sure the universe is expanding, and from what i hear, even faster than before. But but our expansion will be short lived. The universe began from an unimaginable mass the size of the period in this sentence by a force powerful enough to set the universe in motion, and for now it (the force) will continue to expand until its momentum stops and we will slowly be crushed back into nonexistence..... unless you believe in the metaphysical......
As near as can be figured there simply isn't enough mass to accomplish this "Big Crunch". That includes the dark mass. It seems that dark energy at one time supplied the push to increase the speed of expansion. Also see Names for the Dark thread.
The fact if the universe is going to shrink again or if it will expand forever depends on the mass of the universe. There is a critical mass wich is 10 H-atoms/m^3 in the universe we can see, about 12 billion lightyears.... The mass that emits some kind of radiation is about 1/30 of this mass, with the mass of the intergalactic gas, it is about 1/20 of this critical mass. What we do know from movements in super-clusters is that the mass of this galaxies all together must be about 20 times as much as the mass we would expect from objects we see and mass/gas we can detect. What is this mass???? When we look at neutrino's (again??) and at their mass, we can guess that mass is about 10^-32 g. But because there are about 150 neutrino-parts per cm^3, the total mass of the neutrino's is about 10 - 30 times as much as the total visible mass in our universe!!!! That means that with all calculations about mass etc. we can conclude the total mass of the universe is almost the same as the critical mass!!!!! Fascinating huh? That means that our universe will have a long period where the the expanding almost stops because of the attraction from mass. Will we accelerate again or collapse?? we don't know. But if it is through that we are accelerating again, that means that we are beneath the critical mass..... (that also means that the universe is much older, with red-shift we don't think about a break where the universe almost stands still...) corrections welcome...
