Astronomy and Astrophysics
Hawking Radiation!!!
In today’s blog, I am going to explain an extraordinary theory by an extraordinary man on an extraordinary topic.
It all started
when a famous British physicist Stephen Hawking studied quantum mechanical
phenomenon near the event horizon of black hole in 1974. At that time, he came
up with an extraordinary theory that every black hole should constantly emit
electromagnetic radiation. Today, this theory is widely accepted and this
radiation is called as Hawking Radiation.
In my previous
article on virtual particles, I explained how virtual particles are created by
virtual fluctuations. If you haven’t read that article then I will recommend
that please read that article before reading this article to understand this
article in a better way.
How virtual
particles are responsible for Hawking Radiation???
Let us imagine
that a pair of virtual photons are created near the event horizon in such a way
that one of the virtual particle is created outside the event horizon and other
is created inside the event horizon. The virtual particle which is created
outside the event horizon narrowly escape the gravitational pull of the black
hole. But, the particle which is created inside the event horizon cannot escape
the gravitational pull of the black hole and get ‘lost’ forever.
Stephen Hawking |
Since these are
virtual particles they should be destroyed immediately and purely by
annihilation. But this cannot happen in this case because one virtual particle
is escaped and other one is lost for forever which means they cannot collide
for annihilation.
What will happen
with the escaped virtual photon???
The answer is
something seemingly impossible. It will become a classical photon and leaves
the surroundings of the black hole as Hawking radiation.
How virtual photon
get energy to convert into classical photon???
Since photon cannot
be created out of nothing due to the law of conservation of energy so, this
case create a disastrous problem in physics. One does not have to worry about
the law of conservation of energy as long as photons are virtual, since they
borrow energy of vacuum fluctuations to make these virtual photons.
But, here it is
not happening as the virtual particles are not going to collide. So, here Hawking
comes to rescue. According to his theory, the virtual photon gets energy to
convert into classical photon from black hole itself.
However, this has
a surprising consequences. As the black hole gives away it energy to the
virtual photons it emits to convert to classical photons, its own mass decreases
and black hole starts evaporating. The smaller the black hole faster it
evaporates.
That’s why as I explained
in my article on the end of universe that if our universe will end with big
freeze then at the last, black holes will get evaporated and that will be the
last phenomenon of our universe.
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Thanks for reading.....
See you next time!!!
-Ratnadeep Das Choudhury
Founder and Writer of The Dynamic Frequency
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