Until the end of the universe, black holes will be the longest living objects, but eventually
every black hole will die.
So today, we’re going to be discussing black holes and explaining Hawking radiation.
We might as well begin with the parts of a black hole.
At the very heart of all black holes lies the singularity: a point where matter collapses
to infinite density, spacetime has infinite curvature and the gravitational field strength
is infinitely strong.
The outer layer of a black hole is called the event horizon: the imaginary boundary
of a black hole where the gravitational field strength becomes so strong that nothing can
escape, not even light the fastest thing in the universe.
You can think of the event horizon as a river, which ends in a gigantic waterfall.
Further down the river and closer to the waterfall you go, the stream becomes faster and faster.
Once you’re past the point of no return, or in this case the waterfall, there’s no
going back.
No matter how fast you swim you can’t escape the pull of the waterfall.
Nothing can escape the pull of a black hole, if you get too close.
Unfortunately, we will never find out what goes on inside black holes, past the event
horizon, however, we do have some ideas of what occurs at the very edges.
Black holes evaporate their mass away.
All around us, virtual particles are constantly popping into existence.
They come in pairs, a particle and an antiparticle.
After existing for an extremely short amount of time, the two particles recombine and annihilate
each other.
If one of these particle pairs pops into existence at the event horizon, one particle will fall
into the black hole but the other is able to escape elsewhere.
And when particles escape, the black hole loses an extremely tiny amount of its mass.
This is called Hawking radiation, a process that's exceptionally slow.
Without a doubt, black holes will be the longest living objects for the rest of the universe,
because of how slow they deteriorate.
However, if the black hole is consuming enough matter, it can combat Hawking radiation so
that nothing happens or the black hole could be consuming enough matter that it actually
gains mass.
In these circumstances, black holes are eternal, assuming that they are always eating a constant
flow of matter.
It’s easy for more massive black holes to combat Hawking radiation but for smaller black
holes, it’s not as easy.
Black holes emit Hawking radiation at a rate inversely proportional to their mass.
So a small black hole evaporates very rapidly and has an associated temperature that is
very high, whereas a massive black hole evaporates much slower and has an associated temperature
that is very low.
Black holes at just the right mass, that formed near the start of the universe, will be coming
to the end of their lives right now.
What happens when a black hole comes to the end of its life?
We’re not entirely sure.
The best guess at the moment, is that the black hole radiates out for the last time
and evaporates into nothing.
As mentioned, the smaller the black hole, the quicker the process is.
So a black hole at the end of its life would emit Hawking radiation faster than its ever
done before and evaporate into nothingness.
However, this is a problem because as the black hole dies, the information it has gathered
over its lifetime also seems to die.
Information is what distinguishes one thing from another; what makes one particle unique
from another.
It’s the mass, spin, position, temperature and so on of any one particle.
According to the theory of quantum mechanics information cannot be destroyed; it can be
changed but not destroyed.
This has created a paradox, because black holes destroy information.
There are a few outcomes to the black hole information paradox.
First, the information is hiding, in whatever form it takes.
Perhaps black holes don’t disappear after all and a small part of it remains.
Maybe the information is emitted before or as the black hole evaporates into nothingness.
The information could separate into another black hole, that we cannot access but it would
mean that the information is not lost and our current laws of physics are not broken.
Second, we accept that information is lost.
The information would simply be irretrievable and gone forever.
We would need to remove some current laws of physics and rethink them.
And third, information is not lost.
When you put more material into a black hole, the black hole becomes larger, to make room
for the new information.
When two black holes merge, the remaining black hole has a combined mass of about the
sum of the two previous black holes.
More information translates into more surface area.
The black hole could be storing the information and release it on a later date.
Perhaps the information is conserved in parallel universes.
One idea is that the information is converted onto the surface of the black hole.
This is called the holographic principle.
If this is the case, and information is preserved onto the edge of a black hole, then it’s
very possible that Hawking radiation could read this information and take it away as
it’s emitted.
If all falling material has its information preserved onto the event horizon, it’s a
bit like the information is going from three-dimensions and then being stored onto a two-dimensional
surface; or in other words, a hologram.
Comment down below your thoughts on Hawking radiation.
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