Matter and Mutability
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In general relativity, spacetime can be empty of matter or radiation and still contain energy stored in its curvature. Uncaused, random quantum fluctuations in a flat, empty, featureless spacetime can produce local regions with positive or negative curvature. This is called the "spacetime foam" and the regions are called "bubbles of false vacuum." Wherever the curvature is positive a bubble of false vacuum will, according to Einstein's equations, exponentially inflate. In 10-42 seconds the bubble will expand to the size of a proton and the energy within will be sufficient to produce all the mass of the universe
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http://www.braungardt.com/Physics/Vacuum%20Fluctuation.htm