More on the shape of the Universe
I one of my previous posts I postulated that the Universe does not have a 3-dimensional shape, but rather is interconnected with itself in all directions as if it was the surface of a 4-dimensional sphere. The more I think of it, the more it makes sense.
Many people believe that the Universe looks like a three-dimensional, expanding sphere. Before the Big Bang (or Big Bounce) the Universe was all in one spot, then suddenly it started expanding. The problem with this is that this indicates that there is an expanding boundary of the Universe, a shock wave, and that there is an edge. This creates a problem of what lies beyond this boundary. Also the conditions at the boundary would have to be different from conditions deep inside of the Universe, due to the interaction with the outside. I wonder what effect would gravity have on the outlying galaxies. One could argue that since the speed of the expansion is greater than the speed of light or gravitational waves, there would be no difference.
The speed of the expansion of the universe has been reaffirmed in a recent study to be about 73km/s per megaparsec. The farther the object from an observer, the quicker it is escaping. So objects which are two megaparsecs from are escaping at 145km/s from the observer. One could argue that because of this it is not possible to see what is outside of the universe, because to get there one would have to travel faster than light. If the Universe was a three-dimensional sphere, there would be galaxies very close to the boundary. An observer from such galaxy could potentially reach the edge of the Universe without exceeding the speed of light and see what’s outside. Unless the laws of physics were different at the edge of the Universe and for example expansion was faster over there. But so far we found no such evidence and the escape velocity seems to be proportional to the distance from us.
However if the Universe is “closed” and has no edge, no single most outlying point, then nothing can escape from it, there is no energy sink. There is no place in the Universe where one could exit it using conventional means and see it from the outside. There is no outside. This is mind-boggling, but I think it has more sense because it avoids the problem of an infinite space outside of the Universe and possible conditions outside.
Again, in a “closed” Universe one could potentially travel in any given direction in three dimensions in a straight line and would ultimately arrive back at the starting location. In practice, however, this is not testable, because the escape velocity of more distant objects is greater than the speed of light. In fact we can’t even see the entire Universe, we can only see a portion of it, so we can’t even see Earth from very distant times. At least that’s what we think…