Mass and time dialation

[ajb]

When you look at a simple Minkowski diagram, you may notice that there are regions of spacetime that are causally diconnected from us while very close. The left & right part of the diagram are evident examples.

 

We are thinking about connectedness as topological spaces, have a look at the Wikipedia entry.

 

Loosely, a connected space is in one piece as maybe in many separate pieces.

 

If the universe is not connected (there are several technical refinements of this notion) then our Universe lives on one of the connected components, i.e. one of these pieces. However, these other parts of the universe cannot effect our Universe, so there existence is rather a philosophical question.

 

I bring the notion of connectedness up as I have no idea what the "fixed point" of the universe is! It could be a single disconnected point, but this would have no real bearing on our Universe!

[michel123456]

Oh, that was the connected.

 

I ment something different.

Contrarily to intuition, something that is on metre away from you and in your present, is not causally connected to you. Because time is needed for any interaction to happen, bodies in mutual present are not causally connected.

 

So what I say is that one metre is pretty close for something "disconnected", there is no need to look at far away galaxies.