Black Hole There are many stars approaching their death. But very few stars they will become black hole to the point they will become invisible. Black Hole Now we can understand this by a concept- "If I have a stone so I can throw it upwards, it will go little bit up and it comes down. And I again throw it little hard it further go up and comes down. But if I throw stone so fast that it will manage to escape from the earth's gravity that have speed something like 25000 miles I don't quit remember but some escape velocity . Now that escape velocity that speed through which you should have to throw it is much larger like say that for the sun and much larger that for the moon." Black Hole Now if imagine you would take light or straight beam i.e. flash light and we know that gravity act on light. By Eienstein equation light is affected by gravity. Now if the gravity is so strong light it goes up and comes down in another word light does not escape...