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Q&A: Black Holes
Q:
What ultimately happens to black holes? Are they forever, or do
they eventually transition into some other state of energy
and/or matter?
A:
According to our current knowledge, black holes will eventually
evaporate by a process called Hawking radiation (after Stephen
Hawking). Eventually in this case means 10 to the 65th power
years (1 followed by 65 zeroes) for a 10 solar mass black hole,
and 10 to the 80th power years for a million solar mass black
holes (the evaporation time goes as the cube of the mass). For
comparison, the age of the universe is "only" about 15 billion
years.
Hawking radiation occurs because empty space, or the vacuum, is
not really empty. It is actually a sea of virtual particles of
every type that pop into and out of existence for a very brief
time. This is possible because according to the uncertainty
principle of quantum mechanics, energy may always be borrowed
from the vacuum, but it must be repaid quickly. The greater the
amount borrowed, the quicker it must be repaid. For example, the
energy to make an electron and its anti-particle, a positron --
virtual particles must be created in pairs must be repaid in one
sextillionth of a second or to use the scientific term, one
zeptosecond! Hawking showed that if a pair of virtual particles
is created near a black hole, there is a chance that one of them
will be sucked into the black hole before it is destroyed. In
this event, its partner will escape into space, and a virtual
particle will have become real. The energy for this came from
the black hole, so the black hole slowly loses energy by this
process.