From George Keeling, Berlin, Germany
Have I missed something? Surely this is big news: Jon Richfield describes black holes losing significant mass (Last Word, 7 October). I took the trouble to read the paper on the detection of the black hole collision by LIGO and Virgo (Physical Review Letters, ). The black holes had masses of 30.5 and 25.3 times our sun's, and the resulting black hole had a mass 53.2 times bigger. So about 2.6 solar masses were radiated as gravitational waves.
It was a well-known rule of black holes that neither matter nor energy can ever escape them (bar a whiff of Hawking radiation). It now seems that there is a way out after all!
The editor writes:
• The “missing” mass/energy was indeed radiated away as gravitational waves. But that isn't due to mass escaping from a black hole – it comes from the potential energy in the positions and spins of the two black holes.
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