This article might give us a way to check for a pre-big bang universe.
In cosmological models based on a theory called loop quantum gravity, our universe has a parent. Loop quantum gravity attempts to meld relativity with quantum mechanics by describing space-time as a constantly rearranging fabric of interconnections. On the smallest scales, around 10-35 meters, that fabric is a tangled mess, but on much larger scales the space and time of our universe look smooth.
The theory predicts that when this fabric is scrunched up, it becomes bouncy. So if the universe before ours was contracting, it would have reached a point of maximum density and then bounced out again in our big bang.
So what would this predecessor have been like? To find out, Parampreet Singh of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, and Alejandro Corichi of the National Autonomous University of Mexico, Morelia, applied the equations of loop quantum gravity to a highly simplified model of the universe. They found that the properties of space, such as the quantity of matter and energy it contains, hardly change when the universe goes through the big bounce. "For the simple model considered, the universe is almost exactly the same on other side," says Singh.
It raises the possibility that we could see an imprint of the universe before ours. Singh suggests that the seeds of large-scale structures in our universe, such as superclusters of galaxies, would have been present on the pre-big-bang side. The pattern of those seeds might be preserved in the cosmic microwave background radiation - the relic radiation left behind by the big bang. "If this conclusion holds true, then it is possible that we are going to see signatures of the pre-big-bang universe," says Singh.
Did pre-big bang universe leave its mark on the sky? - space - 10 April 2008 - New Scientist Space
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