Thread:Comments:Scientists conclude that the universe may expand forever/Curses!/reply (3)

Dark matter (which contributes to a potential Big Crunch) is unrelated to Dark Energy (which contributes/is the accelerating expansion of the universe). Generally the evidence for either is empirical; we're still figuring out the math to find the rest of their influence and how they work... we're still working on the theories (i.e. theoretical evidence).