Monday, May 22, 2006

The Universe Before It Began:

Using a theory called "loop quantum gravity," a group led by Penn State professor Abhay Ashtekar has shown that just before the Big Bang occurred, another universe very similar to ours may have been contracting. According to the group's findings, this previous universe eventually became so dense that a normally negligible repulsive component of the gravitational force overpowered the attractive component, causing the universe to "bounce" apart. This big bounce is what we now know as the Big Bang. The group published its analysis in the April 12th issue of Physical Review Letters.


Loop quantum gravity also predicts a small repulsive component of gravitational force, which is a non-factor in other theories. At most densities, even the extremely high density of an atom's nucleus, this component has no significant effect. But as density increases, approaching 1075 times the nuclear density, this repulsion begins to dominate. According to the Ashtekar's equations, this appears to be what happened to the universe before ours: As it collapsed, it became so dense that gravity started to, in a sense, work backwards, birthing our universe.

Singh, Ashtekar's postdoc, noted that the group's conclusions are eerily similar to findings published by Princeton researcher Paul Steinhardt two weeks ago. Using string theory, Steinhardt concluded that the universe may be cyclic, with each crunch leading to a bounce.

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