PBS Space Time
PBS Space Time
PBS Space Time

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.

Venus May Have Life!
Mapping the Multiverse
Are Axions Dark Matter?
The Doomsday Argument
Is The Universe Finite?
Is Pluto a Planet?
  1. wulphstein

    wulphstein3 hours ago

    The physics community needs to hire "common sense analysts" to try to make sense out of what is really happening with real physics. Get rid of these dumb interpretations like MWI, banging branes, quantum loop gravity. You should really look around for "new" phenomena!

  2. wulphstein

    wulphstein3 hours ago

    The other problem with today's physics is that you have conflicting ideologies. Michelson-Morley claims there is no medium; simultaneously, there is a Higgs field, other particle fields, gravity fields, Casimir fields, and all of these fields seem to be bound by the invariance of the speed of light. How can "superstrings" be fundamental when they don't even explain what spacetime is made of? Not to mention that superstrings unify QM with GR, but not big bang cosmology!!!

  3. wulphstein

    wulphstein4 hours ago

    Vibrating superstrings are not compatible with big bang cosmology.

  4. Luke R.

    Luke R.4 hours ago

    Isn't it possible that quantum information is lost when the theoretical mass decay happens?

  5. Wiltu Wiltu

    Wiltu Wiltu4 hours ago

    Venus does not have an atmosphere, how will that be possible?

  6. Eiya Domingo

    Eiya Domingo4 hours ago

    It just works

  7. wulphstein

    wulphstein4 hours ago

    Boring topic! Why don't you address UFO physics?

  8. wulphstein

    wulphstein4 hours ago

    Any science-fantasy video that doesn't address how UFO physics might be possible, is just a waste of time/effort/video. If so many people claim to see UFO's, maybe you should listen to their stories. There is so much potential new physics that might be possible, including plasma fields, passing through water and air without resistance, hovering, why do UFO's seem to rotate? Why can UFO's make right angle turns? Honesty, these physics topics are less interesting than what alien civilizations seem to really be doing to human observers.

  9. Nico Coetzee

    Nico Coetzee4 hours ago

    Can we please try the B-side of 2020?

  10. Adan Phu

    Adan Phu4 hours ago

    To have 2 dimensions, you need to have something coming out of the line. As for 3 dimensions, you need to have something coming out of the plane. Since that is the case, to create 4 dimensions, it must be out of 3 dimensions

  11. Adan Phu

    Adan Phu4 hours ago

    Is there just more than just space, time, and matter?

  12. Adan Phu

    Adan Phu4 hours ago

    Just like a bacteria wondering about the edge of my feet (:

  13. Adan Phu

    Adan Phu4 hours ago

    We are so small comparing to the universe yet we already traveled to the edge of our universe in our mind..

  14. The Power Lover

    The Power Lover4 hours ago

    *Consciousness does not emerge from the "physical reality", the "physical reality" emerges from the "consciousness".* *That was scientifically "proven" by the US Army, at least since, the 80's (evidence in documents declassified by the CIA, and published directly by it, on its own official website, at least until now October 26 2020)...* *Despite of not being the best theory and therefore model (even exist the not low possibility of that the CIA is skewing it),* *the theory of Thomas W. Campbell, a nuclear physicist, is the best public, and scientific, theory of everything.* *For those who thinks that Thomas Campbell is a scammer, I inform that despite the tiny funds (relatively to other public scientific projects like CERN) and the pandemic, at the moment of publication of this comment,* *he and his team are performing public experiments to "falsify" his theory (not to proven it, that isn't scientific!).* *Please give like to this comment in order to make Matt O'Dowd read it!* *I'm pretty sure that, unfortunately, Matt will reject that theory, not because it's necessarily "wronger" than the currents public scientific theories, but because is too different than his curren scientific knowledge; and probably and sadlier, is opposite to his metaphysics (understanding metaphysic as the beliefs in what his knowledge about physics is based and frame worked).* *He's, like us, just a human, even he being a doctor in physics, a "scientist", he is first a human before a scientist, that is true to every human, NO MATTER HOW MUCH STUDY, NO MATTER HOW MUCH SCIENCE IT DOES! WE FIRST ARE HUMANS, WITH ALL THE BIASES THAT WHAT IMPLIES!* *(I´m just a Chilean zoomer, I am not even know Thomas Campbell directly, nor people that directly knows him, I'm also not part of the "Center for the Unification of Science And Consciousness" nor a person paid to promote his ideas, I even critique his theory and model in the second paragraph of this comment, and I personally disagree, with, for examples, his acceptance of the "individual" and derivates concepts (like "collective"), and his beliefs in the "free will" like a "actually real" thing).*

  15. Adan Phu

    Adan Phu5 hours ago

    When I was in college, I thought if atoms are made of protons and electrons. If we keep on thinking deeper and deeper, what makes the smallest matter that makes the particle.. I believe everything in this world is made of light (: Since matters keep on getting smaller and smaller when we think what are the smaller smaller and smaller matters made of (:

  16. guar67

    guar675 hours ago

    Wow, that's an interesting idea. Let's see... What if there are invisible unicorns in Antartica?

  17. Adan Phu

    Adan Phu5 hours ago

    I like PBS 😊

  18. erik zetterberg

    erik zetterberg5 hours ago

    Thanks to Matt and the PBS space time team for making these great videos! This time, however I find the argument at 6:50 unconvincing. The claim that the event at the bird would collapse the future of the event at the human does not seem to me to be supported within SR. Just because the human sees the cat event as simultaneous and the cat sees the bird event as simultaneous does not imply that any of the observers see the human event and the bird event as simultanous. Actually, the human, the cat and the bird would all agree that the bird event happens after the human event, and because of this the bird event could not collapse the human's light cone. In fact, there could be no observer moving at the speed of light or slower that would see the bird event as simultaneous with the human event, since these events are time like separated. The human's event and the human's future would remain uncollapsed from any observers view. At least as far as I understand SR. Please comment if there is anything wrong with my line of reasoning, so that I could understand the argument in the video,

  19. Adan Phu

    Adan Phu5 hours ago

    Is life really real? I think all of this is not real.. It’s like you are just watching a movie :)

  20. Adan Phu

    Adan Phu5 hours ago

    I always thought when I was about 14 that there are an infinite instants of past still existing but we just have no access to it. Since there is an infinite instants in a second..

  21. Adan Phu

    Adan Phu5 hours ago

    Discovering the possibility of traveling to the past is like Isaac Newton just discovered the apple fell to the ground is just gravity 😚😝😝😬

  22. Adan Phu

    Adan Phu5 hours ago

    I always wondered when I was young, where did the past go. There did just less than millisecond ago go?

  23. Adan Phu

    Adan Phu5 hours ago

    It’s a good idea that the US has one website to share all their discoveries 😊

  24. John Z

    John Z5 hours ago

    This is one of my favorite channels along with Atheist Experience. I come here to relax my brain after watching religious nuts argue for supernatural. Their lives and problems seem so mundane and insignificant compared to the mysteries of universe.

  25. non-matter pro

    non-matter pro5 hours ago


  26. Sagittarius A *

    Sagittarius A *5 hours ago

    What!?! I do?

  27. George Salles

    George Salles6 hours ago

    The rick and morty reference at the end, very nice hahah

  28. Edward Smith

    Edward Smith6 hours ago

    The Vulcan Science Directorate has determined that time travel is not possible.

  29. Jim Mooney

    Jim Mooney6 hours ago

    I live in Arizona. Bring it on!

  30. Jimmy R

    Jimmy R6 hours ago

    If free will is real, then it's caused by intelligence. But just as much quantum mechanics occurs in inanimate objects, so quantum mechanics cannot explain free will.

  31. E L

    E L6 hours ago

    I think I'll borrow that salute.

  32. Simranjyot Gill

    Simranjyot Gill6 hours ago

    Anyone aware of the tool being used to make such awesome videos.

  33. Matt Schellenberg

    Matt Schellenberg6 hours ago

    Kind of a WSOGMM then? It's all about perspective.

  34. jemborg

    jemborg6 hours ago

    Sound processing in the brain 🧠 is delayed to match visual processing... so, yeah, proof we live in the past, slightly.

  35. mouthpiece200

    mouthpiece2006 hours ago

    A lot of smart minds in here I'm sure. Anyone read "The Oracle, The Jubilean Mysteries"? Its a prophecy book about Israel. Can anyone confirm it or debunk it? I believe its true but interested in the commentary of any intelligent person. Or if you've read The Harbinger Books.

  36. Eric Malmstrom

    Eric Malmstrom7 hours ago

    I have been watching for years, this is ABSOLUTELY the best written and delivered episode. The graphics were great, but the writing and delivery were amazing! Thanks, Matt!

  37. Craig E.

    Craig E.7 hours ago

    Rick and Morty. Love it.

  38. Craig E.

    Craig E.7 hours ago

    So block universe. Got it. My daughter will be thrilled when i tell her we are living in Minecraft.

  39. Gabe Anderson

    Gabe Anderson7 hours ago

    Plot twist: The Bohr and Einstein theories are entangled. If you try to test one, you affect the validity of the other. 🤯

  40. Jesse Valentine Portz

    Jesse Valentine Portz7 hours ago

    Time is the space where opportunity lives now. Time is the dimension of causality. Time exists as a fluid membrane to allow energy to propagate.

  41. wulphstein

    wulphstein7 hours ago

    So a guiding equation is too un-parsimonious, but infinite number of universes is okay...

  42. internet writer

    internet writer7 hours ago


  43. Lucas Bernard

    Lucas Bernard8 hours ago

    joe from impractical jokers was "tuvixed" with the micro machines guy

  44. Troy Mosher

    Troy Mosher8 hours ago

    Dudes like the Jim Morrison of science. I can't follow half of what he's saying but it always trips me out.

  45. Ahmad Fodeh

    Ahmad Fodeh8 hours ago

    can you please provide where do you get those thumbnail images from ?

  46. Norm Johnson

    Norm Johnson8 hours ago

    Speaking as though there is more than one universe is pretty comical. Do we have any evidence of that at all?

  47. Garry Coates

    Garry Coates8 hours ago

    This is an evidence free opinion better called clickbait

  48. Midori Sato

    Midori Sato9 hours ago

    The future is determined by our choices, and our choices are determined by the future. It's a false dichotomy, as there's no difference between the two.

  49. youreallbrainwashed

    youreallbrainwashed9 hours ago

    Oh.. smart people language. Damn ☹️

  50. Doug Crawford

    Doug Crawford9 hours ago

    Is this guy speaking English?

  51. Jrod'sTech Irvan

    Jrod'sTech Irvan9 hours ago

    I don't think you'll see this but my question is. To begin this query, let's imagine we've survived the collapse of our star somehow. It's now a white dwarf we still can't star travel because that wasn't possible. I know allot of supposes. Anyway Mercury becomes our last bastion of life. Now we're closer to our host star surviving somehow seeing how Mercury survived being swallowed by the star and the blast. Because of the gravity do we experience time slower than before because gravity is higher? Or does a white dwarf have enough gravity to do that. Or is it the same or less because the mass is basically the same if the sun?

  52. Zarah Andrahilde

    Zarah Andrahilde9 hours ago

    What a beautiful use for all that iron compared to tanks. What a thought.

  53. smokey04200420

    smokey042004209 hours ago

    A year has passed and you should have posted the address 4 days ago. But you didn’t. That’s why no one showed up.

  54. wulphstein

    wulphstein9 hours ago

    We all know that the theoretical physics community is hopelessly lost. First, they assumed that a “luminiferous aether” doesn’t exist; they didn’t try to figure out some other way to construct a speed of light invariant field; and they’ve been stuck for about a hundred years. Second, they are hyperfocused on superstrings and quantum loop gravity. The problem with those theories is that vibrating strings and wiggling loops don’t behave like the big bang. Have you ever sat down to eat spaghetti, and it exploded? What about a bowl of cheerios? No? Me neither. The argument for a prime graviton G’ or first photon comes from the Arrow of Time concept of the big bang. The forward direction of time is always to increasing entropy. That means the reverse direction of time will decrease entropy across the whole system. In the case of the big bang, there is no reason for there not to be some minimum entropy caused by some phenomena of banging branes or whatever skeptical theorists think caused the universe. But the graviton is postulated to be the fundamental particle. If so, then why not let the prime graviton carry the burden of the energy content of the entire universe. A single photon on the surface that has energy 1070 joules would have a frequency of 10104 Hz. At that frequency, one cycle would occur in a time of 10-104 seconds (the smallest unit of time). The larger the volume of space that this energy could exist in, the higher the entropy. I would therefore argue that for a big bang of energy content 1070 joules, the absolute possible minimum entropy would have to be a single photon inside of a volume with a diameter equal to the wavelength of that same photon. Given c=\lambda f, the speed of light equals the wavelength times the frequency, the wavelength is about 10-96 meters which is much smaller than the Planck length. For a volume of V\ =\ \frac{4}{3}\piR^3, we are talking about the energy of the big bang inside of a volume of 10-288m3, the smallest possible volume. What smaller state of entropy could there ever be? To summarize, why do we need an expanding graviton anyway? Answer: superstring theory and quantum loop graviton explain the connection between quantum mechanics and general relativity. In contrast, the expanding graviton will explain quantum mechanics, general relativity and big bang cosmology. It does so by including expansion into the graviton. String theory and QLG do not address expansion. What do “expanding gravitons” have to do with experimental and empirical physics? Expanding gravitons are everywhere, even if they’re not expanding. You can use a crystal to quantum entangle photons. The connection between the entangled photons is identically, a graviton. Any time you calculate the wave function solution to a quantum mechanics problem, you are writing a mathematical equation that is describing gravitons. Wavefunctions are the mathematical description of gravitons. When gravitons expand from a point, at the speed of light, they inevitably collide with subatomic particles. Those gravitons become The idea of an expanding graviton is that it replaces superstrings and quantum loops with a “particle-space” that expands from a point, every point in space, where an event occurs. It expands at the speed of light like ripples on a pond.

  55. Jocelyn Joseph

    Jocelyn Joseph9 hours ago

    Great presentation.

  56. Jocelyn Joseph

    Jocelyn Joseph9 hours ago

    In natural events in physics, vacuum is present at the point where two convex (positive fields) collide as in linear force with oscillation or where a concave (graviton) ring forms.

  57. tiqvahone

    tiqvahone9 hours ago

    The only part of this space time lesson I understood was "we're out of time". My question is why? Just dilate it.

  58. tiqvahone

    tiqvahone9 hours ago

    I wonder.... Did Matt's mom ever tell him he thinks tooo much?

  59. Blue Dress

    Blue Dress9 hours ago

    The speed of light is irrelevant. Everything that Einstein claims will happen will never happen because we are incapable of making it happen. So are his claims correct. If you really want them to be then they will be, how's that for relativity.

  60. tiqvahone

    tiqvahone9 hours ago

    Lost me at 6:45 "any part of spacetime not in your future light cone could potentially be in the past for another observer in your present etc.... " . Had to rewind the light cone.

  61. John Smith

    John Smith9 hours ago

    Philosophically I feel that there is no past or future. Time probably isn't what we think it is. Time is just an illusion we created because it feels like we are moving forward and we know that a "past" existed. Our intuition created time.

  62. Mark Shiman

    Mark Shiman9 hours ago

    I have a masters in physics, and still struggle with this concept even after rewatching a few times. Why are we basing our present reality only on what we currently observe? We know the speed of light. So if we observe something distant with our telescopes, we know that it occurred very much in the past. If we know our relative speed to the event, we can calculate exactly when and where it happened. This is true for all observations. If ever observer did this regardless of where they are in the universe, we would all agree on the same "present." There's no need to claim stuff in the future is in someone else's present 6:49. That's simply only true if we mistakenly believe things that we observe are currently happening either for us or for any other observer with their own observations. Seems like people are scratching their heads when there's a simple solution, which is just understanding that light takes time to travel. Observations take time. A lot of this seems like total nonsense (you are the only being, many worlds interpretation, collapsing "cone" of future) and it's awkward listening to it from such a reputable channel. No, my "now" isn't part of someone else's past or future if they simply know light works. I wanna talk to Matt himself, but it's $100 a month to get in contact!!

  63. Mark Shiman

    Mark Shiman10 hours ago

    It took me a few watches to understand, but the video get's wonky around 8:00. Why is what's present only based on what you are currently observing? If we observe a super nova and know how far it is, we know how distant in the past it exists. We know that it didn't happen "now," we would know exactly when it happened and where. If everyone agreed to calculate the relative distance and speed of the objects distant they're observing, we would all agree on the same exact now-slice. This would be the same no matter how far away or fast traveling the other observers are.

  64. HELL WITH IT!! B. L. A.

    HELL WITH IT!! B. L. A.10 hours ago

    Unified field theory?

  65. José S.

    José S.10 hours ago

    There is no universe. All we got are: information, emission, reflection and receptor.

  66. Eddie Papi 2015

    Eddie Papi 201510 hours ago

    So the Mandela effect is just the illuminati scientists doing experiments?

  67. Trent Michael

    Trent Michael10 hours ago

    This video was updated 6 days ago, but many of the comments are reported as being made a week ago. USlikes's awareness is smeared out over hours.

  68. BumbleBee Productions

    BumbleBee Productions10 hours ago

    Yes our future is predetermined... BUT NOT fixed... AND to change your present needs a LOT of energy to move what was predetermined from the beginning...

  69. Akm58

    Akm5810 hours ago

    Considering the sun might one day become a red giant, why go closer rather than further? Mars all the way!

  70. Herbert Miller

    Herbert Miller10 hours ago

    16:10 Matt don't worry help is on the way

  71. One Million Dead Koalas

    One Million Dead Koalas10 hours ago

    I thought it was like a pc. Someone pressed an on switch and its been booting up and installing core system files ever since.

  72. Strable Fable

    Strable Fable10 hours ago

    “Image the sun is a perfect sphere” Representation os the sun: covid-19

  73. Eric Eisenstein

    Eric Eisenstein11 hours ago

    Hi PBS, here is a de-classified official NSA document from 2004. It’s a technical journal outlining 29 messages received and de-coded from extraterrestrial origins in deep space. www.nsa.gov/Portals/70/documents/news-features/declassified-documents/ufo/key_to_et_messages.pdf Good luck! Truth is out there! 📏🌐⚪️📐🛸✨⚪️⚪️

  74. Ga Wa

    Ga Wa11 hours ago

    Let's look at the mathS. MathSSSS. Thank you.

  75. Cynthia May

    Cynthia May11 hours ago

    Without meaning to sound hyperbolic, I suspect that was the most facetious ending to a video ever. Bravo, Cheers! ;) Well, if time doesn't really exist then maybe I am being overly hyperbolic...Hmmmm... Future, Past and Present do not exist, only the multiverse at the quantum level. They all exist together as one wave rippling giving way to the space/time illusion that provides the course of entropy. All space/time, now, then, there, was, & what will become is just the same as the space left behind between two pizza slices. The illusion is that there are two slices but the truth is that it's a pizza even if it's sliced, diced or chop suey-ed. The basic fundamental laws (pizza) never change through entropy, concluding that ALL is ONE and it's and not separated by time/space entropy. This concludes there is but one dot expressing itself in unlimited possibilities that the course of entropic expression will allow with constraints of physics law.

  76. wulphstein

    wulphstein11 hours ago

    I just don't understand how super-strings or quantum loop gravity is compatible with big bang theory.

  77. Ashwini Raghuwanshi

    Ashwini Raghuwanshi12 hours ago

    Only part i understood is his thanks to patereon followers

  78. Samm Salvey

    Samm Salvey12 hours ago

    2:45 _At 50km altitude, the temperature and pressure are close to earth's_ . I hope he means the pressure and temperature of venus at 50km is similar to earth's, only for pressure at surface, and temperature at surface. The atmosphere overall would have to be hella thick to be similar to earth's surface pressure at 50km. We can't even breathe at 50km up. Most people would probably think they are in outer space at 50k, the atmosphere is so thin.

  79. adarsh vanjari

    adarsh vanjari12 hours ago

    Couldn't understand

  80. Michael

    Michael12 hours ago

    If the universe is deterministic, does that mean any one particle contains an infinite amount of information regarding all of its future states? If so I would think it would take an infinite amount of energy to calculate the future of one particle. It seems like from a practice perspective the universe isn't actually deterministic.