If this boggled your mind as a kid, then you’re in good company, because it boggles the minds of most scientists too.
The thing is, the universe doesn’t expand in the way that our brains are used to thinking, from some kind of central point. It’s more that every point is space is getting further away from every other point in space.
That is, from your perspective, everything is moving away from you, but everything is also moving away from a person in China, or on the moon. You would never be able to located the central point of expansion (because it’s everywhere) and there fore never be able to locate the “edge” (because there isn’t one).
A simple way of answering the question is that the three-dimensional universe is expanding into four-dimensional space. Simple, but not necessarily easy to comprehend.
A good way to think about it is to scale it back a dimension. Imagine that you are a two-dimensional being on the surface of a balloon that is being inflated. From your perspective, every point is moving away from every other point on a two-dimensional plane, but the balloon as a whole is actually expanding into the third dimension.
Now scale it back up to the third and fourth dimensions. In order to find the “edge” of three-dimensional space, and therefore get a perspective on the expansion of said three-dimensional space, you have to be able to enter the fourth dimension.
This would mean that you would have to find a direction of travel that was not up, down, left, right, forwards or backwards.
kharshad1 