The End of the Universe

We know how the universe began-- with a giant explosion we call the Big Bang. Using numerous technologies, we have studied the past and current universe. But what comes after? Will the universe continue on forever, or will it explode out of being, just as it came in? We can't determine yet how or if the universe may come to an end, but we can pose a few hypotheses.

The Big Crunch external image Big%20Crunch.jpg

This idea was more popular a few years ago, but remains an intriguing idea. As Edwin Hubble discovered in 1927, the universe is expanding. The power of gravity notwithstanding, everything in the universe is flying farther and farther away. But what if, like the expansion of the balloon it has often been compared to, the expansion of the universe become too much? Like the balloon, once it reaches its limit, it would snap back. In the case of the universe, this would be because gravity has reached some sort of limit, and gravity would cause the entire universe to collapse back in on itself. In this collapse, all the matter would be pulled together into a tiny, tiny spot called a singularity-- which according to the Big Bang theory, is how the universe started. It is possible that after this universe collapses into a singularity, it would explode out again in a Big-Bang-style event, creating a new universe in the process. It has been hypothesized that this may have happened many times, as the universe expands, collapses, and expands again. That could change the meaning of the word 'universe', as the same material would become new universes over and over again.

The Big Chill

As the universe continues to expand, objects get farther and farther apart. More and more, empty space is prevalent. This is because of the expansion of the universe caused by dark energy/matter. The stars will eventually burn out, turning into cold, dead stars or black holes. According to astrophysicist Fred Adams, of the University of Michigan, when the universe is 1 trillion trillion trillion trillion trillion trillion years old, even the black holes will disintegrate into stray particles. These particles will band together once again to create large, atom-like structures, but eventually these too will decay, leaving a blank and featureless void behind. This theory is called "The Big Chill", because everything cools off and dies, and then the universe does not end in fiery destruction, but does nothing at all. This is the dominant idea in cosmology currently.
Even before the galaxies and stars all decay, the universe will be a lonely place for us. Abraham Loeb, a theoretical astrophysicist at the Harvard-Smithsonian Center for Astrophysics, says that the rest of the universe will eventually move so far from us that they will have reached a kind of 'event horizon'. Usually referring to black holes, in this case the term is used to describe the point where the other universal bodies will be so far away that their light will never reach us. We will be left with a frozen image of what they looked like the moment before they crossed the event horizon.

The Big Rip

external image puzzle_cook_big.jpg
This relatively new idea is based on the expansion of the universe. Its creator, Robert Caldwell, claims that the expansion of the universe will continue to speed up and speed up, until it tears first large structures like galaxies, then solar systems and even molecules, apart. It is the exact opposite of The Big Crunch theory. As of this writing, it is not a widely accepted theory, but is nonetheless possible. Caldwell has even come up with a certain timeline for the events:

-- A billion years before the end, other galaxies will have crossed the event horizon and disappeared.
-- Sixty million years before the end, the Milky Way begins to fly apart.
-- Three months before the end, our planets leave the Sun.
-- The Earth explodes just before the end.
-- Thirty minutes later, atoms and their nuclei break apart.
-- The universe ends.

An Ekpyrotic Universeexternal image spacemembranes.gif

Possibly the most far-out of recent theories, this idea was put forth by Neil Turok of Cambridge University, Burt Ovrut of the University of Pennsylvania, and Paul Steinhardt and Justin Khoury of Princeton University. In this theory, our universe is but one of many 'branes' or membranes, floating through fifth-dimension space. The Big Bang occurs not from an exploding singularity, but from the collision of two branes. In this manner would our universe end, as well. While unproven, possibly because of the undetectability of the fifth dimension (we live inside four-- three spacial dimensions and the fourth, time), it is an eye-catching idea. As cosmologist Michael Turner puts it, "It's almost crazy enough to be correct." It's also important to note that this theory does not involve multiple or parallel universes. At one end of this fifth dimension is our infinite universe. At the other is another infinite brane, a universe with physics and qualities unlike ours. In between are other branes, but they are neither infinite, nor universes.


Currently, the Big Chill is the favored theory. Both the Big Rip and Ekpyrotic Universe theories are fairly recent and thus are not yet widely accepted.
However the universe ends, it's a fair bet that we won't be around to see it. That doesn't stop us from being curious about the fate of the universe, as it is our only home.

Bibliography 2002/ekpyrotic.html