I read that the mass of the universe slows the expansion of the universe. I also heard that if the mass of the universe was above a critical value the universe would contract. I believe this is called the big crunch scenario. And that it is currently not considered a probable scenario. Is this true? I have some follow up questions if this is really true. The next question is what do we understand by space contraction in the big crunch scenario, Does this mean the mass then goes to the center of the universe but the piece of space I am currently sitting in is in the same place after the big crunch, or has the space also actually moved so that it is at the same point as the me? ( of course under the condition that a big crunch happens and I live that long and i don't move in space - Neither very likely I know, but anyway.