an illusion.

  22. callejondorado

    There is a tendency to relate or even equalize mind with conciseness, that's fine with me; but think of this, people think that mind is an illusion created by the brain, I say no, that is wrong. Thoughts do really exists, wether concrete or abstract thoughts, they exist in a world not yet discovered, my conjecture is that they are in the dark mater realm, and that they can exists beyond the existence of the brain, and more than that they can exists without any brain at all (ghosts for instance) and that it is the conciseness part that influence or is required for the completion of the quantum measurement. There is a bast world yet to be discovered.

  23. JBOM9000

    If things that are farther away are also moving faster than closer objects, that must mean something is pulling them? Right? Why would things closer be moving slower? Why isn’t everything pushing out at the same speed? If things really came from a single point, a single Big Bang, then all things should be moving the same speed since it originated the same point, due to the same initial push out. If you know the answer just share it lol don’t insult. These feel like incredibly obvious questions

  24. Da Cosmos

    We all living The Truman show sponsored by "Space Time"

  25. Программист на колесе

    To actually prove it, you need to travel FTL and, as a result, go back in time, not show some diagrams. Travel back in time from photon perspective - is it the same as travelling back in time from earth perspective? If that paradox ship goes to the distant star and then back to earth, will it actually return to earth before its own launch? could not figure that out. All that time/space matter is too hard.

  26. zer0Bot

    Does the wavefunction really collapses when observed? How do we know this is true if there's no evidence?

  27. Da Cosmos

    imagine explaining this to a caveman, from the past

  28. Nephilim Glass

    Things as small as a molecule or a bacteria, if found on another planet are considered "life".....but here on earth(especially western civilization) a heartbeat isn't considered life.....f###ing weird, huh?

  29. callejondorado

    Nice analysis. Make me think of these few persons (mostly women) that can feel and even see (in their dreams mostly) what is going to happen. Usually they capture a single event and usually is not 100% clear, it is like they can feel the most probable collapsing of the all possible probabilistic paths. Others can see the past. You can even talk to them, in particular those that have been helping Police in USA to resolve difficult cases. They visions are not completely clear, and that could be related to to fussiness of the quantum world.

  30. mikesmovingimages

    Wow! What?!? lol! So the answer depends...on my favorite flavo(u)r of quantum theory. But is my interpretation itself determined by quantum mechanics? Is it really my own, or is it pre-determined? Maybe I interpret, then quantum mechanics throws out a reality, which I interpret, which throws out a subsequent reality, which I interpret...interpretations all the down?!

  31. drewbert83

    Think of alpha centauri. We observe it as it was 4 years ago. Things have happened there that we have no way of knowing. And so if the future already exists for alpha centauri, then it must also already exist for us. Eternalism confirmed.

  32. Adam Cartisano

    We’ll have plenty of time for time, another time, on SpaceTime. Out of every episode I've seen, this one got me the most. So well written!

  33. Mitch Gilbert

    When one accepts the absurdity of the universe, it becomes an adventure of discovery, rather than a rabbit hole of confusion. 🐇

  34. Geary Kunkel

    Prove that each layer represents a fixed time period for these core samples !

  35. Neal Willis

    Why does everyone seem to believe that if the future is already known by the universe, that it implies super-determinism and lack of free will? Two or more things can be real at the same time. So is it really that absurd to think that a "deterministic" universe has simply already calculated what we do with our free will?

    1. Neil Hopwood

      Finally someone notices lol.

  36. Derek

    If you press replay enough times time travelers will show up on the screen when he says now

  37. Tikti Laok

    the way you talk increases my anxiety.

  38. ChrisGeez

    Found this after watching Sabine Hossenfelder discussing this issue in an IAI video.

  39. Wally Wally

    So the reality is the light that we see isn't reality because it's all ready 8 minutes old and my conscious is under the illusion that we see reality, now the subconscious on the other hand just says the irony.

  40. Let’s take a walk

    Past and future exist, but the present does not.

  41. CUBETechie

    What about u238 in fast breeding reactors it can be used too

  42. Wally Wally

    Yep dark matter is a conductor.

  43. Wally Wally

    Only a prediction exists in this matter. Not accurate information.

  44. Vishal

    Time can't be experienced without consciousness

  45. 8brightside8

    So what is THE INFORMATION that falls into the black hole? Videos and articles state this but but do not elaborate - what type of information?

  46. The Physics of the Soul and God

    Funny thing is he just debunked his argument that the double slit experiment can be explained by interference by the detector. In this experiment it is clear that the detector is not the cause of the wave function collapse but rather knowledge is.

  47. dutchrjen

    "Now slices" are irrelevant. They do not say anything about the universe because we can ONLY see "now" in a single location. "Now slices" are just perception we have as a limited observer. We can map the entire universe onto a single preferred foliation perhaps that's the true "now." All except this one foliation could merely be perception. The universe could be a block or perhaps something else explains it. As an observer we are limited in what we have the ability to know.

  48. Alain borgrave

    Another interesting question for this channel : what IS consciousness ?

  49. Anders Öhlund

    If multiverse is correct. Would that be something like another dimension of the universe block?

  50. JesseMoshe

    There’s some vagueness about what we mean when we consider the interpretation of a “deterministic multiverse.” In case anyone is interested, this paper here offers some helpful clarity by entertaining an intriguing thought experiment:

  51. lt118436572


  52. Leah Brown

    I love watching these they are so cool.

  53. Layton

    Your now was pre-recorded

  54. Sylak

    I'm more in the presentism view. Althought as a none physicist, my opinon on this is useless :-). But to me, if you wanted ( in your slice of universe/time) travel to the past, you will have to reconstruct every single, smallest unit of reality to the quantum states there where in at the moment you wish to travel. Because it doesn't exist anymore. and since the furtur doesn't exist, you can't go to it, you could "build" it maybe. but changing every quantum states of a whole universe seem crazy. Since we know that GR and space/time are incomplete, I don,t think the whole worm hole to the past, exist. well not to the past of your slice/box of time, maybe to a difference point in time of a places where time flow slower of faster than your own "box". that exist at the same time as your present. all probably wrong, but I like the thought exercise, and whatever become real, I'll accept it from my physicist overlords.

  55. Lubomir Vlcek


  56. ak11230

    I did study about space and time is like V letter at some point space and time become unity . Nothing move expend no time ... Time stops.... After years of looking into times and space ? I know I don't know nothing .....Ak

  57. Lubomir Vlcek


  58. ValenHawk

    Would Entropy be the equivalent of the motor in the phonograph ?

  59. Sam Ferguson

    8:33 Shoutout to that guy who sees a dead cat come back to life.

  60. Lubomir Vlcek


  61. Paulo Gama

    Can u make a episode about the problems in the inflation theory?

  62. Al Garnier

    Existence is the culmination of expansion, opposition, harmonic entanglement and harmonic decay of fundamental electron fields. The fundamental fields of electrons expand exponentally due to the aligned polarity of their spin/charge. These expansion fields collide at their perimeters creating Higgs fields of opposed electrons with opposed spin/charge. These opposed electron pairs with opposed spin/charge entangle and annihilate into gravity's conserved energy and electromagnetic radiation. When a extra positron up quark is introduced with an entangled electron/positron pair, a proton is created through the harmonic resonance (strong force) of their entangled frequencies as the neucli of an atom. The positron carge of the proton attracts other electrons toward it but, only an equal number of orbital electrons as positrons within a neucli can occupy the atom's harmonic resonant field from the flow of attracted electrons. This flow of electrons drag other proton neucli with it condensing mass. The denser the proton mass, the stronger the flow of electron gravity within the thermodynamic Higgs field. The universe is an evolving perpetual motion machine. Consciousness is a byproduct of the electrons ability to store and retrieve the electromagnetic data of an atoms work product through quantum tunneling. Fundamental conscious in the universe is only supported by human patrony with little evidence for a fundamental nature. What would consciousness be aware of if materialism did not exist? Consciousness is emergent from the chemestry and entropy of biological matter and is replicated in computer technology, similar to electromagnetic radiation from the electron's workproduct output of atoms of bayronic matter. Memory can be stored and retreived through the properties of quantum tunneling within electromagnetc fields in silicon substrates, similar to micro-tubuals within neurons of the brain.

  63. Yuval Nehemia

    "We'll have time for time another time on spacetime." Goddamnit Matt.

  64. Marek Zalipski

    Did anyone calculate the probabilty of interactions here and take into account things such as the number of atoms in the universe, proton decay (theoretically possible), virtual particles, the interactions of forces, various theories of existence, development of the universe etc? Also, let's state the interval of time here to make it easier to calculate, from the beginning of the universe to the end of it, and set hawking radiation and the inevitable state of entropy as the end of the timeline in our theoretical calculation. How much stuff could be barely out of our sight in regards to the general theory of relativity and quantum physics? Regards. I originally wrote this in my native lanuguage and put it through google translate but my 16 year old sister helped me lol. (she may or may not be writing this bit :D, he complained quite a lot about me trying to finally get it right). Thoughts?

  65. Mike_o

    I need an explanation How would anyway have my future in their past? that would imply they have seen the actuall future stuff that never even happened, a.k.a they live in the same moment i do but at the future. with means they can "time travel" backwards, if they can't then they are not seeing my future they just seeing my past, that didn't happen for me yet. A.k.a if i travel in the speed of light, and go 10 years forward in 10 minutes. eveyone AGED 10 years, except me. it's not like they also experiences 10 minutes. and you just skipped a head. as you can't go backwards, with means, you have just skipped time. you had 0 impact on the future in this case.

  66. Al Garnier

    No! Random mutations and natural selection is still a process of natural evolution, not a process of conscious ignorance and human intervention.

  67. Bad Crab

    Matt did not mention, that after some time the series no longer approximates the field and diverges

  68. Attila Horvath

    I have a question. If I understood right the density of this interstellar debris field was calculated based on an Oumuamua like object flying near us every five years. This calculation looks flawed to me, we can not take the creation of the Pan Starrs as a data point and the next data point is Oumuamua. We only have one data point and the debris filed density can not be calculated in any way according to my understanding. What am I missing? Please help.

  69. Jesse

    I'm having trouble wrapping my head around this 'future observer' the cat can 'see', acting to collapse my future. Moving at light speed, the best a cat can do is approach along the diagonal of my past light cone - which is what all photons do! A photon emitted from outside of my past light cone will certainly reach my future self - *but it hasn't yet* and it can't interact with me until I get there. The waveform cannot reach that point until I do, pretty much by definition. So I don't know how we get to a diagram of a fast cat interacting with some other observer in my future before I do. From the photon's point of view, there is no time in the universe and all interactions are instantaneous, but that doesn't change the fact that that's *only* the photon's perception - it does still take time from the perspective of everything else, and it still can't interact with my future self *until* I get there.

  70. Yessin A

    Would a warpdrive work to pas through a wormhole? or would the gravity be too extreme for the warp drive to work properly to sustain above light speeds?

  71. Ronald V Ronca

    More nonsense from the scientific community to further impress upon the laymen their superior intellect. Listen to this man, he is explaining a possibility while trying to sound profound....there are theories upon theories constantly being's all possibilities, probabilities, theory and guesses. Only in time will we find the answers....but then what if time doesn't exist, in that case why bother, without time there is nothing.

  72. TheChunkylover79

    Thank You!

  73. Korpen

    A question about quantum entanglement If two photons are entangeled and and you measure the spin of one of them which would give you the spin of the other, isn't the information of the photon that was not measured just coded onto the one that was? This would mean that no law of causality was broken in the process of measuring which makes a lot more sense to my ignorant mind.

  74. George Clinton

    Do I understand correctly, that the present is the same to everyone, but the delay between the real present and our perception (which is to get the light travel to us from an event) causes that we don't agree on what's happened when? Or I didn't understand anything about this video?

  75. Jesse

    Given reality's apparent predilection for energy-efficient outcomes it's very hard to swallow the many worlds interpretation, which is about as energy *inefficient* as it is possible to be.

  76. Jesus Guevara

    Hey you guys are idiots time doesn't exist, time is just a concept that humans created in order measure how long something last. No other existence in the universe uses the measurement called time except humans.