Why should space-time have an overall shape?

Question

such as being postively curved (like a sphere), negatively curved (like a saddle), or flat (like a perfect plane)

Answer 1

Why..? Because the physical conditions as set at the instant of the Big Bang, mainly the strength of gravity and the amount of mass, were such that the geometry of our universe is 'flat.'

Answer 2

Why do you think it would not?

If it is real and physical, it must have dimensions of some sort. Once you say that, space-time has a shape, even if it is not constant. No matter what convolutions you claim, no matter whether it is shaped like a perfect sphere or a nightmare of a porcupine, if it has dimensions, it has shape. Saying one says the other.

Space time in a given region is theorized to be distorted by gravity. So shape might well be governed by nearby stars and/or black holes and all sorts of stuff in between. Between galaxies, where stars are VERY few and VERY far between, there is no gravity to distort space-time so it can be much flatter.

Answer 3

Shape is a human term to be perceived with your eyes. You need to ask yourself how many dimensions you believe space-time actually has. What we do is to take the many dimensions we know that it must have and project them onto a 3-dimensional plane where we can physically perceive it because we only know the 3 dimensions. Try telling your computer screen to work in 3-dimensions. It actually can't, what it can do is project what it feels the 3-dimensional image is onto its 2-dimensional surface. This is why space-time has a shape, because we as humans project it in such a way that we can understand and interpret with our brains.

Answer 4

I agree with you...Why should it have any shape at all, and why are folks so concerned about that?

On the side bar to Yahoo Questions and Answers there should be a column of fixed answers we could refer to
as in "See Answers 17a and 17b."

Space is infinite
as far as we know.

Space has no shape
as far as we know.