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, doi.org/cd7d). 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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