The End of the Universe

(Main Theories on How the Cosmos Will Cease to Exist )

The beginning of the Universe is still not completely understood, although as it is explained in Origins of the Universe there are many theories. The same holds true for the end of the Universe. No one knows how it will end but scientists have deduced a few theories that could shed some insight as to what the future will bring to the Cosmos.

There are many theories for the end of the Universe. Some of these theories actually don't foresee an end at all, but claim that everything is infinite, or even that it keeps repeating. Taking them from the best scientists and cosmologists the following are the main theories for the future of the Universe explained.

The Big Freeze Theory

This theory suggests that if the Universe is either flat or hyperbolic (as in the shape of a saddle) then it fits into the Big Freeze scenario. The shape of the Universe is determined by the density it contains.

As explained in NASA's Universe 101 website, depending on the ratio of the Universe's density to the critical density the geometry of the Universe can be spherical, flat or hyperbolic (shaped like a saddle). A flat or saddled shaped Universe would give way to the Big Freeze end of the Universe. This ending suggests that the Universe will expand forever ultimately making everything too cold to sustain life.

The Big Rip Theory
The Big Rip theory follows the rules of general relativity. It claims that the Universe will continually expand at an accelerated pace until it leads to everything getting ripped and torn apart. "The expansion becomes so fast that it literally rips apart all bound objects," explains Robert Caldwell from Dartmouth University, the lead author of the theory.

This theory puts 'phantom or dark energy', and unknown force, as the the culprit for the expansion and ultimately the 'big rip' of all galaxies, stars, planets, any matter that exists in the universe.

The Big Crunch Theory
This theory is also known as the Cyclic Universe Theory, which is an end of the Universe theory as well as an origins of the Universe theory. Developed by Princeton University's Paul Steinhardt and Neil Turok of Cambridge, it describes how the Universe goes into a series of 'big bangs' and then 'big crunches' over and over again.

As explained in their May 24, 2002 paper "A Cyclic Model of the Universe" in the journal Science, Steinhardt and Turok say this results in the Universe creating and destroying itself indefinitely in a never-ending cycle. This theory model also lends itself well to the concept of the Universe's accelerating expansion due to dark energy.

Multiverse Theory
This theory does not predict an end, but suggests that there are many other universes out there that exist as bubbles along this Universe. Theoretical physicist Michio Kaku explains how this could be possible due to the notion that energy expands faster than the bubble that is the Universe can sustain, thus creating many other Universe bubbles.

There are many different directions that the Multiverse Theory also can go other than the bubble idea, such as Parallel Universes. In this model, linked to the String Theory, it is believed that parallel universes would exist simultaneously to the Universe as it is today, but invisibly residing in higher or lower dimensions that cannot be seen by the human eye.

Of course, this parallel universe is highly conceptualized and there are still many things to be learned by scientists to be able to validate it, but science has proven that they are quite possible. As for the end of the Universe theories, they are being debated and researched and cosmologists will someday be much closer to the realization of how the end will come, if at all.



(source: http://astrophysics.suite101.com/article.cfm/the_end_of_the_universe)