Could a black hole ever die? Yes, black holes can die, but in a very slow and mundane fashion.
Empty space isn’t actually empty. Although it contains no mass or energy, the ‘quantum fields’ that define mass and energy still exist. These fields, because they’re not required to have zero energy, can create pairs of ‘virtual particles’, normally a particle-antiparticle pair, which quickly annihilate each other.
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But, according to the usual explanation, near a black hole, it’s possible for one of those particles to disappear inside the black hole, while the other one escapes as ‘Hawking radiation’.
To conserve the total energy of the black hole, the infalling particle must carry ‘negative energy’ (and hence ‘negative mass’) and the escaping particle must have positive energy.
Hawking radiation is the result of how gravity affects space-time. The quantum fields in empty space obey Heisenberg’s Uncertainty Principle, which means there’s a limit to the certainty with which we can know their energy, or the time at which a specific energy can be assigned to them.
Since a gravitational field bends space-time and affects the local passage of time, this means that regions of space-time with different gravitational curvatures cannot agree on the energy of the quantum fields.
It’s this difference in the energy of the vacuum at different locations in the gravitational field of a black hole which creates the so-called ‘virtual particles’.
The escaping positive energy from a black hole gradually reduces its mass and energy. So black holes that aren’t actively sucking in new material will slowly shrink and ultimately vanish.
The timescales for this are immense, however. For example, a black hole of one solar mass would take 1064 years to evaporate, whereas the age of the Universe is only of order 1010 years.
This article is an answer to the question (asked by Catrin Phelps, Winchester) 'Could a black hole ever die?'
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