Black Hole is a curious term to all the science enthusiast.This term was coined by American scientist John Wheeler in 1969.I have compiled the explained by the great scientist Stephen Hawaking in his book.A brief history of time and information provided on the official website of NASA. The nature of light makes it more interesting to understand about the black hole.Light can be regarded both as wave and a particle.It is not clear how light responds to gravity if it is treated as a wave only.But if light is made up of particle one might expect it to be affected by gravity.Light travel with infinitely speed.Stars that are massive field that light would not escape.Any light emitted from the surface of star would be dragged back by the star gravitational attraction.It is suggested that there are a large numbers of of stars like this in our universe.They are often termed as blackhole. A star is formed when a largeamount of gas (mostly hydrogen) starts to collapse itself due to gravitational attraction.As it contracts the atoms of gas collides with each other,more frequently at greater speeds and the gas heats up.The gas atoms will be so hot that the hydrogen atoms eventually coalesce to form Helium.The heat released in this reaction is like a controlled hydrogen bomb explosion.After billions of year the fuel of star finishes and the fate of star depend on the mass of it;before it runs out of fule.The very massive star ends up forming a blackhole. Many stars must have burned all their nuclear fuel and have had to collapse.It is evident that there is a much larger blackhole ,with a mass of about a hundred thousand times that of the sun ,at the center of our earth galaxy"Milky way".Stars in the galaxy that come too near this blackhole will be tron apart by the difference in complex study of physic that depends on the great theories of this century,general relatively and quantum mechanics. The most common type of medium sized blank hole is called stellar.The mass of stellar blackhole can be up to 20 times greater than the mass of the sun and can fit inside a ball with a diameter of above 10 miles.It means that the blankhole is a very compact mass. A blackhole cannot be seen because of the strong gravity that is pulling all of the light into the blackhole center.The serching of blackhole is like a searching black cat ina cola mine.But the effect of blackhole can be observed by the help of stars and gasses around it.Blackhole do not wander randomly swallowing the heavenly bodies.The orbit of blackehole would have to be very close to the solar system to affect our earth which is not likely. The sun does not have enough mass to collapse into blackhole.In billion of years,when sun will be at the end of its life,it will become a red gaint star finally forming a white dwarf star.