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Is Our Universe Really, Really Big or Truly Infinite?


Space is a massive place, in fact it is potentially infinite. But is it really truly infinite, or just extremely big? A new video takes a closer look at our universe, and asks the question whether it is infinite or not.

The video also gives a lot to think about. It talks about how even if you could continue to go across space forever without finding an end, it would necessarily be infinite, it would just have no edge. Think of it kind of like Earth — there is no edge to the Earth, but it’s clearly not infinite. Then again, it also notes that it’s really hard to say one way or another if our universe is really infinite.

Okay, so this whole subject is complicated, but it’s still fascinating. Check out the video for yourself:



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  1. If the Universe is infinite, that would mean there is an ifinite amount of visible space and an infinite amount of objects to fill it (Stars and Planets etc…) Since there is space, interspersed with objects that do not touch or bump up against one another there is not infinite numbers of objects (ie totally filling the “space”) Therefore this Universe is not infinite.

  2. If the universe is not infinite then what contains it and what contains that and so on.

  3. This is silly, the universe is expanding, so by definition it is finite.

    • If the universe is not infinite, then there is no such thing as infinity.
      If infinity means never having an end, then what better example could you have than an ever expanding universe?

      • I suspect your understanding the scientific definition of the universe is lacking. The universe started as a single point at the Big Bang. Was it infinite then? How about a nanosecond later? And a second after that? And a billion years after that? The universe is expanding, we have very very good reason to believe that. Hence it must be finite. It is one size now and will be another (larger) size by the time I finish this sentence. Anything outside of the universe is, by definition, not the universe. It may be something else, something infinite, but we can never see or touch it, but it is not our universe.

        • Our universe didn’t necessarily start as “a single point” or even a finite “ball” of energy. It might have, but for all we know the singularity could have been infinite in size. This (the “single point” idea) is a common misconception. The only parts of the universe we can extrapolate back from are the parts we can see, and obviously that’s not infinite, so whatever volume all of it can cram into is going to be finite, too. The singularity is defined by huge amounts of energy in an extremely dense and violent state, NOT “everything condensed into one point,” as you were probably told and as you evidently believe. Again, for all we know the singularity itself could have been infinite in size, which would imply that the current universe is infinite, too.

      • numbers.

  4. Log234, I thoroughly enjoyed your theories. Unfortunately our world may never know the answer to this mystery. To date, only 1 man made object launched nearly 40 years has BARELY reached beyond our own star’s solar system. Unfortunately it is scheduled to run out of power in about 11 years. It will never leave the galaxy. Now, suppose man made an object capable of intergalactic travels…depending on the rate of speed, by the time said object ever reaches the next galactic neighbor and sends signals back to the earth for observation, our great-grandchildren’s great-grandchildren will have perished. Sad truth…c’est la vie. For now, until I croak…it’s star gazing and day dreaming!

  5. The consequenses of an infinite universe are incredible. There would be infinite earths with infinite copies of you, just to ponder one consequence. Reincarnation would be a fact of life.

  6. If the universe is in fact infinite then everything, no matter where it is, is at the centre of the universe.

    • You could also look at it as there being no center of the universe. Everything (especially in physics and astronomy) depends on your point of view.

      Also, it’s kind of interesting that an object can either have one center (most objects), infinite centers (in an infinite universe or in an object where the center of mass is a straight line), or no center at all (an infinite universe). You can’t have an object with two, or three, or fifty-seven centers.

  7. IF it isn’t infinite then what is at the end of it in any direction? A wall???

    • if there was a wall then it would be finite and have an end, infinite means there is no end, there is no stop or line or wall or anything it just keeps going forever with infinite possibilities

      • Yes but Scotia was asking what would be the case if it was finite, not infinite. Btw, Scotia, look at my comment a bit further down, on concept b and/or c.

    • Whats at the end of the earths surface? Is the surface of the earth infinite?

    • Possibly, you find yourself back where you started. As if you’d been walking on a sphere– only in this case, and This is difficult for any of us to grasp, the spherical effect exists in *every direction.* Even straight

  8. 10^35K (possibly) hottest possible temp…..10^-35 Planck scale-where you can’t distinguish between two objects or determine if they are one. The fact that 10^35 keeps coming up, I have decided to make a theory with no scientific research except for those two theories. The universe is 10^35 square meters. It’s mostly fact actually. Thank you.

    • Just wish to point out that the size of the observable universe is 93 Gly or 8.8×10^26 m. So you at least have a larger size than that.

    • Well once the universe expands to about 8,800,000,000 times its current size, I guess we’ll find out whether you’re right.

  9. I think it’s really big!

  10. I’ve compiled some thoughts and logical arguments using what knowledge of the universe I have. There might be flaws in my arguments, for example if my argument contradicts a generally accepted theory that I am not aware of. (as I am not an expert on this field of knowledge)
    So, using simple logic conclusions, this is what I ended up with.

    Before I even can start to consider how large the universe might possibly be; we first have to agree on WHAT the universe actually is:

    a.1) The universe is all that exists: stars, planets, empty space, etc. in this dimension.
    a.2) The universe is all that exists, including all possible dimensions.
    b) The universe is only “stuff” (in the lack of a better term, meaning in this case; anything except empty space).
    c) The universe is a massive loop, so if you fly far enough in a straight line, you will end up where you started. (It might be a bit difficult to imagine, as then the universe would act in another set of dimensions. I will further express my thoughts later in this text.)

    a.1) In case a.1 the universe will be infinite.
    Even if there is a limit with nothing but emptiness on the other side (not like a wall, think of it more like border where the last piece of what we call “stuff” (see definition above) exists), there will always be something on the other side, empty space.
    This argument naturally has its roots in the big bang theory, from which we can draw the conclusion; “Stuff” does end somewhere.
    On the other hand if you are willing to accept there being multiple big bangs going on on different locations in the universe, then the universe could be infinitely large without having the limit of “stuff”. There would be a massive distances between these events, but there would always be another big bang a bit further away.

    a.2) In case a.2 the universe could be infinite^infinite. There could be an infinite number of infinite universes. According to Everett’s Many-Worlds interpretation, every time someone makes an action, whether it’s just a mental choice or they do something physical, the universe splits into the number of different out comes possible for that action. Let me give you a simplified example; If I were to flip a coin, the universe would split into two separate universes, as the coin could either land heads up or tails up (Of course there would be many more splits when you take all variables into consideration). Now imagine this for every single action taken in history and in the future, from big bang to the end of the universe. If you agree with that theory, you would have to accept the possibility of an nearly, if not fully, infinite (and exponentially growing) number of universes. Then, if you agree with the base of a.1 you would have to agree that there could possibly be an infinite number of infinite universes.

    b) Here the universe is finite with the possibility of becoming infinite.
    According to the big bang theory, this way to look at the universe makes it finite, as “stuff” (anything that isn’t empty space) does end somewhere. Now one theory is, as we see the universe is expanding on increasingly high speed, all mass will keep spreading, and if you give it an infinite amount of time, you will get an infinitely big universe. Now, as we don’t know for sure whether it will continue like this, or start shrinking at some point (or just stop), it is a debatable theory.
    If you would agree to the possibility of multiple big bangs going on in different parts of the universe the number of universes could possibly be infinite, but in sections. As b denies that empty space is a part of the universe, you would have multiple separate universes in this same dimension. Some might say that they would all be one big multiverse with the possibility of infinite numbers of universes, making it possibly infinite big. And then depending on whether or not you accept the Multi-World interpretation there could be one or possibly an infinite number of separate multiverses.
    So, the universe could be either finite, infinite, finite in an infinite amount of dimensions, or infinite in an infinite amount of dimensions, depending on which theories you accept.

    c) This way to look at the universe makes it infinite… sort of.
    Imagine that a sheet of paper is the universe, and then you fold it so the ends meet. No matter which way you travel this sheet of paper you will at some point end up where you started. But wait just a minute, you might say, a sheet of paper is only two dimensions, if I were to travel through it, I would simply fall out, that doesn’t fit with the universe, as I can travel anywhere without simply falling out of it. Indeed, and this is where the theory is very difficult to imagine, try to imagine a box where all sides are connected with the opposite side. So if you travelled out the right side, you would travel in the left side, and if you travelled out the bottom, you would travel in the top. This is how the universe looks according to this theory, except that the universe isn’t in the shape of a box (it’s just a lot easier to explain).
    So you could travel an infinite amount of time without ever reaching an “end of the universe”, but you would never get anywhere new, you would always end up where you started.
    So I guess you could conclude with that this version of the universe is infinite, but with a finite amount space.

    I’m not gonna tell you which of these ways to look at the universe is correct. As there is no “correct” way to see the universe. We simply can’t know for sure.

    But I at least feel that a.2 is the one that appeals to how I think of the universe, as well as I like the idea of an infinite number of possible universes.

  11. I don’t know is the correct answer. Human brains are not complex enough to comprehend the scale of the universe.

    • “I don’t know” is correct right now, but it should always be followed by, “but we’ll find out.” The size of the Solar System is too massive to really process, except through models and comparisons, but that doesn’t mean we can’t figure out how big it is, and what things are in it, and what those things are doing. If we gave up on everything that was “too complex” for human brains, we’d still be in the Dark Ages. Hell, we might even still be in the trees.

  12. Typically the argument against why the universe is necessarily finite is that if it were in fact infinite, then there would be an infinite number of stars, and every single point in the sky would be a direct line to the surface of a star. if this were the case, then then space would not look black, but instead would be very bright, because there would be the maximum number of photons reaching us. now i suppose its someone might think that the universe is infinite, but also is not old enough to allow all of the photons to have reached the earth, but im not sure if it really makes sense to say that a universe that is infinite in space, would not also be infinite in time.

    • couldn’t there be black holes and other items producing enough gravity to bend light away from many different tracts of space?

    • To help with the strangeness of imagining a universe infinite in space but not time, think on this phrase: “Everywhere happened all at once.” Assuming our current idea is correct (because of course just like any idea it may be anywhere from 100% correct to absolutely incorrect), the Big Bang wasn’t a specific point in space getting really big all of a sudden. It was ALL of space getting bigger all of a sudden. Mind-boggling and hard to imagine, but true.

  13. Its just really big. I mean size is really only based on perspective right? Try imagining, as hard as it is, through the eyes of an ant.

  14. Wouldn’t an infinitely large universe necessarily require infinite energy? And since we do not see a universe packed wall to wall with singularities, doesn’t this strongly hint that the universe is necessarily finite?

    Doesn’t the fact that the universe is expanding at greater rates over time suggest there isn’t infinite energy? Wouldn’t infinite energy necessarily cause expansion to happen at the fastest possible speed? (assuming there is an upper limit. Has anyone ever published anything on the theoretical limit of how fast the universe can expand?)

    • Infinite mass/energy doesn’t imply infinite density of energy. I’m not sure how you arrived at that conclusion. An infinite space could be full of nothing, everything, or somewhere in between. Also, infinite mass/energy doesn’t imply the universe’s expansion must be infinite, either. The current model holds that the universe’s expansion is partly inertial, left over from the cosmic inflation at the beginning of our universe, and partly due to dark energy. There’s no reason a universe of any size, including infinite size, would have to expand at an infinite speed.

      • I’ve arrived at no conclusion. I simply had ideas based on logic puzzles, unfortunately not mathematical ones as it should be, and started asking questions.

        So where did the energy go then? How do you start with finite energy and end up with infinite results?

        The reverse question as well? How do you start with infinite energy and end up with finite results, where did the energy go? Do I missunderstand the word? When I think of infinite energy I think of a source that is both bottomless in its quantity and as…dense? with work potential as energy can possibly be (again assuming there is an upper limit).

        Why would limitless, measurless power produce finite mechanical results?

        • Well I HAD a really great response to this, but Disqus ate it, so I’ll sum up quickly and simply and hope it still makes sense.
          If we assume the universe is infinitely large, and we assume the universe has infinite energy, that doesn’t mean the energy must be infinitely dense, because all we need to show is that each point in space has an energy value that isn’t zero or negative, and it’ll all add up to infinity since there’s an infinite number of those points. And since there’s energy even in vacuum, and there’s no such thing as negative energy, as far as we know, every point in space does have positive energy.
          To put it even more quickly and simply: infinite doesn’t necessarily mean that every single point has infinite energy, it could just mean that every point has some energy and that the number of those points is infinite.

          • Infinite and finite are two sides to measure space, what if that is a limitation of our mind and there is another dimention to meaure it and that third dimention is to a more superior specie…

          • What you said doesn’t really make sense. To be frank, it sounds like the kind of thing my college roommate used to say after a few hits on his bong. It’s not a matter of perspective, or of evolution, to say that something is either infinite or finite. Either something is limitless, or it has a limit. It can’t be both.

            If you want you can believe we live in a closed universe, and there is no “edge” in three dimensional space but at the same time the universe is of finite size. Think like on Earth, how you can go in a straight line in two dimensions but never reach an edge, because really you’re traveling on the surface of a sphere. Now just raise that up. Some say the universe can be traversed “infinitely” without finding an edge because it wraps back around itself in four dimensions, kind of like how Earth is wrapped up in three dimensions. This may not be true, but we’re working on figuring out whether it is or not.

            But even so, that’s not another “dimention” to measure it with, and it didn’t take a “more superior” species to see that possibility. And a closed universe is still a finite one. Even though you can go in a straight line forever and not hit a wall, there are still only a finite number of objects in it, whether you’re counting galactic clusters or subatomic particles or anything in between.

          • If the universe is expanding then is it infinite or finite?

          • The universe’s expansion doesn’t mean it’s “getting bigger” in the same way a balloon expands and occupies more volume. The expansion of the universe refers to space itself getting bigger. You can look it up for a better, more complete, and probably easier-to-understand explanation, but basically it’s not the size of the universe that’s changing, it’s the size of all the space in it that’s changing. Everything is getting farther apart form everything else.

          • By either description, the universe is finite.

          • Not necessarily.

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