Friday, July 29, 2011

What are black holes?

Well, we sometimes hear about black holes. Black holes are a very important branch of physical sciences. The secrets of the universe is somehow related to blackholes.
We wonder what are they. A black hole is a place/region in outer space, where nothing can escape. No particles can escape from black holes, if they fall inside once, even light. Around a black hole there is place called event horizon ; once any particle is beyond this position, it cannot return.
Once a blackhole is formed, it grows continuously forever. It does so by absorbing mass from the surroundings. It gains mass from nearby planetary bodies and then continues to grow.
The idea of black hole was put forward by the scientist John Michell. He stated this in a letter to another scientist named Henry Cavendish, who is famous for his discovery of hydrogen.

A black hole

Here a question arises : Does gravity influence light's motion?

Einsteen answered the solution to this question. He proved that gravity influences light's motion. He developed his theory of general relativity in 1915.

Physical properties of Black holes
  • They have mass.
  • They do not have angular momentum.
  • They do not have charge.
Hawking radiation

Hawking applied quantum theory in a static black hole background. As a result of this application, he was able to show us black holes are not entirely black, and also that they emit small amounts of radiations.