How Big is the Universe?

How Big is the Universe?

The Universe. How big is it? Does it have
a center? Does it have an edge? Is it getting bigger, and if so, why? Well, we know that there are two different
meanings for “universe” – first, the “observable universe” is everything that we’ve been able
to see, or observe, thus far. And second, “The Universe” (or “the whole universe”) means
everything that exists or has existed, or will exist. More specifically, the observable universe
is the region of space visible to us from earth. And since The Universe is only about
13.8 billion years old and light takes time to travel through space, then regardless of
what direction we look, we see light that’s been traveling (at most) 13.8 billion years.
So it’s logical to think that the observable universe must then be 2*13.77=27.5 billion
light years across – but it’s not. That’s because over time, space has been expanding,
so the distant objects that gave off that light 13.8 billion years ago have since moved
even farther away from us. Today, those distant objects are a bit more than 46 billion light
years away. Multiply times two and you get 93 billion light years: the diameter of the
observable universe. To give you a sense of scale, the size of
the earth within the observable universe is roughly equivalent to the size of a virus
within the solar system – although that doesn’t help much because we can’t really appreciate
the incomprehensible smallness of a virus nor the bewildering bigness of the solar system,
either. So let’s just say that the observable universe
is stupendously big. But The Whole Universe, as far as we can tell, is a lot bigger – space
is most likely infinite! Or at least it doesn’t have an edge, though the difference between
those is another story unto itself. Now, what about the center of the universe?
Well the observable universe has a center – Us! We’re at the center of the observable
universe because the observable universe is just the region of space visible from earth,
and kind of like how the view from a very tall tower is a circle centered on the tower,
the piece of space we can see from here is naturally centered here. In fact, if you want
to be more precise, EACH ONE OF US is the center of our OWN observable universe. But that doesn’t mean we’re at the center
of The Whole Universe, just like the tower isn’t the center of the world – it’s the center
of the piece of the world that it can see – up to the horizon. But just because you
can’t see beyond the horizon doesn’t mean there’s nothing there. And so it is with the observable universe.
Looking up at the sky, we see light light that’s at most 13.8 billion years old and
coming from stuff that’s now 46 billion light years away. Anything farther is “beyond the
horizon”. But each second, we see new, even older light coming from slightly farther away
(one light-second farther, to be precise), and so our view of the cosmos is literally
getting bigger all the time – all we have to do is wait and watch as the universe ages
and light from more distant places has the time to get to us. So here we are, sitting at the center of our
observable piece of the Whole Universe. How big is the universe? Well, the observable
universe is currently 93 billion light years across. The Whole Universe is probably infinite.
Does the universe have an edge? The observable does (it’s 46 billion light years away in
any direction), and The Whole Universe has a temporal edge (or what we call a beginning)
but almost certainly not a spatial one. Does the universe have a center? Again, the
observable universe does: YOU! The Universe as a whole? Almost certainly not.
And is the universe getting bigger? Yes – space is expanding, which makes both the observable
universe and the whole universe bigger – plus, over time, we see older and older light coming
from farther and farther away, so our observable universe gets bigger that way, too. And that, in a nutshell, is our view from
the tower. You are the center of the universe. And so am I. And so is everyone else. And
so is no one. 0 this episode a minute physics is
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universe has the size and shape that we think it does check out how the universe got its spots
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100 thoughts on “How Big is the Universe?

  1. What about the cosmic background radiation? The hydrogen plasma in our early universe which these observable microvawes origin from is opaque, right? Doesn't this wall of plasma shorten the diameter of our observable universe, since we can't observe what's behind it?

  2. Okay.. this may be a stupid question, but if the universe is constantly expanding, how do we know that the "new" light we see is actually coming from farther away and not just the same light observed from a farther distance simply because of the expansion of space? I love your videos, minutephysics, this question just popped in my head

  3. 2:35 This part is actually wrong , because since the universe is expanding at high speeds , light from places beyond the observable universe will never get to us ( theres a vsauce video talking about that )

  4. The observable universe is not changing… The universe is expanding faster than speed of light so we are "loosing" data from our observable universe while time go on… In the future, there will be a day where you will not be able to see anything outside our galaxy, every other galaxy will be far away from us and after the edge of the observable universe.

  5. There are things missing from this video. Space is expanding and the speed of expansion increases with distance meaning space a few miles from you is expanding faster than space close to you. Therefore, space a few billion light years is expanding faster than light speed, so the light of something in that space will never reach us. If currently the observable universe is 13.8 billion years then that is the threshold where space expands faster than light. The size of the whole Universe therefore is something we can't measure.

    If the big bang is true then there must be a center of the universe but we so far don't know where that is. I wonder how the center of the universe would be.

  6. Outer Space is bigger than the Whole Universe because Outer Space is Everywhere Outer Space is Infinite Than the Whole Universe

  7. How is more of the universe visible to us if the universe is expanding? According to Hubble's law, the rate of expansion of the universe is expanding, which means that past some certain point, the universe is expanding faster than the speed of light, hence any light they emit right now will never reach us (since light travels at c, but space is expanding in the opposite direction at a speed bigger than c). If this is true, then how are we able to observe "more" of the universe?

  8. I am puzzled about a remark in this video. How can light from more and more (older) objects reach us over time if we already see the afterglow of the Big Bang in form of background radiation? There should not be anything older than this.

  9. Doesn't the observable universe have a hard limit because as the universe as a whole expands light from distant objects is redshifted out of what we can measure?

  10. If the whole universe is infinite, then it can't be getting bigger. If you say it's getting bigger, you are saying it cannot possibly be infinite.

  11. As far as I know the observable universe is getting smaller… The reason is the expansion. The far galaxies we can abserve will be hidden in the far future. A person looking into the cosmos in an far (billions of years far) future would not see any other galaxy than our own. All the other have accelerated from us so fast than light would never reach us.
    Or at least that is how I understand it

  12. The universe not having an edge is NOT the same as saying it is infinite! What a crude distortion and assumption! By the way, space cannot be infinite, just as matter cannot be infinite. Only concepts, such as numbers, or operations such as division, can be infinite. If you don't think in terms of mind-body dualism, you simply cannot understand infinity. Infinity is NOT the same as a very large number. It is a concept.

  13. but if the whole universe is infinite then it means thst any point we pic has infinite space around it meaning all of it is at equal distance and that is infinity so any point we might pick is the center of the universe

  14. if the universe is infinitely big, then how does time dilation work? because if the universe is infinite, then wouldn't it technically be impossible to move relative to the universe? and if we are using another object in the universe to compare our speed to, such as the earth, depending on how you want to look at it then you could say it was actually the earth moving instead of you. so then what determines who experiences time dilation? the universe is full of things, but can the universe itself, being infinite, be used as a frame of reference?


    • Energy may be converted, but energy cannot be created or destroyed.
    • There must be an input of energy for there to be an output of energy.
    • The output of energy cannot exceed that of the input of energy.
    • An input of energy may be converted into an output of energy, and an output of energy may be converted into an input of energy.

    As Such

    Although, energy may be converted into other forms of higher or lesser levels (types) of energy or matter, energy of its own all-pervading universal existence, cannot be created or destroyed.

    Energy of its own all-pervading universal existence is infinitely – eternally – universally indestructible.

    Energy of its own universal pervading universal existence is infinitely – eternally – universally boundless.


    As these laws of physics are universally accepted by all members of the world science, as to being absolutely incontestable, so it follows that any theory that has been proposed and accepted by the world of science, or has been proposed in the name science.

    That ignores or contravenes these fundamental laws of physics (E.g. The Big Bang Theory) regardless of all of the vested interest politics and peer group pressures of the scientific world, in unequivocally not worthy of the paper it has been written on, or of publication.


    The all-pervading "energy of the universe" may be converted, but the all-pervading "energy of the universe" cannot be created or destroyed.

    For there to be an output of energy or more namely an output of energy in motion, which otherwise is termed as being a motion of work or force, there must be a force of energy input.

    The force of the energy in motion output cannot exceed the force of energy in motion input.

    For every energy in motion force of action, there is an equal and opposite energy in motion force of reaction.

    For every exertion of force sub-divided as in e.g. the form of a shotgun effect, the sum of the force used and delivered by all subdivisions of the exerted force is equal to the sum of the whole of the quantity of in motion energy exerting the force.

    The total sum of the force of exerted against an immovable surface area is equal to the total quantity of the in motion energy exerted.

    The sum of force exerted to form a particle or a density of matter is equal to the sum quantity of that particle or density of matter.


    As, these laws of physics are universally accepted by all members of the world science, as to being absolutely incontestable, so it follows that any theory that has been proposed and accepted by the world of science, or has been proposed in the name science.

    That ignores or contravenes these fundamental laws of physics (E.g. The Big Bang Theory) regardless of all of the vested interest politics and peer group pressures of the scientific world, in unequivocally not worthy of the paper it has been written on, or of publication.

  16. Universe is expanding.
    Does that mean every object is moving away from each other?
    Every object's size is increasing? (maybe due to increase in intermolecular spacing or something like that)

  17. Since we know that if an object at rext explodes, the total momentum of all the particles it broke into averages out to zero.

    Can't it be like, from the point where big bang took place and lead to formation of universe that contains all types of matter, antimatter or dark matter etc. Or even those things we don't know yet, be a point where everything in universe if added averages out to zero??

    Maybe that could explain existence of universe as well as notingness at the same time?

  18. If the universe is eternal, it will do everything an infinite number of times, including dying out. But it can’t, it’s eternal. I found a loophole guys!

  19. So was all mass in the Universe once inside the big bang? If so how did mass even end up outside the scope of the observable universe? Light from these places traveled to us faster than they could have moved away from us. Why would light still need time to reach us?

  20. Ok so the universe is 13.7 bln years old but the size of the observable universe is 43 bln light years in every direction so its expanding at more than 3c. Can someone explain this?

  21. wait is this video correct in saying that we'll be able to see more as the observable universe expands? i thought i read somewhere because the universe is expanding faster than the speed of light and that means that our cosmic horizon will shrink continuously, which, i assumed, meant that we'll be able to see less, not more. Or am i missing something here?

  22. You said that our observable universe keeps expanding, which is partially true, but the universe keeps expanding too, faster than our view is expanding. So our view will be larger, but it will always have less matter in it than now.

  23. I disagree and here’s why. Assuming the Big Bang created the entirety of our universe, light has only been able to reach 13.8 billion light years away from the starting point. Knowing that nothing can travel faster than light how can there be matter beyond light itself.

  24. I see a major issue with what you said in this episode. As light travels through interstelar space, it gets redshifted, due to the expansion of the space itself, but from what I've learned from channel PBS Spacetime, the expansion happens to be faster than the speed of light, as to the space expansion, light speed limit does not apply. If this is true, basically the part of the universe we see shouldn't allow us to see more distant objects than those we currently see, and also it should get more empty over time, as the space between our galaxy and other distant galaxies expands in a manner that makes at least part of those galaxies "run away" from us.

  25. If the universe is growing, how is it infinite? And whaere does the growing take place if there's no edge to grow from?

  26. The observable universe need not be a sphere with the earth at the center, since spacetime is curved. Also, the curved spacetime is also responsible why the observable universe is larger.

  27. So if the Universe is expanding,and space is infinite, does that mean that there is space beyond our universe? It has to expand somewhere. Or is it somehow creating space with its expansion? So weurd

  28. and if the earth were flat?, when the Antarctic ice is thawed, it will be possible to go to lands that are far beyond, there are no real photos of the earth from space, they are all images of hollywood

  29. but since the universe is expanding faster than the speed of light, won't there be some things out there that we'll never observe?

  30. But… But…
    I hate it when this happens.
    Still subscribed. Still like your video. I despise that I am unable to listen to the music that is in this video without searching through perhaps tens, thousands, hundreds of tracks by Nathaniel.

  31. how does it make sense that the universe doesn't have a center, when the theory about the big bang states that the universe startet out compressed into a very very small point and then expanded outwards – from the center of that point?

  32. If the universe is truly infinite then anything that has a nonzero probability of happening has to occur very far away in the universe so yeah firefly s2 exist on an alternate version of earth very very very very very very very very very far away

  33. 2:39 The acceleration of universe expansion makes the cosmic horizon expand faster than the light cone, so actually there's less and less we can see.

  34. I dont get it. How can the universe get bigger, if it is infinitely big??? The fact that it grows must imply that it has an edge…

  35. The fact you said infinite and that we are the center seems to contradict like every other space info i've come across about the expansion of space. for the observable universe its moving away from a point and based of how stuff is moving they can tell it came from a point. and we aren't that point.

  36. doesnt space expand in front of the light that is coming towards us from distant stars? if yes doesnt that mean that the whole calculation is more complex?

  37. But isn't the universe expanding faster than the speed light travels and therefore there are objects that emitted light we will never see unless we move towards it at equal 'speed'?

  38. I thought our observable universe was getting smaller because it's "expanding" faster at the edges than the light can travel to us. Basically, all the space in front of that light is expanding faster than the light can travel through it.

  39. Eeeh isn't our observable universe actually getting smaller because of the accelerating expansion (dark energy)?

  40. Shouldn't the size of the observable universe be calculated by the distance light has covered since the origin of the earth? I mean why does he say that with the age of the universe?

  41. Is ALL superclusters rushing away from each other? If no then the universe is not expanding. We should not conclude on the universe expansion if we only see some superclusters is moving away, correct?

  42. If universe is expanding at the speed of light, then the observer is moving away from the light source at speed of light, thus how will the emiited light catch up or reach the observer?

  43. IF the universe is infinite, doesn’t that mean infinite possibilities and outcomes. If that’s true, literally everything you can thing of is possible somewhere else.

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