Follow the Bouncing Universe

"Follow the Bouncing Universe" by Martin Bojowald (Scientific American, October, 2008).

This article is basically a review of some current research on "loop-quantum gravity" and on what might be called an "atomic theory of gravity."

There are two really good elements in this article, while most of the rest is just a survey and review.

1) The article describes the possibility, now being studied and thought upon, that gravity is not a purely attractive force. The idea is that gravity actually attempts to force quantum particles to be a specific distance apart. Further than this distance, it acts as an attractive force. When the sub-atomic particles come too close, though, gravity "flips" and acts to push things apart. In this idea, the big bang was an event which was caused by the density of matter in the universe being very, very high (100 billion suns in the space of a proton). At this density, the universe literally exploded. Gravity quickly began acting as an attractive force, and the expansion of the universe is just due to the "momentum" achieved in the initial explosion.

2) Another insightful element of this article was the metaphor of the balloon. One logical corollary to the hypothesized system of quantum gravity, described above, is that the universe could have actually "flipped" inside out. If you imagine a series of events with bang bang like explosion, followed by a contraction, following by an explosion, etc... it becomes conceivable that the universe actually turns inside out at the end of each contracting phase.

Imagine a balloon, blown up. Imagine the air all coming out of the balloon. Now, instead of simply lying limp and empty of air, imagine if, when the last bit of air came out, the balloon turned inside out and blew up again. You can also imagine this by thinking of a balloon attached to a hole between 2 walled-chambers. Imagine the pressure going up in one side and down in the other side, and the reversing, causing the balloon to inflate in one direction, deflate, and then inflate in the other direction.

Another interesting thing about these theories is that, as one can see from the balloon metaphor, it is possible that information could be preserved from one "side" or direction to the other. Not much information would be preserved, but it is possible that, say, some air particles would not be compressed to a singularity (a point at which information is lost), and how they flowed through the aperture (the balloon) would impact particles on the other side.

On the other hand, another way to interpret the metaphor is that no air could ever pass from one "side" to the other. Unless information could be "passed through" the membrane (balloon) without it actually being permeable to air, there might be no meaningful communication between the two sides. In this example, information might be preserved, not from the "last" universe before this one, but from the one before that.