Would you like to  know
more
about
black holes?
So let's learn about
Hawking Radiation
In the past it was thought that black holes do not emit anything
however, Stephen Hawking pointed out that if quantum effects are taking into account
they can radiate thermal energy and particles
But what is a black hole? well, this is the definition
Just kidding...
Well, basically a black hole is a cosmic body where gravity is so strong
It is bounded by a define surface known as Event Horizon and where nothing can escape
Unless the body has an escape velocity equal or exceed the speed of light
the gravity is so strong because matter has been squeezed into a tiny space called singularity
So both density and gravity become infinity and the laws of physics break down there
So what's hawking radiation?
In 1974 Stephen Hawking proposed a shocking theory in the physics world,
by saying that black holes are not as black as they are painted after all
So if we take quantum effects into account black holes will thermally create and emit subatomic particles
until they evaporate completely by losing their energy
but how does it work?
To undestand this let's talk about a bit of quantum fluctuations
Which is basically the temporary appearance of energetic particles out of nothing
, as allowed by the uncertainty principle proposed by Heinsenberg
Also, as you should know according to quantum field theory, the quantum vacuum is not empty as in the
vacuum of the classical physics because it is filled with virtual particle pairs which constantly appear
for a short time and then annihilate each other.
So if we consider this near to the event horizon of a black hole
The annihilation of virtual particle pairs can be affected because of the strong gravitational field
Allowing for one to fall in and the other one to escape as Hawking radiation
For example, imaging  having an electron and a positron being about to annihilate each other
just outside of the event horizon
but because of the strong gravitational field the positron which has negative energy
and negative mass falls into the black hole and the other one  escape as thermal radiation
Hmm and what happens with the black hole?
Well this radiation carries energy away from the black hole and reduce its mass therefore a black hole shrinks until it evaporates
But this effect is important just for very tiny black holes because for Astrophysical black holes, which are very massive
they will need a time much longer than the age of the universe to evaporate
oh, and by the way
This was perhaps one of the first theories ever which combined, at least to some extent, quantum mechanics
and general relativity. So thanks for your legacy professor Hawking
