black holes

When the star got shrunk to a certain critical  radius,the  gravitational field at the surface becomes so strong that the light cones are bent inward so much that light can no longer escape.
Acc to the theory of relativity nothing can travel faster than light.thus if light cannot escape,neither can anything else,the gravitational field is so strong that nothing can pass through it ;so everything got dragged by the gravitational field.This region through which even light cant escape is now what we call a black hole.time has also a different meaning across a black hole.
If you were watching a star collapse to form a black hole,one has to remember that in the theory of relativity there is no absolute time each observer has its own measure of time.The time for someone on a star will be different from that for someone at a distance,,because of the gravitational field of the star.

• Because of the high gravitational field across the star even time is slow across it. 

• So all we know about the black holes is just a introduction we have to discover a lot about these amazing creatures and who would know that our universe is also a part of a massive Black Hole.