# Are we moving away or towards each other?

There are numerous theories about the shape of the Universe. I've read somewhere most probably in 'A Brief History of Time' that there is a possibility that the Universe is spherical. So is it possible that all galaxies are moving towards each other? Imagine the Universe as a sphere. Now, imagine a diameter AB. The Big Bang took place at A and the galaxies started drifting away and as they moved away further they stared attracting each other on the other side i.e.Gravitational attraction. So we feel that the farther galaxies are the faster they are moving away(Hubble's Law) but actually they are moving towards each other and will eventually meet at point B. Also, space-time is spherical and so light travels along the sphere.

So, my question is: Is it possible for the universe to be spherical with galaxies apparently moving away but actually moving closer?

• All your reasoning is based on wrong bases. A spherical Universe does not mean that the Universe has the shape of a soccer ball. It is a way to identify its geometry, not in our common sense. Commented Mar 23, 2014 at 9:02
• Then what exactly do we mean by a spherical universe? Commented Mar 23, 2014 at 9:46
• Take a look at here starchild.gsfc.nasa.gov/docs/StarChild/questions/… Commented Mar 23, 2014 at 9:53
• @Py-serThat was very useful and lucid. It also says that a spherical universe means that there would be a Big Crunch. Then can you please point out where have I gone wrong? Commented Mar 23, 2014 at 10:08
• Take a cylinder and slice it. Depending on the plane of the slice you get a rectangle, a circle, an ellipse, or an ellipse intersected with a rectangle. You may think of the universe as a 4-dimensional curved surface embedded in a 5-dimensional hyperspace. Depending of how you slice it, you'll get different results. If you slice it along a fixed cosmic time, you'll probably get a giant 3-sphere, the surface of a 4-dimensional ball. If you slice it parallel to the cosmic time axis you may get a shape similar to a hyperboloid or a paraboloid with time as symmetry axis. Commented Mar 23, 2014 at 14:33

## 1 Answer

At the present time this doesn't hold for the observable universe, since the observable universe is only a tiny fraction of the surface of the 3-sphere (assumed it's a sphere at all). The observable universe is flat within a 0.4% error.

Based on this, we are moving away from each other. And the universe is expanding. So even if it would be curved, we would move away from each other. Only in a future Big Crunch scenario, we would eventually move towards each other.

Finite flat cyclic spaces can be constructed, but there is no significant hint, that the universe is of such a shape, or any other non-trivial topology.