How Big Is the Universe?
How Big Is the Universe?

I’m sure you have found yourself looking
up at the night sky and wondering just how big the universe is. How could you not?! It’s just so vast, and we are just so tiny!
It’s almost impossible not to ponder just how vast it really is, how far it reaches. And I wish I could tell you exactly how big
the universe is. But we don’t really know. I mean, not only do we not know, but the most
logical guess you might make — based on all of the latest, highest-tech observations that
we’ve made — turns out to be … not even close. And the unknowability of the size of the universe
comes from the fact that light takes time to get to us. The Sun, for example, is so far away from
Earth that it takes light about 8 minutes to get here. So, when you look at the Sun — which you
should never actually do, by the way — you’re seeing it the way it looked 8 minutes ago,
when the light that’s now hitting your eyes left its surface. Then there’s Proxima Centauri, our nearest
neighbor star. Light from there takes 4.2 years to get here, which is why we say it’s
4.2 light-years away. So we’re always seeing how it looked 4.2 years ago, not what it looks
like now. So basically, the farther away you look into
space, the farther back in time you’re seeing. Which is really cool when you think about
it. Now, the first light in the universe that
we’d be able to see, started traveling about 13.8 billion years ago — that’s around
300,000 years after the Big Bang. Before that, the universe was so dense that
it was basically opaque. There was light — but it couldn’t get very far. So, we can only see as far as where that first
visible light started traveling from — this is the edge of what’s called the observable
universe. But here’s the thing: The universe is almost
certainly bigger than the observable universe. Cosmologists think that there’s a lot more
out there, beyond that edge, and if you could somehow see the rest of the universe, it would
look pretty much the same as the observable one, with the same kinds of stars and planets
and galaxies. It’s just so far away that its light hasn’t
had a chance to reach us yet, even though it’s been traveling for billions of years. So, we know that there is more of the universe.
But, again, nobody knows how much more. To get a little closer to understanding what’s
all out there, let’s start with what we do know: How big is the observable universe,
at least? From everything we were just talking about,
you’d think that the observable universe would be basically a sphere that extends 13.8
billion light-years from Earth … … because the universe is about 13.8 billion
years old, so that’s how long that first light would have taken to reach us. By this reasoning, from end to end, the sphere
would be twice that size — 27.6 billion light-years wide. But it’s not. Because, light might have left the edge of
the observable universe 13.8 billion years ago, but by now, the spot where it came from
is actually much farther away. OK … so how did that happen? It’s because of another endearingly fascinating
trait of our universe: … it’s expanding. And fast. Everything in space is flying away from everything
else, because space itself is expanding. It’s kind of like dots on a balloon — the
farther away the dots are from each other, the more the space between them expands as
the balloon inflates. So, we might be seeing light that’s been
traveling for 13 billion years, but during that time, its source has moved much farther
away from us. Astronomers can figure out how far, because
light that’s traveling toward us through expanding space will be shifted toward the
redder end of the spectrum. And that is how we know that — even though
light left the edge of the observable universe 13.8 billion years ago — that spot is now
46 billion light-years from us. Which means that the observable universe is
twice as big across — 92 billion light-years wide. So, all of this has left us able to see only
a tiny part of the universe, with no real sense of how far it goes. Which is why you’ll hear all kinds of mind-blowing
ideas about what the universe might be like — maybe it’s infinite, maybe it isn’t,
maybe there are actually LOTS of universes and we’re just living one version of the
infinite variations of history. We simply don’t know what’s out there,
and we probably never will, because most of the light out there, beyond the edge of observability,
will never reach us. The universe is just expanding too quickly
— past a certain point, everything is moving away from us faster than the speed of light. And for us, light equals information. Without it, we are just … left in the dark. Thank you for watching this episode of SciShow
Space, and thanks especially to our patrons on Patreon who help make this show possible.
If you want to help us keep making episodes like this, you can go to
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100 thoughts on “How Big Is the Universe?”

  1. Viral Videos says:

    Rig Vedas already mentioned all this and structure of universe thousands of year ago .. but we have ego and attitude problem of thinking Ancient Indians as fool

  2. Dhrit says:

    so will earth move away from the sun, like the dots on the balloon; since, everything is moving away from everything else?

  3. gustavo soto says:


  4. Blubb340 says:

    so it's bs when someone say that light is the fastest thing in the universe. if the "outer" universe moves faster than light than it's possible to move faster than light because these things do that. I feel like our science is crap -.-

  5. onlineamiga says:

    I've always been curious about this one. They say that the universe is expanding faster than the speed of light, but newtons law says that nothing can go faster than light. So how does it work?

  6. ToneyCrimson says:

    If universe have a edge..then whats behind it?

  7. David Levesque says:

    The universe is as big as the outer edge of the clothes you're wearing, and time is the furthest distance you can see and here at any given moment. In your skull is memory and forebrain stuff that gives one this universe of immeasurable big/nothingness. And in opinion, that's where one lives. Even with ones penis in an OS or body enveloping a baby. Because there's no one else with your name exact birth date and personal view in your head. And that's how big the universe is. Of course slavery changes stuff. But like the woman character on Seinfeld said,'Big!'

  8. waltersumofan says:

    no edge

  9. True Casual says:

    1 squaremeter.

  10. Wojtek Szymanski says:

    You said that " past a certain point, everything is moving away from us faster then the speed of light" Can you expand on that? I was under the impression that nothing is faster than light

  11. Darth Mongoose says:

    Hard to get my head round this. So if the universe began 13.8b years ago, does that mean it has been expanding by at least 3x the speed of light (as the radius of observable universe is estimated at 92/2 b lightyears)? How is that even possible?

    And if it is still accelerating, does that mean that at some point pretty much all of the stars will be accelerating from one another at the speed of light, at which point we (or whoever is still alive at the time) will only see a completely dark, starless sky?…

  12. J Cole says:

    isn't the universe suppose to be flat?

  13. Ryan MacFarlane says:

    As Bill Nye might say, It's BIGLY HUGELY HUGE!

  14. Bauk says:

    the universe is expanding faster than the speed of light??really!!?

  15. Java says:

    If earth is in universe then universe is in what?

  16. Caleb Ueckert says:

    quick question, what's in-between galaxies?

  17. pranamd1 says:

    NO EDGE!!!!!!!!!!11111

  18. etiennegandon says:

    I have several questions here :
    What about gravitational waves ? Could they add information to what is out the observable universe ?
    I know this might sound stupid but I kinda dont get what you say Hank around 2:10 :
    I'll try to explain :
    1/ The universe is 13.8 My old. Right ?
    2/ We receive light that has been emitted nearly 13.8 My ago (Limit of the observable universe). Right ?
    3/ At t=0 all the matter was about "in the same place". Right ?
    -> To me it seems likes we're receiving light from the point we were 13.8My ago. Which mean we traveled faster than light ?

    Also how's the light speed affected by universe expansion ? Is it still 3.10^6 km/s no matter what or is it v_light ± v_space_expansion (depending on whether the light goes with the expansion or against it, which would mean there's is a center from which the universe expand …) ?

  19. TheKimpula says:

    I look up in to the sky and wonder, why isn't everyone on earth an an existential nihilist..?

  20. Mili & Loui Budgie says:

    what if there is a line(edge), and behind that line must be something else that causing the line(edge) is there. what is that thing that caused the line and what is that thing behind the line(edge) what is the point of it, and all those zillion galaxys athmospherers etc… only built or exist to keep us alive on this small earth? doesnt that kreeps us out. i think behind that edge are million billion zillion edges bigger than we know, and there are angels-prohpets and GOD. compare it like prisons on earth with rules ps. dr sam

  21. Ha Lert says:

    Time and distance in the universe give no longer clear answer to human till today. It is probably both end of the space edges to be the same point. We are really so tiny thing comparing to the universe.

  22. scabiniful says:


  23. Arcane Archive says:

    3:54 pure poetry

  24. BigSky Theroy says:

    Did you notice how the dots on the balloon got bigger? Will matter also expand, along with space, at the edge of the observable universe? And what about time? Is it "expanding", slowing down, out there? As for matter matter beyond the observable universe travelling faster than light, I thought light speed was was the absolute speed limit, so the light in the opposite direction would be stationary? My brain is to feeble for this stuff.

  25. Sameer says:

    So Vast yet perfect creation of the Creator All Mighty.. Imagine about how a Scripture more than 1,400 year old could indicate except that it is the word of the All-mighty Himself.
    CHAPTER – 67 ( VERSE : 1,2,3) & Glorious Quran says :
    Blessed is He in Whose Hand is the dominion, and He is Able to do all things. (1) Who has created death and life, that He may test you which of you is best in deed.[] And He is the All-Mighty, the Oft-Forgiving; (2) Who has created the seven heavens one above another, you can see no fault in the creation of the Most Gracious. Then look again: "Can you see any rifts?" (3) Then look again and yet again, your sight will return to you in a state of humiliation and worn out

  26. Kevin Hosford says:

    Is it bigger than a bread box?

  27. DivineRift says:

    How is the universe expanding away from us "faster" than the speed of light when matter cant travel faster than light?

  28. KWT says:

    No one can imagine how big is our universe. My mind stops when I think about our galaxy radius. A car that is 300.000km/s fast needs 100.000 years to cross galaxy and there are billions of other galaxies in the universe. My mind just cannot go over this.

  29. Muhammad Ibrahim Alvi says:

    How the hell can things beyond the observable universe travel faster than light?

  30. Nicholas Nefsey says:

    I hope someday we will be able to go out further than the moon

  31. Jovanny Collado says:

    So if an object appeared one lightyear from earth, and stayed there for exactly three months. Then started heading towards earth at faster than the speed of light and made it half way to earth or half a light year, in a few minutes and stopped again and then shifted to the right what would we see?

  32. UnderScare Creator says:

    wait a second…
    if light from outside the observible universe is still traveling to us…
    does that mean in the future… we'll be able to see more of the universe?

  33. Paul Smith says:


  34. Will Gale says:

    So wait, you said that it's moving away from us faster then the speed of light at the end of the video, is this misspoken, or misunderstood on my part? I'm a tad confused, how is this possible, if the speed of light is indeed a constant limit?

  35. Creation Founder says:

    I do not wonder about questions I already know answers to. The universe here is as vast as life is.

  36. The Brony Notion says:

    We are in the universe.
    Planets live inside the moon.
    A rocket ship can go to space.
    A rocket ship can go to the moon.

  37. dhompe3 says:

    You said that at a certain distance from us, everything is traveling away from us faster than the speed of light, but isn't that impossible? I mean for anything to travel faster than the speed of light. Or is it actually that we are moving away from "EACHOTHER" at a speed faster than the speed of light. ??

  38. Ethan Looney says:

    My favorite Theory is that each and every Black Hole is a Universe. And that our Big Bang was the start of a black hole.

  39. HalcyonSerenade says:

    In all likelihood, the universe is probably banana-shaped. Like Earth.

  40. ctekbas says:

    still not bigger than Kanye's Ego

  41. CS Official says:

    Yeah there's infinite number of realities were smaller than the thing we live in there's more planets , Suns, galaxies, black holes, and universe's grains of sand in the world.

  42. Daniel Hawk says:

    so wait, at the end the video says the universe is moving away faster than the light to get to us. This means that part of the universe is moving faster than the speed of light. which i thought was a law or speed that could not be pasted?

  43. Johnny Luken says:

    I've only heard of the idea of an infinite universe or a finite one.

    What if the universe is an infinite outstretching interval of infinitely large spherical shells? Infinitely infinite? Metainfinity is a valid mathematical concept.

  44. Ricardo Lemus says:

    the concept of infinity ia a glitch in the matrix

  45. Zain Abadin says:

    Best host

  46. Mike says:

    The only way you turly understand is if your tripping then it hits you like a ton of bricks !!

  47. Necrotoyip says:

    boy I bet you could fit a lot of cereal in here

  48. Indra Lesmana says:

    Sometimes i do really want a super sexy beautiful blonde girl hosting this show and watch their expression they are making when they try to understand he narration they have to read in order to explain to us how do science of space at work.
    so. who's with me?

  49. Jon Lloyd says:

    what would happen if our point of reference was closer to the source of the light?
    Example: Say (Hypothetically) we build a telescope that was able to leave our galaxy and travel as close to the speed of light in any direction, for say (Lets say its visiting the Alpha Centuri system, would they still be limited to the same light that we are receiving here, or would they be able to see further back then us due to their frame of reference?

  50. Orange Juice says:

    I got a question
    When you look at the sky, you ask yourself what's behind it? Well there's space and planets behind our sky. But what is behind our universe? What is universe? Cloud shaped thingy that levitates about water somewhere? What is it? I'm so curious fuck I think I'll go nuts

  51. commonsensedatcom says:

    The universe is infinite because it keeps expanding

  52. Austin Thompson says:

    I don't know how big the universe is just know Yahweh created every thing now repent and get right witb Yeshua before its to late

  53. Adam Biewer says:


  54. Flat Earth says:

    Creation is finite, consciousness isn't. Deception sandwich with extra mustard please.

  55. Shez says:

    46 billion light years the universe size

  56. Someone Else says:

    the possibility that the universe is expanding faster than the speed of light is unsettling. in my opinion.

  57. LoDiZZle Dabadollipofdaisy says:

    I experienced a sensation of horror towards the end of this vid

  58. Amanda Jo Henriquez says:

    Hmmmm, did the calculations presented in this video also account for the increase of speed of expansion as time increases. Isn't the universe accelerating as it expands?

  59. SarahJoJo 97 says:

    So… Hella. Hella big.

  60. Tausif ali says:

    Kinda scared after watching this

  61. DeeZanic says:

    I think we have to get rid of "space" if we want to explore the universe beyond the speed of light

  62. They Live says:

    If talking with hands is a requirement for a presenter on this channel then please use more than three gestures over and over 😛 Interesting videos though.

  63. Zizo clever says:

    This host is my fav ^.^ Very nice episode guys well done!

  64. Mr GuyMM says:

    Would it be possible, with sufficiently sensitive instruments and enough observation time, to track the movements of the most distant visible objects and use that data to extrapolate the gravitational presence of objects just beyond the visible horizon?

  65. djgruby says:

    A mindblowing episode! Thanks!

  66. Grey Wolf Alpha says:

    awesome info , as always .

  67. Derrick Landers says:

    Even at 96 Billion Light Years across I could probably still find a lawyer for my "trip and fall" accident which occurred in the 10 Peruvian Binary Star Cluster!!😝

  68. MDPixiegirl 2345 says:

    "Have you ever look at the sky and pondered how big the universe is?"

    Me: Well I haven't

    "It's almost impossible not to!"

    Me: Does this make me special? Because I haven't."

  69. Julio Pinon says:

    the universe is big
    really big
    believe me

  70. Matas says:

    Never thought to say that, but the speed of light is slooow AF
    also another video, which answer is: we don't know 🙁

  71. William Rosen says:

    NO EDGE!

  72. William Saunders says:

    I 💘 hank he provides me with my scientific fix of my daily life and he is awesome

  73. William Saunders says:


  74. chronoss chiron says:

    wait did he just say things are moving form us faster then light

    i had this tought many years ago if two objects can go 80% light speed in opposite directions then technically light can never reach them….now imagine if you cant see it but it has mass what that means…its invisible but might show effects or affects of gravity on things passing buy we can see….anyone studied this to say how much mass in universe this could be?

  75. rlylolno says:

    Why do all these guys talk like this

  76. Christian Turner says:

    So where did the Big Bang happen?

  77. Al Cameron says:

    I think space is infinite.

  78. light564 says:

    Wait you said the universe is 13.8 billion Old however you said 13.8 billion years old was about 3000 years after the big bang. So by that logic the universe is exactly 16.8 billion years old. What if the universe is much older? If the reason why we say the Universe is 13.8 billion years old Is because we can only see that far or the light from the stars travel that far? What it for 3000 years off? Then how to read determine that the star we see is about 4 light years away. How do we Measure how long it takes for it to get to us? Finally is the theory of relativity everything or is it just 1/2 of the equation or is it really the answer to everything we find ?Or are we just guessing ?

  79. Xalaikhan Master says:

    There are so many things in our universe that reality causes lag issues. That's why we see our sun 8 minutes ago.

  80. Bigyeti Technologies says:

    What's the limit we can see? How far away is space expanding > c?

  81. Titanic says:

    Hold on. Say light from a galaxy 13 billion light years away from where earth will be has started to travel. The space expanding pulls the light back. That means it takes long to reach us. Space is expanding at a rate, so the light will reach us in 17 billion years. This does not go along the lines of what you said before. !?!?

  82. Freeman says:

    I don´t agree that there is light that will never reach us. There are indeed objects in the universe whose distance from us is increasing faster than 2c, but this is due to space expanding and for any light travelling towards us, this space is expanding both in front but also behind it. So even though the distance it has to travel will be increasing for a long time, the ratio of its distance to its origin to its distance to us will keep increasing, meaning it will have to reach us eventually.
    PS: If you´ve meant to say that universe will probably end before this light can reach us, than you are probably right, it´s just that there is a finite amount of time a light from any point in our universe needs to get here.

  83. Pixx says:

    It's kind of hard to imagine how much a light year is, but a light year is 9,461,000,000,000 km. 742,505,101.24 Earths all lined up would be one light year long. It would take you about 7,200,152 years to travel one light year if you were going 150 kmph. Wow.

  84. Aaron Lowe says:

    Can't mass from the unobserved universe explain the mass we think comes from dark matter? On second thoughts, no it can't, because the way a galaxy rotates explains the amount of mass in it. Adding a load of mass dispersed evenly around it would not explain why it rotates the way it does. back to the drawing board. Hangman anyone?

  85. Vegarot Fusion says:

    It's infinite. If you think it's not then give me an example. It's the only logical conclusion.

  86. Malin Zoe says:

    That just blew my mind 🤔

  87. Kai Na says:

    The universe is not black, it's transparent

  88. Kyle Alexander says:

    So simply being able to look or hear faster than the speed of causality will expand the universe that we know?

  89. Vicente Cardenas says:

    If nothing can travel faster than light, how can the universe be expanding faster than light??? Did I misunderstand or did I hear something he didn’t actually say??

  90. Mariano Calvin says:

    will we ever find light that shows the Universe is older than what it is

  91. Gordon Marshall says:

    Now wait just a gosh darn minute. You can't just say the rest of the universe is moving away "faster than the speed of light" and end the video.

  92. Ruth Gonzalez says:

    Does anyone know how I can show this in 3-D? Should I inflate a baloon? I have a project due and idk how to show this concept in 3-D to my class and teacher

  93. steadytube says:

    how can the universe be expanding faster than the speed of light when the speed of light is the universal speed limit. as carl sagan said, thou shall not travel faster than the speed of light.
    its the universal constant.

  94. MrXanthios says:

    When you feel small and insignificant in front of universe's vastness, well… Probably you are.

  95. Wolf Cousins Eddie & Nila says:

    We basically figured out how to go back in time

  96. pool stunner says:

    Anything (matter) occupies space ! What does space occupies?
    Where is it expanding ?

  97. integerrandom says:

    Definitely bigger than 2 football field combined

  98. Maxim Dabster says:

    Does space expand by stretching like a rubber or by growing more space? Can you devide space into smaller ‘particles’?

  99. Marco Rivieccio says:

    I am there anyone out there who could explain to me what is this force moving faster than light?

  100. SomeDudeOnline says:

    I have a question that i probably used to know the answer to and that this video may address. I'm at work atm so I can't rewatch this video to see if it answers my question so I'm leaving my question here in case I forget to watch the video later.

    If the Observable Universe has a diameter of 96 Billion Miles then why do Astronomers report observing stars that are 13 Billion light years away and say they're looking back to just 800 million years or so after the Big Bang? Shouldn't they need to look at stars closer to 42 Billions light years away to see this far back in time?

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