Do black holes collapse? © Getty Images

Do black holes collapse?

These cosmic sink-holes do gradually shrink, but it’s impossible to get any more compact than a black hole.

Asked by: Patricia Rodrigues, King’s Lynn

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The Schwarzschild radius (event horizon) of a black hole is sometimes thought of as the black hole’s ‘size’. It is proportional to mass, which means that more massive black holes have bigger Schwarzschild radii. Left alone, black holes lose mass due to ‘Hawking radiation’, so that their event horizons are slowly shrinking. A typical black hole would take many billions of times the age of the Universe to completely ‘evaporate’ and disappear. But, the interior of the black hole, or its ‘singularity’ (the point at which all the black hole’s matter is concentrated) has already reached the limit of its density and cannot ‘collapse’ any further.


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