Numerical simulation of two merging black holes
Credit: Werner Benger

Gravity's Echoes?

Black holes are regions of space bounded by an "event horizon" beyond which nothing can escape. Any object or signal of any kind that passes through the event horizon is forever removed from communicating in any way with the surrounding Universe, according to Einstein's theory of gravity. Einstein's theory also predicts the existence of gravitational radiation, waves in spacetime produced by the acceleration of mass. The direct detection of gravitational radiation from merging black holes by the Laser Interferometer Gravitational Wave Observatory (LIGO) was spectacular confirmation of Einstein's predictions. This discovery also opened an entirely new window on the Universe and allows important new tests of our understanding of the structure of the event horizon - whether it's described by the relatively simple idealized spacetime of General Relativity, or if it's a seething region of "firewalls" or "fuzzballs". A new analysis of the LIGO merger events detected so far seems to suggest that strange things may be afoot near the event horizon. A careful study of the LIGO signals seems to have found evidence of "echoes" of the gravitational wave signal which are apparently reflected somehow from the horizon - something that wouldn't be allowed by General Relativity. If true, this may suggest that black holes are surrounded by a firewall of high-energy particles, a direct contradiction of general theory. Was Einstein both wrong and right?
Published: December 19, 2016

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Page Author: Dr. Michael F. Corcoran
Last modified Tuesday, 27-Dec-2016 10:22:05 EST