Why is the universe, space and time etc donut ring shaped?
Actually we don’t even know enough about the shape of the Universe to affirm that the Universe is infinite or not. Suppose we put an ant on a infinite sheet of paper. The ant is short-sighted and sees only that close to him his universe look pretty flat. If he starts walking he will never meet a boundary and never come back to the same place again. The two-dimensional plane is infinite and without bounds. Next put the ant on a large sphere. Again our ant can not see far enough to observe any curvature. If he starts walking in one direction he will never come to a boundary, but this time he can make a round trip. The spherical universe is unbounded but finite. We are in the same position as the ant, but in three dimensions. Locally our Universe seems flat and unbounded, but we don’t know if we are in the 3 dimensional equivalent of the plane or the sphere. In the first case the Universe would be infinite, in the second place it would be finite. Now the fun and speculation starts…. Eve
The problem with the donut is that it is – as all illlutrations – misleading because it is a ‘snapshot’ of the universe that is not possible: Relativity says it clearly: The universe can only be seen from the point of reference of the observer in space and time. Anywhere in the universe, in both space and time, we are at the center of it! That’s why Hubble had observed that all galaxies are moving away from us: you would observe the same anywhere in the universe that has no center nor edge: You are always at the center of it. It’s like swimming in the ocean of a planet without continent: you are always in the center of it! Big Bang, Big Rip, Multiverses, etc: we don’t know and never really will. Because … as Einstein said: We can only observe from here and now.
