Wednesday, 14 March 2018

What is Hawking radiation?


One of the important contributions of Dr. Stephen Hawking is known after his name as "Hawking radiation". Before the invention of Hawking radiation it was thought that "black holes "can only grow larger in size by devouring nearby matter and cannot get smaller by losing matter, because the gravitational field of a black hole is so intense, nothing including light cannot escape from it.

Hawking showed that black holes can lose matter by a process called Hawking radiation. Black holes are usually born as the end product of a massive star that has reached the end of its life by exhausting all the nuclear fuel.

Super massive black holes having mass as great as million suns, are also known to exist at the center of galaxies. The existence of black holes was predicted by Einstein's General Theory of Relativity.

To predict this radiation he made use of two important but widely differing theories in physics like General Theory of Relativity and Quantum Mechanics. Theory of relativity shows that black holes have a spherical boundary in space called event horizon.

Any object crossing this event horizon from outside cannot comeback, the object will be absorbed by strong gravity and it will become a part of the black hole. According to quantum theory, empty space or vacuum is not actually empty.

Pairs of fundamental particles are constantly and spontaneously created and annihilated in empty space. In this pair one is matter particle and other is antimatter particle. In quantum physics this process of virtual particle production is called a quantum fluctuation or vacuum state fluctuation.

Hawking argued that if particle pairs are produced near the event horizon of a black hole then the pair can separate without self-annihilation. While one particle is absorbed by the black hole the other can fly away. This particle separation is at the expense of the black hole's gravitational energy, so the black hole loses some energy or its equivalent mass.

Thus tiny black holes may ultimately evaporate by this mass loss process.
-Godfrey Louis

Godfrey Louis is a professor at my University (Cusat), I copied this explanation from his facebook timeline.

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