**Under certain extreme ****conditions**** Einstein’s general theory of relativity seems to violate determinism, according to an international team of physicists. The group has shown that in a universe expanding under the influence of the cosmological constant, black holes generated by the collapse of highly charged stars should contain a region where physical conditions are not fixed by the stars’ initial state. At odds with a 40-year old idea known as cosmic censorship, the researchers say that signs of this indeterminism might show up in detections of gravitational waves.**

**Newton’s mechanics allow us in principle to calculate the exact state of a physical system at any point in the future, provided that we know its initial state perfectly. So too with general relativity: a precise knowledge of space’s geometry and its rate of change in the present enables us ****in theory**** to predict exactly how space-time will evolve. As such, Einstein’s theory is considered by most physicists to be entirely deterministic.**

**Charged black holes, however, challenge this deterministic picture. The “Reissner-Nordström” solution of general relativity describes a black hole created when a star that is electrically charged and spherical collapses in on itself under the force of gravity. Hidden from view inside such a black hole’s event horizon lies a second boundary known as the Cauchy horizon, beyond which space-time is smooth but indeterminate. In other words, the future can no longer be predicted.**

Category: Science

Written by Kim Burrafato

Published on Monday, 29 January 2018 10:49

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