Did Time Start at the Big Bang?

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PBS Space Time

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    Our universe started with the big bang. But only for the right definition of “our universe”. And of “started” for that matter. In fact, probably the Big Bang is nothing like what you were taught.
    A hundred years ago we discovered the beginning of the universe. Observations of the retreating galaxies by Edwin Hubble and Vesto Slipher, combined with Einstein’s then-brand-new general theory of relativity, revealed that our universe is expanding. And if we reverse that expansion far enough - mathematically, purely according to Einstein’s equations, it seems inevitable that all space and mass and energy should once have been compacted into an infinitesimally small point - a singularity. It’s often said that the universe started with this singularity, and the Big Bang is thought of as the explosive expansion that followed. And before the Big Bang singularity? Well, they say there was no “before”, because time and space simply didn’t exist. If you think you’ve managed to get your head around that bizarre notion then I have bad news. That picture is wrong. At least, according to pretty much every serious physicist who studies the subject. The good news is that the truth is way cooler, at least as far as we understand it.

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    سلطان الخليفي

    Am Vor 29 Tage


    1. Stefano Portoghesi

      How do we know that the Universe began 13.8 billions years ago ? Surely that measurement of earthly "Time" may be valid for our human sphere of reality only but what about universal "Time" , one individual's past event in "time" may be another individual' future event in "time" .

    2. Alex Bordon

      I have a new gravity, time and consciousness theory that connects quantum mechanics, black holes, dark energy and gravity with existence and a universal balance, what should I do?

      1. Alex Bordon

        Any tips?

    3. 420drwilldo

      If your really think about it what is time but the observation of the Decay rate of the universe so of theyer is nothing to decay then there is nothing to observe decaying

    4. Daniel Baenziger

      I think Carl would have really enjoyed these videos. Many thanks to Matt and his team for taking part of his mantle. Cheers.

    5. Spiritual Braces

      i always wondered if our universe was just some black hole in another universe...

    6. Chris Howe

      Was there a video that tackled the idea of Tachyons during expansion? My best guess. No. The density of the universe at the Singularity would create a difference in 'c' similar to what we see around a black hole. However, relativity brings us to a screeching halt there since it's from our perspective that 'c' is changing at all. Would this all come together to indicate that a sationary observer during expansion would in-fact have witnessed tachyon-level information transmission? Wouldn't this also mean that 'c' is relative to the observer and thus tachyons would be possible only from a certain perspective? Example: 2 starships travel conventionally at 0.75c towards eachother. The observer on starship a would witness starship b approaching at >c. viola! Tachyons??? This would also mean a new c is in order where 2c is "true" constant???

    7. Elias

      watching this sort of stuff feels a bit like getting my brain spanked

    8. Lelouch Yagami

      We can say 1 day before big bang...

    9. Steve Openshaw

      I am an atheist, but listening to how convoluted all these different creation theories are, it makes me think that it may well just be simpler to buy that some old dude with a beard did it.

    10. Dave Anand

      We only speak of one directional time in the positive direction - What about NEGATIVE Time Axis ???

      1. Back to Seattle

        Entropy wouldn't be to happy about it

    11. robert charlton

      time and space are very complicated, take for example, that we can travel at the speed of light and there are twins, that are astronaughts, 1 of them stays on earth and the other goes on a trip to jupiter at the speed of light, when he comes back, the twin that stayed on earth would be older than the twin that went to jupiter.

    12. Simon Coles

      I'm a bit fan of the Penrose CCC theory

    13. Amzar Nacht

      *heh* Time pre-dated the 'big bang' - but there was no way to measure it as the required atomic vibrations were at a standstill. Nothing got within a thousand light years without being sucked in... Once the trigger initiated, time could then be measured by the vibration of energetic particles that formed soon after. Time as *WE* know it - you know, these bone-encased gray blobs of neurons that have existed for about one billionth of a second on the 'year clock' of the life of the universe (as in, one billionth of a second from midnight, december 31st on that calendar) - is something only *WE* conceived and chose to call 'time', so what time was prior to the creation of our small corner of the greater macroverse well... it had already been defined by others. Perhaps others advanced enough to even manipulate or travel along it *then*

    14. chrisgotagun time

      God is the big bang theory

    15. Faris

      Is anyone else triggered about the way he wears his shirt?

      1. Prestia2011

        Why cause it's lower on one shoulder? Maybe he's got uneven upper body

    16. Viker

      Im watching this video trying to expand my knowledge and get smarter and cause i like space but god why am i so stupid that i dont understand almost a single thing

    17. james caley

      Never trust anything with a singularity.

    18. M Johnson

      It seems like the Universe once expanded to a point of thermal equilibrium is the same as the universe before the big band at thermal equilibrium. What about a Bose-Einstein condensate could it be state of matter at the point before the big bang at the end of that expansion?

    19. 56pjr

      "In the beginning, God created the Heavens and the Earth" (Genesis 1:1).

    20. Tymen Timmer

      One thing that bothers me is the whole t=0 or t=something for that matter. How do you know what time we live in? And what happens from t=-1?

    21. Games Creator

      Thanks for exploding my brain...

    22. Deipatrous

      Your maths is shaky. Which is a pity because this channel is better than most.

      1. djchristian82

        Yea show your mathematical skills.

    23. Traian

      So, with a Planck time as the smallest unit of time and a Planck length as the smallest unit of distance, why is it mathematically such a problem? instead of infinitely divisible 0.something why not make 1 the smallest number possible (1 as in the singularity) and abolish fractions. (one is the smallest number, the next smallest is 2 ...) shouldn't the math solve itself after that? you get as far as you can get as long as you have space time, and before that it doesn't matter because without space time you can't define it. In fact if you want to go back the universe's beginning 2 is the farthest you can go because that's the actual first second and the first measurable size between 2 points (you need 2 at least points to measure a distance or an interval of time. P.S. -for you physicists out there: how is gravity warping space-time ? is the Planck unit of distance changing or what?

    24. Stan TheObserver

      If the Universe was all at one point...then how could it be infinite? Also,dark energy was not all it was at the big bang as it grows as it still perculates out of nothing. Something's missing.

      1. Stan TheObserver

        @djchristian82 They are certain that by any other name a force is expanding the universe. It's everything after that they can't say for certain. Dark Matter on the other hand might just be regular matter,just in microscopic bits and invisible clouds of it. Or not.

      2. djchristian82

        Dark energy is nothing proven just a hypothesis.

    25. Lord Pyrex

      Black holes consume all matter over time and eventually each other and eventually only one exists and eventually even that is taken back to a single point which then erupts back out into a new big bang.

    26. Luigi Cantoviani

      Inflation is not a matter fact event.

      1. Roboprogs

        Yeah inflation theory makes me cringe, too. Any observations of an inflation, or a falsifiable test? My theory is that the universe started are as something about the size of a lumpy beach ball 🤡 (But I don’t know how to test it, so it’s probably crap even more so) As Opus the Penguin said “Well, why not?!?”

    27. Theo0x89

      6:34 _"we trace a path called a geodesic, which in general relativity is the shortest path between two space-time coordinates"_ More like the "straightest" path between two points in space-time. Typically it is the longest path, measured in proper time, which is the measure of length in space time. Also, "between two space-time coordinates" is an awkward formulation. There is no need to refer to coordinates, and the two endpoints of the path would correspond to two sets of four coordinates with respect to some coordinate system.

    28. neil u

      ok, but what size would a black hole be thats the mass of the universe? how could the big bang have started smaller than that? does information theory put a minimum size for the whole universes information to be stored on the surface a universe mass black hole? thanks

    29. Enki Son Of Anu

      Not weird enough

    30. Hecka Nice

      No. Time starts with a point of consciousness

    31. Ive_y 79

      I watche this then I died

    32. Apollo Stone

      No one really knows how the universe started but mainly theories are the only thing to talk about. Again, we know nothing, yet we always explore somwthing.

    33. Jari Haukilahti

      Maybe time started big bang.

    34. memo redspectrum

      planc length has some idea

    35. Akshay Kalghatgi

      Has anyone ever considered the possibility that the Big Bang might have been a White Hole.

      1. Vincent Smith

        He kind of said that that was a possibility in different words

    36. Dominic A

      It’s magic !,no other explanation.

    37. ZERO3690

      I see.. Big Bang is not a theory any more, it is a fact and so we are now focused on other things to solve

    38. quidam

      Hey, great thanks from France !!! I was wondering if you'd talk about the BGV theorem some day as it seems to have a connection with beginnings ? I've heard about it but can't grasp the implications and on what assumptions it rests... Anyways, big big fan of yours !!!

    39. Andrew Pope

      I greatly appreciate this honest attempt at explaining this stuff however I am absolutely none-the-wiser

    40. Underscore Pete

      Is it possible that 3 of our universal forces already existed at the proposed time of the big bang and gravity then occurred for the first time in our universe? Can a universe exist without gravity?

    41. Ajit Jha

      I am inclined towards Holographic Universe. The space itself is a projection, where as the so called reality is somewhere else.

    42. PistolPunch

      What if black holes singularity after vapourizing somehow creates an explosion which causes space to expand and creates new materials. Like dividing by 0. It would create and endlesss cycle of new universes everywhere.

    43. Martin L

      Odd place to put this. I'm an evolutionary biologist, so am prone to be a Smolin fan boy. But this is something different, that all PBS channels have in common. I'm British and am totally sick to the teeth by the very American obsession with religion vs science. You don't really get it in the UK. To be honest, I am just SO cheesed off that everytime I look at something interesting, videos, below the video I'm watching, nearly always carry at least some videos by people who are either crazy, or have no idea what a theory means, and why science must always be agnostic, about everything. Sorry to have a rant. I'm just fed up with this unending war between OCD anti religion, and plain stupid anti science. Drives me nuts. So hooray for PBS, Crash Course etc. I am seriously in love with PBS. If you carry on, you might even get as good as the BBC. HA!

    44. Systematic Error

      ALLAH is the GREATEST. de-news.net/online/video-PyCezBD-5EQ.html

    45. Deborah Mahon

      Our God is an awesome God.

    46. The Werewolf

      Sure. but what about Galactus?

    47. Kyle Buchanan

      you have explained exactly nothing, cmon start making some meaningful videos please guys

    48. penguins forall

      Big bANG rewind 0000

    49. WolfgangLMclain

      Something just occured to me, the weight of the universe at its earliest point must have been ENORMOUS, what did that mean for the spacetime curve of the universe?

      1. LouSaydus

        You should ask your mother, her rear is of similar density/mass.

    50. WolfgangLMclain

      *notices* *reaches into video to tug your shirt into place*

    51. Kirk-Da Rooster Gordon

      Science tells us you can't create something from nothing okay so what created the singularity that started the big bang?

      1. Romel Abou-Akl

        Our laws of science break down at a certain time interval after the big bang, commonly associated with the plank length. I do not have an answer for you, and nobody can answer it because nobody has a good answer to that. Some people have formulated mathematical explanations of how it could have came from "nothing", but there definition of "nothing" can be considered to actual contain something. Also if time does not exist before the Big Bang occurred it actually does not make much sense to ask what happened before it, or what created it since that is a human wording of events that are in a sense timeless. It is hard for us to think of something as timeless. Of course if it stems from another multiverse/bubble universe, etc you can still trace it back to the initial moment in that time frame. Some propose a creator, as there are some logical arguments such as the Leibniz's cosmological argument and many others that attempt to show why there must be one. This is a field of fascinating advancements, logic, physics, mathematics and in some senses even spirituality as we seek where the atoms that make up our consciousness and everything around us stem from. Good luck on your journey for knowledge.

    52. Ulfat Dawood

      Doesn't the Big Bang Theory violate the "Law of Conservation of Mass" ??

      1. Theo0x89

        Conservation of mass hasn't been at thing since Einstein discovered that mass is a form of energy. What you mean is conservation of energy, for which you would need a general definition of energy, which doesn't seem to exist in general relativity. But that's beside the point of your question, I guess, because you seem to think that the energy content of the universe somehow changed at the Big Bang. The Big Bang Theory doesn't say anything like that. It only says that the energy density used to be very high at some point in the past from which the universe went on to expand.

    53. Brian Cananzey

      what if the universe does have a cyclical big bounce and each time it bounces it grows bigger than the last bounce. eventually if exceeds its ability to crunch any longer and after its last bounce it expands forever. We are in that expansion? Hmmm? Like a ball bouncing every time going higher and higher till it leaves the surface of the earth? ....excuse my while I hit this joint again!

    54. Harry H

      Alien in another universe made our universe, their universe was in turn made the same way, ad inf, different universe different laws

    55. A Tothetop

      Every Christian who appeals to the Big Bang theory from a causality perspective needs to see this!

    56. Subodh Khandekar

      At 5:22 ... It's not 3 dimensional... It's 4 dimensional space !!!

    57. Lucid D

      The big bang is like the mitochondrial eve in genetic, just a logical response from a bad question or attitude. Same with the chicken or the egg? question. They are just bias rooted in our social understanding and psychology. There is no mitochondrial eve that ever existed and both the egg and the chicken are phases in evolution, both cell forms and bodies evolved together to produce one or the other.

    58. tenaciousvalor


    59. Timothy Bucci

      Patterns in the universe repeat themselves. The universe probably will too. If all of matter had a specific origin, and the amount of mass in the universe has a limit, even if myriad... eventually acceleration will shift back to deceleration and combine back into a single singularity black hole once again. Maybe after .54 googol years, is my guess

      1. Timothy Bucci

        @Adrian Constantin But they have only been observing this ancient universe for what, 100 years? With pristine telescopes and such? They may be misperceiving things.

      2. Timothy Bucci

        @Adrian Constantin Or acceleration is bullshit. The Millennium Simulation shows what has been theoretically observed, and there are flows or currents of galaxies headed toward specific gravitational wells.

      3. Adrian Constantin

        One way this doesnt work is if acceleration / inflation never stops ... than gravity does not win

    60. Dima Chotin

      Did he just say Steinhardt-Turok model? Like in... a hard as stone dinosaur hunting american native?

    61. Sarath Ambalapatt

      Imo Past and future exists because we have memories and thoughts There is only just PRESENT and its always CHANGING!

      1. David Heizer

        This is why I think it's silly wondering why we can't see all of the 11 dimensions predicted by string theory: we already know we live in at least a 4-dimensional universe, but only three of those dimensions are physical. We really cannot directly perceive the time dimension; we experience it only through the contrast between what exists at the moment and what our memories tell us used to exist.

      2. P Sigh Ko

        It seems most scientists reject this presentist view (and favor the eternalist block universe). You're a minority, my friend.

    62. jojolafrite90

      I"ts tricky to talk about, to talk about the size of an infinite universe. That was a shitty rime.

    63. froop

      the real question is: is time a conserved property?

    64. MoscowBaseStation

      Please help me. I feel in order for the big bang to happen there must be a space within the big bang to take place ..

    65. Aarond Anton

      The science of the Big Bang as told by science is flawed in that the heat and forces involved would kill off any living organism effectively sterilizing everything in the Universe. Good news is that God created everything from a single point of origin and in that moment time started God the Father and Creator in Heaven is infinite and eternal.

      1. Aarond Anton

        @P Sigh Ko yup trolling for fishers of men

      2. P Sigh Ko

        Lol. xD Troll.

    66. JT

      Finally someone who actually knows what they're talking about

      1. Kyle Buchanan

        hes not got a clue r u mad

    67. SaStrixS

      An even better question would be "What time did the big bang start?"

    68. Rosolino Lo Sciuto

      Il N.W.O. ha un programma specifico e' determinato con l'Unione delle Nazioni Repubblicane impartito dalla coscienza universale

    69. Osvaldo Lopez

      For those using cc, at 10:50 it says "brains" but it should say "branes"

    70. Forbes Media

      this guy needs a stylist or someone to tell him to wear his shirt properly -_- it is distracting