One of the more popular analogies of the structure and formation of the universe is an expanding sphere, with what we se as the observable universe being the surface of that sphere.
I believe Einstein once stated that if one had a spaceship and went far enough in a straight line, one would end up right back where he started from: this is analogous to circumnavigating the globe.
Like the old Atari video game Asteroids. :rolleyes:
Is it possible, in theory if not in fact, to point a telescope into one point at the sky and view a distant galaxy at the edge of the observable universe, then turn the telescope 180deg. the opposite direction and see the same galaxy from the other side?
It is possible in some theories. If the universe is closed it may be something like a 3D sphere embedded in a higher dimensial space. Or it could be connected in other ways. Look for things on “topology of the universe” For exampe: http://luth2.obspm.fr/~luminet/etopo.html
I’ve heard the same theory. It doesn’t mean that’s a difinitive answer - just a theory.
Here’s the quick and dirty analogy. A bug lives in 2 dimensions. It doesn’t know about up and down (z axis) only left/right (x-axis) and forward/backward (y-axis). His little bug mind makes up a theory that his universe (planet Earth) is spherical and that if he continues to walk in one direction, he will get back to where he started. His theory is sound, but he can walk his entire lifetime and not even get close to where he started. And since he lives in only two dimensions, his feeble bug mind can’t even comprehend the 3rd dimension - which is the dimension he’d have to travel to leave his universe.
The same thing holds true for us. We can travel to the extent that our technology will let us in any of our 3 dimensions, but we’ll never make it back to where we started. And, to get out of our universe, we would have to travel in a dimension that our feeble human brains can’t comprehend.
I’m not stating this as a fact. Just a theory that I heard.
The bug might also be right about there being only 2 dimensions, which wrap around, with no external up/down needing to exist at all. As in the OP’s example of Asteroids. Though Asteroids is at least Euclidean on sufficiently small scales, which the bug’s world is not.
It’s theoretically possible. However recent observations have largely ruled this possibility out. Basically physicists surveyed the cosmic microwave background radiation and looked for statistical patterns that would indicate that they were seeing overlapping distribuations of radiation in different parts of the sky. They didn’t see the patterns, so it’s fairly certain that the universe is bigger than the part we can see.