Since the universe is expanding, it, therefore, has a finite area. What happens when my space ship hits the edge of the universe? Does it bounce back and an astral voice instructs me not to pass the universal edge and do not collect $200?Also, what is outside the edges of the universe? More space?
First, you should say “if” the universe is expanding. True most cosmologists think that it is due to the change in light from objects they track (red shift), but it is a theory.
That said, I think they would say that (if it is true) you could never reach the edge because the distance you have to travel to reach the edge–from the edge minus x miles–is expanding faster than you could travel. I think I recall reading that the theory also states that the further you get from the center of the universe the greater the rate of expansion.
I’m sure others will have better informed input.
I stand corrected, since we are dealing with the Big Bang ‘theory’. But, theoretically, if something has an ‘edge’, it is obtainable. Not necessarily by inhabitants of Earth, but by something/someone.
Centers, edges, and outside are not defined terms with respect to the geometry of the universe as an object.
The center of the universe is everywhere, and the edge is pretty much “Very Far Away” from the center. The outside has not yet gained the characteristic of dimensions, including duration, so it hasn’t been a what yet to be defined as being outside, or a direction in which to have been outside of anything.
I hope this helps you.
Tris
Given that the universe is either infinite or just really, really big, it’s not really expanding in the sense of, say, a balloon. It’s just getting less dense, the objects within it are getting farther apart, so from the inside, it looks like it’s expanding. But you run into trouble when you ask what the universe is expanding into, in which case the answer is nothing, because the universe is everything.
According to my physics teacher in college, if you go far enough in one direction, you end up where you started.
I gather that the idea would be similar to, if you were to draw dots (stars) all over a balloon (the universe) and then start filling it with air–the dots will all get further from each other and the overall surface area expand, yet if you travel in any direction along the surface of the balloon, you will never hit the edge.
To get “outside” of the universe you’d have to be able to travel in more dimensions than it contains. Let me know when you figure out what’s there, it’s worth a Physics Nobel.
The standard explanation is that the universe is like a balloon, and we live on the surface of it. The expansion is due to the balloon being blown up, so while things are getting farther apart, there’s no edge for us.
I think this premise is false. Why can’t you expand an infinite universe?
The way I’ve always heard it is that the universe is finite, but unbounded. There is no edge.
You can. It’s not very intuitive, but it could have been infinitely big to begin with, and every point in it just got bigger! All we can say for sure in the simplest terms is everything started out hot and dense, and got less so.
Loopydude if you’re addressing that to me, I know that. I meant to point out that the OP is based on a false premise, therefore no valid arguments can be made based on it. It’s not difficult but to see why it’s false the Hilbert Hotel “paradox” helps.
Actually an expanding universe would be the same as if evey object in the universe got smaller.
Would that mean you’d have to start out with extremely huge subatomic particles? As they possibly have no dimension now, how would they go from humongous to possibly zero dimension in a finite time?
No. I was saying that an expanding universe and a constant size universe with everything getting smaller are two wayw of describing at the same thing.
I guess by everything getting smaller, you mean everything. If not, I guess I’m still a bit confused. For instance, if I left space a constant size, and just shrunk a star, unless I also shrunk its mass/energy, it would collapse into a black hole. But, if I shrink its mass/energy to keep it from such collapse, it’s not massive enough to create the kind of pressures due to gravity to maintain thermonuclear reactions, and it goes dark.
As things are, space gets bigger, but objects residing is space stay the same size. Or so I thought.
A couple of links tothe Cornell astronomy pages relevant to this discussion:
What is the Universe Expanding Into?
Is the Universe really like an expanding balloon?
All part of a wonderful Q&A site about cosmology at Cornell
The expanding balloon analogy can be useful, but it shouldn’t be carried too far. The balloon analogy describes a universe which has a finite size and positive curvature, and as of a few years ago, this seemed to be a viable possible description of our Universe. In such a universe, one could, in principle, end up back at one’s starting point by travelling far enough in a straight line, much like one can sail around the Earth.
Current evidence, however, seems to indicate that the Universe is flat (or very close to it), and the simplest assumption is that it is therefore infinite. At the very least, it’s certain that the Universe is very large, large enough that it would be impossible to fly completely around it. And even if the Universe is finite (a possibility which we can never rule out), it still doesn’t have an edge, and every point in the Universe has an equal claim to being the “center”.