The Big Crunch, though it should be called the
Great Crunch as per the fact that the
event will not be large - but indeed quite great - but will appear to a disembodied
observer to be the convergence of all
matter and
space-time fabric to a single -zero dimentional-
point. There are a
number of suggestions, speculations, and provable theories which explain this phenomenon, but I will only go into the three most popular - and the three that make the most sense.
- The Great Crunch will be caused by the universe -(Organ Universe)- ceasing to expand because the gravity generated by the mass of the universe would overpower the intertia of galaxies, clusters, etc... and the universe (Organ Universe) would begin to contract toward itself and end up turning around and crunching (Great Crunch) into itself at a single point. It is thought that the kinetic energy of this event will spawn another Big Bang and the cycle will continue. This concept of the Great Crunch relies on the critical mass of the universe being large enough to pull everything back unto itself. If one adds all observable matter, one finds that it is short of critical mass for a Great Crunch by a factor of almost 10. The answer to this problem is mass called dark matter, matter that is just like regular matter (if there is such a thing) exept that it cannot be seen. Its effects can be seen everywhere we see gravitational forces working but we cannot see the matter that would make such bends in space-time. Several explainations of dark matter include burnt out stars, neutrino clouds, and all sorts of things that make sense, solve the problem of critical mass, and have observable effects on the universe.
- Another view on how the Great Crunch might happen is if every galaxy, matter cloud, and speck of mass are moving away from eachother, then eventually - regardless of the critical mass and dark matter ideas - they will go full circle around the universe. Relativity explains the space-time fabric as unbounded but also as finite; this means that it is curved- somewhat like a sphere. So eventually all matter will travel a full course and end up in the same place it all started - thus, a Great Crunch, the same kinetic energy and the possibility for another Big Bang.
- Another -though unpopular but acceptable- idea is that matter (galaxies, or matter clouds) will start to move toward other pockets of mass which make larger bends in space-time. Eventually, it is thought, the little pockets of mass will collide with the larger pockets and so on and so forth until all mass collides and the resulting warp in the fabric of space time will tear a hole at a single point, and blah blah woof woof, etc... you get the idea
What exactly does this mean? "The result indicates that the universe if flat." I find myself acutely confused; wouldn't such a simple CMB probe disproving Relativistic concepts of space-time curvature make headlines and cause a massive disturbance within the scientific community? And as for the matter discrepancy, MACHOs, neutrino mass, and plain ol' dark matter make up for it more than adequately. Please ladies and gents, explain further what you mean, i'm curious? Did some hodge-podge NASA experiment negate relativistic concepts of spacetime curvature?