# How come that an Infinite universe will collapse under gravity?

In this PSE post the issue is about the stability of an infinite universe under Newtonian gravity.
Here I'will drop the Newtonian constraint because we know of the finite speed of interactions and I ask :
How can someone explain the existence of a gravitational collapse ?

In the drawing the universe is isodense and infinite and it will extend outside of the limits of the screen ;)
The grayed spherical regions represent the observed universe in relation to the points A,B,C (that can be considered as centers of the universe) and the three points are causally disconected because it is impossible that the interactions had time to propagate from A to B , ... to the entire universe.
You can imagine a similar region around the point X that can see both A and B.

Because nowhere exists a gravitational gradient, whatever the density, there is no chance of motion whatever the selected point. IMO.

How can someone explain the existence of a gravitational collapse ?

• Does noting the non-uniform mass density of our universe have bearing on your question?
– BMS
Apr 19 '14 at 6:15
• @BMS non-uniformity reported in what observations? I forgot to add isodense ;) as observed. Apr 19 '14 at 6:39
• some will be tempted to point that FRW eqs show that it can grow/collapse at will. That is out of focus because they posit: It also assumes that the spatial component of the metric can be time-dependent. No wonder that under this additional injection the eqs will have to show whatever we wish. Without this additional constraint the universe will not collapse. Thats my point. Apr 19 '14 at 21:27
• Since I posted the question I got two downvotes elsewhere without any comment, as usual. Arguments are much more difficult than downvotes. Those esteemed downvoters did not realized yet that I do not care about that. Please use some arguments. I do care. Apr 19 '14 at 21:59
• I can only guess why people are down voting this question, but I find it enormously unclear. I suspect that you have a big structure of interconnected ideas in your head and that this might make sense in the context of those thoughts, but no one in your audience is coming from that perspective. This is a common problem in technical writing especially where there is pressure to be concise. Apr 19 '14 at 22:26