Question: Once the universe reaches max mass will it implode, (your thoughts)

Mark Mirmelstein answered on 6 Mar 2018:

As far as we are aware, the law of conservation of mass holds in our universe, so new mass does not enter our universe. However, there is much we don’t know yet about our universe, like what is our universe expanding on, which may prove that mass does flow into our universe, and perhaps doesn’t flow out. If indeed a lot of mass ends up in our universe, it will mostly mean we will have a lot of black holes around, but perhaps by some unknown mechanisms it will collapse. There is much we need to understand about our universe to answer such questions.