Do we live in a finite universe or an infinite universe?

Question

For something to be expanding it must have a set amount of space. Like people say the amount of particles of sand on the each are infinite but they cant be there is a set amount (that increases because of erosion) or else the sand would stretch out forever? Am I right? If I am wrong please tell me why?

Answer 1

The most widely accepted model is that the universe is finite but unbounded.  This is analogous to the surface of a sphere viewed from a nearly two-dimensional perspective.  The sphere's surface has no center and does not have an end.  Yet, it is finite.  Many believe that the universe is like this, only one dimension higher.

Answer 2

When people say that the grains of sand on a beach are infinite, they mean seemingly infinite. Of course they are finite.

Whether the universe is finite or infinite is one of the primary questions in cosmology today. No one knows. Anyone who tells you what they answer "probably" is is lying. All people have are theories with guesses.

Answer 3

The universe is finite but unbounded: you will not find an edge anywhere.  Which sounds a bit weird, and is.  The usual analogy is to a bug on a balloon: the bug may crawl where it pleases, but never encounters an edge.  Now suppose that the balloon is expanding, and you have a plausible model of the universe.

Answer 4

As far as modern physics is concerned it is a finite universe. This is the case for a few reasons, which I can tell you in brief because this format only allows for so much. If you have further questions please email me at [e-mail].

Firstly, it's thought by topologists, physicists, etc. that the universe has the shape of something called a 3-sphere. To make this more obvious, let me give an example. A 2-sphere is the skin of a balloon if you ignore the space that fills the middle of a balloon -- you can only consider the SURFACE of the balloon.

Imagine that galaxies are like points that you draw on the surface of a balloon with a sharpie. Again, we are ignoring the space inside the balloon -- this is important, because a 2-sphere (the skin of a balloon) doesn't have space in the middle. If you can imagine this, then as the balloon expands the points drawn on the balloon will move further apart. This isn't because they are physically moving apart but because the "space" (the elastic) between the points is expanding.

This 2-sphere, the skin of the balloon, has no center and it has no edge. So even though we have all these "galaxies" on the surface of the balloon (the points that we've drawn with a sharpie), there is no center and no edge. This is what Einstein means when he says that our universe is finite but unbounded -- we can measure the finite surface of the balloon but if we travelled in a straight line in any direction we would never reach an "edge" and we could never find a "center."

In the same sense, spacetime itself is finite but unbounded. There is no center and there is no edge according to current thought. The difference is this. Imagine that you are a 2-dimensional bug crawling on the side of a balloon. It's the same in this universe. As a 2-D being on the balloon you are completely ignorant of the 3rd dimension through which you are travelling, which is the direction in which the balloon surface curves.

Likewise, our universe is curved -- but through a dimension that we can't see, just like the bug crawling on the balloon isn't aware of the 3rd dimension through which the balloon curves. A balloon skin is a 2-sphere, our universe is a 3-sphere. Einstein's theory says that gravity is the effect of mass bending space, but when space "curves" it isn't necessarily through the three dimensions we know.

Think of this like a bowling ball on a trampoline. Imagine that the trampoline surface is space, and the bowling ball is the sun. If you roll a ball on the trampoline, it will curve around the mass in the center (the bowling ball) -- this is what Einstein said mass does to space in 3-D.

If you can imagine that you are a light beam, which must travel in straight lines according to Maxwell's equations, when you pass by a mass it's like passing a bowlin ball on a trampoline, and space will be curved in the same way and your path will be bent, even if to "you" it seems like you are going straight.

This curvature is in a direction that we can't see but that doesn't mean it can't exist. To give another example, imagine that you are a line drawn on a garden hose. As you move around the garden hose you can only see left, right, up, and down -- even though the garden hose actually curves in a dimension you can't see as a 2-D being. That's analogous to what current thought in physics is like for our universe.

In short, our universe IS finite, but we know of no reason why it will stop expanding because it's not like rubber -- there isn't a force counteracting its expanding. In fact, as far as we can tell there is a force that is making it expand further. This force, called dark energy in modern physics, is overpowering gravity because instead of getting weaker with distance (like gravity does), dark energy gets stronger with distance, and it seems to push things apart.

Going back to the balloon analogy, it's not the case that there is "really" a force pushing things apart: what physicists interpret this as is actually space ITSELF expanding. If space itself expands then the more distance between objects, the more the expansion will matter! Please email me if you have any questions about any of this and I can clear it up for you. ([e-mail]) I am very friendly and eager to discuss such matters with anyone who wants to talk about it. Thank you.

Answer 5

The universe is definately finite.  From our perspective, we may view it as infinite and can calculate it that way, because, after all, we are fumbling around in the dark.  However, whatever contains the universe, and something has to because everything has a container, is a size and at some point, it will be full.  The universe does have a center, which is close to Earth.  What happens when the universe fills its space?  Simple:  Look at what happens when you fill a pool with water.  If there are objects in the pool, they react, but they eventually work it out.  One day, our universe will be this way... a static place(Not our galaxy, just our universe).

Answer 6

the universe isn't expanding into anything, space itself is expanding.

Answer 7

space is nothingness... the universe is consantly expanding at light speed... no max space....

Answer 8

It is finite but boundless.

There is no outside of spatial dimensions.

The idea itself would lose context.

The standard analogy is to imagine our universe as a balloon that can inflate infinitely.

But the idea that there is room for it to inflate is where confusion can arise.

The universe as an inflating balloon has no limits in terms of how big it can get it will never bump into an outside barrier that prevents it from expanding.

What is meant by finite is that it has a clear point in the past where space/time was an infinitesimally small point that is beyond the scope of human understanding.

Smaller than an atom, where all that is, ever was, ever will be, was an inconceivably tiny speck.

Because of the known laws of the universe the very small size an overwhelmingly huge amount of energy was trapped in a limited amount of space/time, it had no choice but to BIG BANG.

Like god blowing a huge first breath into the balloon that is our universe, and it seems he is still huffing into it to this day.

Note I say god for convenience sake not to suggest that this is how our universe actually got its start.

Answer 9

It is a tricky question and one that science is still wrestling with. As stated, the universe is finite but unbounded.

This generally means that the distance between objects is increasing. But more space is actually "created" as this happens. If you moved in a straight line at near infinite speed, you would never reach any "edge" in the universe. Instead, you would eventually come back to where you started because space-time is curved.

Three dimensional space can be imagined as existing on the surface of a sphere. There is no edge, and any straight line eventually returns to where it started. Since nothing can move faster than light, nothing in the universe will ever be able to make this trip, though, since the universe is essentially "expanding" at the speed of light.

This is obviously hard to imagine cause I asked you to think of three dimensional space as the surface of a shape. The reality is very complex and that is just a handy metaphor. However, if this is how things really are, you can imagine why science has a hard time trying to prove it, understand it, and teach it.