Hawking Radiation Explained

Electromagnetic radiation which, according to theory, should be emitted by a black hole. The radiation is due to the black hole capturing one of a particle-antiparticle pair created spontaneously near to the event horizon.

Back in 1974, Stephen Hawking proposed and predicted that there is a radiation emitted by black holes. In honour of the physicist Mr.Stephen hawking, this was known as The Hawking Radiation.

It started in 1973, when Hawking visited Moscow where he met soviet scientist  Yakov Zeldovich and Alexei Starobinsky who showed him that according to theory of quantum mechanics, Black holes should emit particles and radiation. In 1974, he then predicted the radiation.

Lets have a look how this radiation works ? Hawking said that as we know that nothing can escape black hole once it is past the Event horizon(Boundary of a black hole). Now let’s have a look on empty space, empty space is not really empty, it consist of virtual particles which come into existence and then annihilate each other again. When this happens right on the edge of the black hole(event horizon) one of the virtual particle will be withdrawn into the particle and the other will escape and become a real particle. So the black hole is losing energy by this radiation.

This phenomenon happens incredibly slowly at first and gets faster as the black hole becomes smaller and then in the last moments it radiates away with the energy f billions of nuclear bombs in a huge explosion. It also seems like black hole getting evaporated.

This is not yet confirmed because the black holes we know suck in huge amount of gases and mass, such that its radiation swamp this little effect. Hawking said that if the black hole has mass say M, then it will glow like a blackbody of temperature 6 x 10^-8/M kelvins . This tells us that it is significant for small black holes.

This process is incredibly slow, the total age of the black hole of M solar masses is 10^71 M^3 . This means that when the last black hole will get evaporated, no one would be around to witness it. The universe would have become uninhabitable long before then.

Black hole information paradox

Soon after the prediction of this theory, it was realised that this created an information loss problem.

According to Einstein’s general theory of relativity we know that all the information that crosses the boundary of the black hole (Event horizon) is lost forever not even light can escape its high pull. But as we explained it earlier according to hawking radiation virtual particle escapes taking some energy of the black hole as a radiation. “According to Hawking’s calculations, the lingering radiation – the only trace of a vanished black hole – contains no useful information about how the black hole formed and what it ate.”So when a black hole is evaporated, according to hawking information is lost forever which is a problem from the point of view of quantum mechanics, as it says that information can never be lost.

In 1973, John wheeler proposed the idea of “bald blackholes or no hair blackholes”. He said that black holes could only be distinguished by the externally visible parameters i.e by its mass, electric charge and angular momentum. And does not depend upon the type of information absorbed or lost in the black hole. For example if two black holes have identical visible parameters they are indistinguishable irrespective of the matter it is made of, it may happen that one is made up of matter and another is made up of antimatter. Hawking always remained against this ‘no hair theorem’ .

Possible Solution Proposed by Hawking

In January, this year Hawking published a paper online which is alleged to give a possible solution to the information loss paradox of hawking radiation. In this paper, Hawking said that when the particles are absorbed inside the black hole they leave behind the information associated to the particle in form of  two-dimensional holographic imprint on the event horizon. So when the particles which escapes the black hole during hawking radiation pick up the imprint from the event horizon and bring it back to the universe. But this solution is highly controversial and is already the centre of many discussions all over the world. Till scientists find the perfect solution to this , you sitback and keep reading at Scienceaholic.com .