Is space Infinite?
IANAC
No. If you travel x amount in one direction you will end up where you started. Unless I misinterpreted something I read. You may want a second opinion.
Nobody really knows, do they?
Thats only if the vaccum of space is round though right?
I’d like to think that you could never run out of space. Things would just go on and on forever. What was not there when you get there becomes new space.
for practical purposes yes, because the latest estimate is that the size of the universe is expanding many times faster than the speed of light.
The current best estimate is that space is flat, though it’s not really possible to distinguish between “flat” and “spherical (or hyperbolic) with extremely large radius of curvature”. And even if it’s flat or hyperbolic, it would still be possible for it to be finite if it had a nontrivial topology. We haven’t detected any evidence of nontrivial topology, but that just means that the identification scale isn’t smaller than the distance we can see. It could still be identified on some larger scale. Put it all together, and the conclusion is unambiguously that we don’t know, and even if it is infinite, we would never be able to prove it.
What do you mean by “what was not there when you get there”? There’s no edge.
If space is expanding then it has to have an edge. Even if it is only for the split second before the new space is created.
Balloons can expand without having an edge.
No they can’t. The edge of the balloon is wherever the outside happens to be located. All objects with volume have an edge.
I think he means the surface of a balloon can expand without having an edge.
Second opinion. The geometry of space can take three configurations. It can be positively curved, negatively curved, or flat. Current thinking is that space is essentially flat. For a straight line movement to end back where it started, space would have to be a certain type of positively curved. So that probably isn’t true unless our understanding and measurements change drastically.
The biggest obstacle to understanding anything in physics and mathematics is common sense. We live inside space, and inside three spatial dimensions of space (plus one of time). That skews our senses and our perceptions. The physics of extremes - big, small, hot, cold, infinities - doesn’t conform to common sense in almost any way.
Take a balloon. We see balloons as three-dimensional objects, with an inside of air, a skin of mylar, and an outside of more air. Mathematically, however, we can abstract the skin to a two-dimensional spherical geometry. There is nothing in this universe except the skin. No air. No inside or outside. Just infinitely-thin mylar. In such a world it’s obvious that no edge exists. When the mylar expands, there’s just more mylar. It’s not expanding into anything, because there isn’t anything else. Mathematically, this two-dimensional space is as accurate and reliable and predictable - and right - as any other mathematical object or structure.
Space is the three-dimensional equivalent of that mylar skin. There is no inside to space. We live in space, but space is everywhere, including inside us. We are part of the “skin” in that way. There is no outside it. By definition space is everything there is. So when space expands it doesn’t expand **into **anything. It just gets bigger. There is no edge, either, any more than the skin of a balloon has an edge. There is more space. And that’s all you can say. That may not be common sense, but it is perfect math, and the only math there is.
And there are analogs of this for every dimension. It is absolutely not true that all objects with volume have an edge.
Almost all the questions we get from people who don’t understand QM or want to dispute relativity or think that 0.9999~ is not equal to 1 comes from this basic application of common sense to math, where it doesn’t belong. You have to get over that. A huge hurdle, I know. And I don’t know how to advise you to leap that hurdle, except with an “a-ha” moment. With luck, some of these explanations might someday help.
Reiterating what **Harpo **said, and suggesting that you check out The Fabric of the Cosmos, a PBS series within NOVA that you can watch on the website I just linked. Also, if you’re inclined, read the book.
There are lots of excellent ways presented to think about infinite space expanding, and, in fact (as of the book’s writing), an infinite flat space, expanding in accordance with Hubble’s numbers, is the leading model for what the universe’s space is ‘shaped’ like.
IANAScientist, but It’s my understanding that ‘space’ was quite small at the time of the big bang and is getting bigger and bigger. Now, it may be expanding at a colosal pace, faster than anything in the universe, but that does imply that it has edges and is therefore not infinite.
It only implies that if you use the common English meaning of the word “expansion”; in this context, the word is shorthand for something much more complex and implies nothing of the sort.
A lot of scientific concepts get boiled down to simple soundbytes for the public to consume; this is not the science, though, it’s just a soundbyte. The actual science which “expansion” is short for is hundreds upon hundreds of technical papers containing very long equations and observations. It’s not intuitive (the universe simply isn’t, much as we’d like it to be) and we find it very, very hard to express in non-mathematical terms. So we use words which people take a little too literally, but there is no better word that we have. So we have to make do.
We can try to use analogies like the balloon one above; but because these are only rough analogies, they are obviously flawed. Once should not mistake a flaw in the analogy for a flaw in the science the analogy is trying to dumb down.
You’ve spotted a weakness of the English language, not a scientific revelation. 
Space was not small at the time of the Big Bang, though that’s unfortunately how it’s often reported in popular media. Space was dense at the time of the Big Bang. Our observable universe was small, but that’s all we can conclude. No one has any clue how much bigger the universe is than our observable portion of it, and it very well could be infinite.
I never heard this until it was mentioned several times recently on the SDMB by knowledgeable people.
I had always understood that the Big Bang Theory posited a very small universe at the very start. Not just very dense, as you are saying now, but tiny.
Can I ask you, is this a new way of thinking? Or has it always been part of the Big Bang Theory that I have consistently misunderstood?
I am a bit mystified because I have read numerous popular science books on this subject over the years and somehow missed this very important point.
But if it has an edge, then what is on the other side, and how far do you have to go to get to the edge of that? And what is on the other side?
Does your brain hurt yet?
The latter. For a universe that is flat or hyperbolic, the model has always been that the size was infinite, with a density that diminshes with time. For a closed universe, the story is different. In that case, at any given point in time, the universe has a finite size. If you extrapolate back to zero (the singularity), the size is zero. Of course we can’t extrapolate all the way back, because the current laws of physics can’t explain the singularity itself.
Space can be flat and still be finite, without boundary.
To see how this is possible, I will start with a two-dimensional flat space without boundary. You normally think of a torus as curved, but it can be given a flat geometry. One way of thinking about this is as a square with the top and bottom edges identified (thought of as identical) and the right and left edges identified. Now do the same to a three dimensional cube with the front and back face identified, the left and right face identified, and the top and bottom face identified. (I hesitated whether to say face or faces in this description. The English language is not quite up to describing this situation.)
If you have ever played go on a toroidal board you will understand what I am saying. There is an instance of the smallest safe group that consists of 10 stones arrayed in the proper configuration using all four corners. There is no safe group with fewer than 10 stones, since the board actually has no edges or corners. Finite but without boundary. A hyperbolic geometry necessarily has finite volume, but it could have infinite extent. A spherical geometry has finite extent but no boundary.