When they made their discovery, Calmet and his University of Sussex colleague, physicist and astronomer Folkert Kuipers, were performing calculations using quantum field theory to try and probe the event horizon of a black hole.

Specifically, they were trying to understand the fluctuations...

Not much pressure, to be sure – but it's a finding that's fascinatingly consistent with Stephen Hawking's prediction that black holes emit radiation and therefore not only have a temperature, but slowly shrink over time, in the absence of accretion.

Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter in an object.

The largest black holes are called "supermass...