Our Universe may have a twin. Li-Xin Li of Princeton University in New Jersey has calculated that our Universe and its sibling could be akin to two soap bubbles connected by a thin tube. "To an observer situated far from the connecting tube, the interior of a bubble would look just like our Universe," says Li. To find out what our Universe may be like, physicists look for mathematical solutions to Einstein's equations of gravity. Li has found an exact solution that predicts a pair of low-density, or "open" universes. The discovery, he says, was "very surprising".
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