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.

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  1. author

    AudioAndroidIl y a jour

    What is you had the Video Recorder pointed at a reflective surface like a Mirror and have the mirror observing the photons as they enter the slits, will we still get the same result?

  2. author

    DavidIl y a jour

    I don’t think so, axioms are things they have in maths

  3. author

    James BrabyIl y a jour

    On no! The evil carbon soccer ball is coming to get me

  4. author

    lasso atrainIl y a jour

    No light if caught in a field and and can no longer travel the speed of light then can no longer be considered light . The property of light says light travels 186,000 miles a second in a vacume, if it doesn't then it must be something else .what was it before it became light ? Simple energy, potential energy .I think anything can be light if accelerated to the speed of light. Perhaps if trapped in a field it can not release it's energy as heat because there is nothing to transfer it too so it precipitates out as some type of particle .Perhaps dark matter .Perhaps as the elements it was before being accelarated, perhaps that's why the elements can be known within a star by analyzing its light or by slowing it below the speed of light in a field.

  5. author

    Awesome CitizenIl y a jour

    You're explanation already made my head go bang pal.

  6. author

    diggooIl y a jour

    Sorry bro, time doesnt exist

  7. author

    кιℓℓυʍιηαтιIl y a jour

    This kind of infinity is very beautiful if you try to really imagine what it means

  8. author

    Yonlay QuindemilIl y a jour

    I cannot help but seeing a brute force in all this kind of explanations. At the end it is like that because that is the way it is. The Planck constant just happens to be. Maybe that is the reason why it was discovered by chance. At the end, at this time the only we can say is that if we get lower of the Planck length we get a black whole and that is, everything destroyed.

  9. author

    David MartinsenIl y a jour

    Whether its global warming or ice age, we dont have to worry about it 4 500yrs ..

  10. author

    PearcePlaysandvlogsIl y a jour

    we eat it

  11. author

    Tony BarreraIl y a jour

    Nice that axions are found we had already predicted their existence.

  12. author

    berkoYTIl y a jour

    braib cramp whoaaa

  13. author

    arun tejIl y a jour

    Infinite versions of me .. And I am the smartest .!😎🤘😂

  14. author

    ThetinebrokenIl y a jour

    What you are searching for is called Creation

  15. author

    George SchlalineIl y a jour

    Dark Matter 2525 will be judged mate

  16. author

    ThetinebrokenIl y a jour

    And he wears a 10 dollar tee shirt

  17. author

    Someone SomeoneIl y a jour

    Let's Programm a blackhole with binary energy inputs to get a microverse out of it with a spaceshuttle and blackhole generator etc. inside and make a nearly infinity spread. Also let's look on fluctuating quarks and the possibility to connect and sync tinier quarkstructures to reach also paralleluniverses.

  18. author

    ThetinebrokenIl y a jour

    A grain of sand.. ya . ..why not smaller?

  19. author

    frazler OfficialIl y a jour

    Those blasts from the sun can melt the side off a planet completely and Make it a semi-sphere if the planet is close enough to the star

  20. author

    Little MonkIl y a jour

    He says watch as many videos as you can to absorb them through osmosis because this subject is unintuitive and hard to grasp, and then he tries to teach this extremely difficult subject speaking at 10 miles an hour.

  21. author

    frazler OfficialIl y a jour

    My opinion: Mars was once like earths climate lots and lots of years ago, I don’t know how many though

  22. author

    Angel WhiteIl y a jour

    If energy is made up with a plus and negative could this be what is making the expansion of space and time.... This dark matter... All rotation of the galaxy's all the energy.......

  23. author

    Vivek JoshiIl y a jour

    "Axion Detergent"...Scientists are funny.

  24. author

    Rob PerryIl y a jour

    Big Bang theory holds that the universe must have limits in order to allow for expansion.

  25. author

    Hans MolemanIl y a jour

    *Why would we need to assume the simulation of past lives at all?* I feel you brushed off this point as it was initially made by NDT - past inconsistencies can be written off as delusions, miracles, what have you. Ergo, one simulation needed with pre-programmed starting case.

  26. author

    NachannachleIl y a jour

    Before terraforming Mars, let's think about efficient ways to terraform Earth first. As young kids like to slogan nowadays: "There is no Planet B.".

  27. author

    Hans MolemanIl y a jour

    Every time I hear _'finely tuned'_ , I want to ask, _'May I see the knobs?'_

  28. author

    5pecularIl y a jour

    ... were it not that I had bad dreams.

  29. author

    david WilliamsIl y a jour

    Maby theirs so many axioms that arnt moving that they stop eachother and cant travel

  30. author

    hiIl y a jour

    So this means the real question is who's coming for us first. Evil Morty or Snowball?

  31. author

    goawaygoogleIl y a jour

    dem sweet burns

  32. author

    5pecularIl y a jour

    10^10^90 is a piece of cake, mmmm cake. In some other iteration of the universe I am eating cake, mmmm.

  33. author

    Vythe1andonlyIl y a jour

    universe: Scientists: but y tho

  34. author

    5pecularIl y a jour

    Are Matts hands faster than light? or is it just me?

  35. author

    Ged WoodsIl y a jour

    They forgot the ending. When our star turns into a black hole

  36. author

    mnELLIl y a jour

    Can your sound guy mix all the audio levels to the same db on each episode....hes disturbing my sleep.

  37. author

    Houdnzik SekačkeIl y a jour

    So, would axions allow invisibility? Would the photons go 'through' the wall unaltered?

  38. author

    Stirling NewberryIl y a jour

    This is obvious and was the way I was taught, including lake tides, It was in a grade school book on the moon.

  39. author

    awebmateIl y a jour

    The Big Bang was the creation of a black hole and the universe is not expanding, we are shrinking, forever speeding up towards an unreachable shrinking center.

  40. author

    cherubin7thIl y a jour

    Is there a theoretical lower limit how weak the interactions could be?

  41. author

    J. KincaidIl y a jour

    would have been interesting if not prohibitively expensive and difficult, just to go and check it out.

  42. author

    Kaleb HengIl y a jour

    Bruh you would look like lord Farquad with out the beard

  43. author

    Jø KərrIl y a jour

    His answer to the last question, the "so what" question, was so great. I love when people are like "who cares about (insert scientific discovery here), it doesn't impact me in "the real world,"" when all scientific discoveries end up opening doors to other discoveries, that end up leading to others, which end up making smart phones possible, for example. I'm looking at you, quantum physics lol, you have my gratitude. All scientific discoveries matter in the grand scheme of human understanding, but if you only care about what it can do for you, then chill, the discoveries trickle down to material things, such as smartphones, as I previously stated. Can you imagine not having your smartphone? Well thanks to our discoveries in the field of quantum physics, smartphones are now a thing.

  44. author

    trf12567Il y a jour

    Whoa... Wait a minute. What do you mean a person doesn't pop in and out of existence when they cover their face? Next you'll be telling us Santa Claus isn't real

  45. author

    Ed KeosadaIl y a jour

    Time started when we began keeping a record. Easy. Next question.

  46. author

    TIMOTHY L ChristiansIl y a jour

    They still don't know , they where not there!

  47. author

    MabDarogan2Il y a jour

    I commented on the chimpanzee. Were you too lazy to check?

  48. author

    Ann Dee RoidIl y a jour

    Could dark matter just be the sum of the virtual particals

  49. author

    Isys EyeIl y a jour


  50. author

    theonlytrue8tIl y a jour

    When I watch PBS SpaceTime on Valentines Day and am sleep deprived, I Write stuff like this: -Quantum Love 0- -Time... to travel „You are not here!“ says the voice from the Navigation tool, while marking my position with an X. „Typical...“ I sigh so loud my ears might start bleeding. So neither there I am... Just lost in a time between the spaces. Remembered only by future dreamers long forgotten. They look like you and I, in the Review mirror of my Not-Delorian. Dancing in the Starlight, that in the end might just have been an incoming truck. I curse causality for making time as it always has been. No chance for us pushing further to go back and help you against whatever came your way. Fixing your past before you would have known that it would break. So you would not be scarred by the sharp edges. Even if this means making me obsolete in your life. A footnote in the diary you then never could have written. At least like this, I could sleep in knowledge of you never having loved me to begin with, a price that's worth to carry with me. Alas... not even my mind belongs to me. So how could I change the past by going forward on this path of shattered chances? How much I ever wished your tears would flow backwards, to turn your frown upside down. It was never meant to be. My rage without a target to hit. Nothing to kill but time itself. This goal is just unreachable, like a Star that explodes backwards in Time. So vast and simply... impossible. I cannot accept these facts and keep fighting against a past where I am, Not as now I will never be... ...and you not even known to me. Still: I'd burn a Galaxy to keep your pain away. to never let it happen again for a first time. But as all of us: You cannot stop to run. Because time always just falls in step with you. Might as well make the best of it while the metronome keeps ticking. My heart beats 32768 times a second. So by all that it has done, my heart should be; with all the rights of Mass/Matter conversion, just be stone. Your presence softens it a bit. By bit, by bit, by bit. Trying to change the past is a goal just made for fools and errors. To shape the future by the Actions in the now is a task for heroes. With a sense of wonder, how you ever got so strong. Not wanting for the past to change at all. Just packing your Backpack on your back to never look back. I focus my Rearwardview on my Backtracking Machine.Put it from driving backwards once more and never, into reverse to return from the past into the now. To see my yet. And all that is; still, not done in it. 88 miles per Hour into my here, seems so slow compared to you. Walking with confidence inside yourself, while I stumble between the strings of a past reality. No one knows what path you will choose, once a fork has been presented. Your lifepath is like, the most beautiful double slit experiment! But am I, with you entangled? Your Love, in some of the times. just a particle. Cannot touch it, to my dismay. Sometimes your love was, and may be, a wave sweeping me away. I do not mind. As long as you find laughter on your way.

  51. author

    Ann Dee RoidIl y a jour

    Sooo what errr how can something have "1/2" spin I'm an person who can picture and build with my "minds eye" but when I try to see this ... I'm at a loss and see something like 1/2 the wave sign of an alternating current

  52. author

    wx 40Il y a jour

    İs he french person?

  53. author

    wuffpawIl y a jour

    Can someone help me here? How can causality be preserved if the act of measurement effects the other particle instantaneously?! Doesn't that action still violate causality and the speed of light rule?

  54. author

    Lina UmpierreIl y a jour

    Androlactea Galaxy I call it!

  55. author

    Vint GuitarzIl y a jour

    Why is this guys HEAD SO BIG compared to his body?

  56. author

    wuffpawIl y a jour

    This one really verged on the metaphysical

  57. author

    ForTaxReasonsIl y a jour

    Me before starting this video: I dont entirely understand string theory Me after this video: _string theory is right_

  58. author

    ForTaxReasonsIl y a jour

    Me before this video: i don't entirely understand what string theory is Me after this video: _string theory is wrong_

  59. author

    guru dutt sharmaIl y a jour

    How can i unsee his nostrills

  60. author

    Archana YadavIl y a jour

    Actually Albert Einstein discovered gravity truly

  61. author

    J BirdIl y a jour


  62. author

    spim randsleyIl y a jour

    I woulda said something about the monkey/chimp duality, but you had your hands full with the Principia thing.

  63. author

    PJ BrokeIl y a jour

    We’ve found an exploit in the universe where if you can hold the entire universe within the universe, you can essentially become a god tier level race within just a few million years, Considering you could simulate consciousness. Hello quantum!

  64. author

    Rafael RodriguezIl y a jour

    Alcubierre... That is a Mexican, Spanish last name. The last letter "e" is not silent and he is not French. Al-ku-beer-re

  65. author

    Donovan SteadmanIl y a jour

    My question is this...seing that Venus has basically the same gravity as earth...doesnt that mean that who ever goes there is basically stuck with no hope of return? I mean wouldnt they need Giant rocket boosters and a launch pad just like we do on earth to go to space?.how would they build that on venus? On mars the gravity is weak so we wouldnt need rocket boosters to pack up and come home if something goes worng.

  66. author

    You Got Beat By What?Il y a jour

    "Thats not how science works." Meanwhile everyone is accepting gravity hmmmm.

  67. author

    Mike BurnsIl y a jour

    You need a.i to settle mars

  68. author

    real a'fIl y a jour

    Why is this dude so dusty?

  69. author

    Row BeeIl y a jour

    0+0 is not =1,,i think if scientist not believe if that 0 is exist,it means that 0+0 can be =1

  70. author

    Adam FreemanIl y a jour

    @5:58 is no one going to mention that time dilation doesn't make the trip seem shorter from the astronaut's perspective?

  71. author

    Darth QuantumIl y a jour

    Unfortunately, string theory is wrong. ST was discovered accidentally back in the 70s. For so it's been around for 50 years and has yet a mke a single testable prediction. By that I mean an experiment we could perform right now in a lab. Initially ST had 26 dimensions and contained only bosonic particles, no fermions. That clearly doesn't describe this universe. Eventually the dimensionality was whittled down to 11. So where are the extra dimensions? Why don't we see them? Well, the answer supplied by the string theorists is that they're tiny - basically existing at the Planck scale ( about 10^-35 m). Besides being an obvious dodge, this fails to explain why 4 dimensions are "large" - why did only 4 dimensions inflate at the Big Bang and not the other 7? Maybe the other dimensions forgot to eat their Wheaties :) Another problem is supersymmetry - the LHC has produced no supersymmetric counterparts to the particles we actually observe. For instance, there should be a "selectron" , a particle with the same mass and charge as an electron but with integer spin (i.e., a boson). Well, where are they? The LHC can produce center-of-mass energies on the TeV scale, which is about 2 million times the rest-mass energy of a single electron. If selectrons existed , they surely would have been found by now. So we can rule out superstring theory as a viable model. The poster Leon Martins is correct - as Feynman rightly stated, no matter how smart you are, if your theory doesn't agree with experiment, then it's wrong. Some argue string theory is mathematically beautiful and therefore must be right. Well, I would remind them that Kepler spent years trying to fit planetary orbits into the Platonic solids to no avail. Mathematical beauty alone doesn't guarantee one's theory will hold. Despite the name of his book, Brian Greene is mistaken - the universe isn't "elegant"; it's a messy place that apparently forgot to use supersymmetry and strings. Now, I'm sure my skepticism of ST will incur the wrath of a certain Czech string theorist who views the world from his particular "mottled" "reference frame" (if you read any physics blogs on the internet at all , you know to whom I'm referring) , but that's OK. At least I've never been fired, unlike some people :)

  72. author

    Mister HandIl y a jour

    Is gay sex in prison really gay? I ask as my brown hole has hairs.

  73. author

    Takumi [Valenoern]Il y a jour

    so, am i getting this right - axions basically explain how particles can appear to come from nothing, by being like another layer of temporary particles before virtual particles? If so what's the difference between axions and "particles more fundamental than others", is it that a photon is not broken apart into axions & axions just change to other particles because that's more stable? why does such a small change like that alter the physics of the particle so much (i always thought of quantum particles as being like chemical reactions so it made sense to me quarks could build nucleons with different physics, or even that two particles could "react" to form two others of the same 'size' if energy is conserved, but i'm confused why one axion would just become a photon, or i suppose 'where the energy went'.) could axion/vacuum mathematics maybe clear up what's going on with the double slit experiment??

  74. author

    Taunter AtwillIl y a jour

    No they're not dark matter, and neither do you matter! What is it with these uploads, are you obsessed or do you still need to created a life ? :-)

  75. author

    Alexander JamesIl y a jour

    Is it not more probable that Dark Matter is simply particles that operate and only exist in higher dimensionality? If Super Strings can operate within 11 dimensions is it not also possible for some particle to exist in the upper limit of this dimensionality, ergo only 4th, 5th, 6th dimensions respectively? These influences make sense, This gives them the "space" to move around matter that has a lower dimensionality then its own. It will also explain they interact and exert Gravity, because gravity is a connective quantum field, meaning it distorts space-time. Since they exisit in a higher energy state it is also possible that they have a higher 'relative' weight. Higher dimensional space can even be measured using amplituhedron and maybe to the extent of a higher dimensional particle. In my summation this new interconnected "set" of fields constitutes a "Realm". Where in the entirety of Existence is arranged into an 11th dimensional Torus (upper limit 12 dimentional). Where the 12th dimension constitutes the circumference or perimeter, if you will, of the torus. This structure even gives rise to the Saddle shape of space time. Well I hoped this helped :)

  76. author

    Nathaniel CoffinIl y a jour

    2:33 "several hundred kelvin" I am surviving that currently.

  77. author

    Émile vIl y a jour

    So if we destroy one electron we destroy the whole universe?

  78. author

    subliminalvibesIl y a jour

    Weak force < Strong Force < Axion Force? I theorise is that if Axions do exist that they're a stronger force than all others AND create anti-gravity. They could be responsible for the expansion of the universe!

  79. author

    varegabIl y a jour

    Thank you, Jesus.

  80. author

    Zahir khanIl y a jour

    This was a good episode .

  81. author

    SpeedingOffenceIl y a jour

    I didn't actually catch anything that conflicts with the notion that time started at the big bang beyond references to theories that you didn't elaborate on.

  82. author

    CogitoErgoCogitoSumIl y a jour

    So if you collide the electron with the positron you should destroy the universe.

  83. author

    Joshua GentryIl y a jour

    The General Theory of Relativity does not mention an infinite universe. In The Special or General Theory of Relativity book by Einstein, around the last chapter, Einstein states that his theory predicts the shape of the universe to be finite but unbounded. Not an infinite universe.

  84. author

    Charles AustinIl y a jour

    It's simple, really. Here is a thought experiment. Now, according to wave function, a particle exists in a superspostion state until it is observed by us. But....let's try this. pick an object in your room, like the bed, for instance. turn your back on it. Can't see it, right? Now, back up until you run into the bed, which, you will do. As soon as you hit the bed, you have to ask yourself, "I didn't observe the bed, per se, but it's there because my legs hit it. Are my legs the observer, and collapsed the wave function? Or, is the bed just part of object permanence?

  85. author

    colton PlayzIl y a jour

    Mars would be better for just visits but Venus would be better for long term... so I would rather go to Venus if we had the technology for a “cloud city”.

  86. author

    lampshade3123Il y a jour

    I want to know what would happen if we sent entangled particles into a black hole.

  87. author

    João da SilvaIl y a jour

    Axions are dark matter, and you can make it at home with a bosenosa explosion of rubidium superfluid haha

  88. author

    Big Al's ChannelIl y a jour

    I lost count of how many false, steeple hand gestures the bloke was insisting upon and was a total distraction from a very interesting topic. I would suggest just narrating in future, please.

  89. author

    Frederic MoresmauIl y a jour

    We know you starve me... Months till I can't do anything anymore then you say I'm toxic.....

  90. author

    Wayne WallaceIl y a jour

    What about underground cities on Mars? If you had 50-100m of surface rock/dirt above you, wouldn't that handle meteorites, radiation, and so forth?

  91. author

    SmailIl y a jour

    Just build a new planet from scratch

  92. author

    Robert PhillipsIl y a jour

    Query: When counting the mass of the universe, did they account for the variance caused by gravity? Einstein postulated that there is no experiment that tells the difference between gravity & an accelerating frame of reference. When an object accelerates, it gains mass ... relative to an inerial frame of reference (FoR). Since we are in an accelerating FoR, the adjustments to mass should swing both ways: particles that have been accelerated should have lower masses & particles undergoing greater acceleration should have more mass (at least as I understand the math).

  93. author

    Kaiser FrostIl y a jour

    Astronomy for millennials .

  94. author

    Jesse HaireIl y a jour

    Short answer:No Check SuspiciousObservers out for details

  95. author

    DavidIl y a jour

    It’s clear that our current understanding of math is not sufficient to explain nature. Just admit it. It’s because God made it all.

  96. author

    Patrick van der VeldenIl y a jour

    Could... Could we and the entire universe be inside a ridiculously large black hole?

  97. author

    General JellyRollIl y a jour

    Bill told me you can’t explain the tides

  98. author

    Joe CipollaIl y a jour

    Haha im no scientist but who are we to believe that our monkey brains know how the entirety of the universe works and say ZPE isn’t doable. Ive seen some little kid in a video power a light bulb with ZPE in a hime experiment. We find and new things about the universe all the time just look how far our science has come in 100 years. Instead of saying its not real or doesn’t have the power that is proposed without knowing lets fund experiments to find out!!!

  99. author

    Lucan KeyserIl y a jour

    Axions sound a lot like neutrinos. What’s the difference?

  100. author

    yogibear6363Il y a jour

    Whether it reaches top speed in an hour or a year is almost meaningless in a decades long project. Avoid the high acceleration pressure by accelerating it slowly for the first year. That alone could solve several engineering problems.