Among other things, general relativity theory of Albert Einstein predicted the existence of one of the strangest cosmic phenomena - black holes. Recent hypothesis suggests that our galaxy is in the midst of a massive black hole. Why are these holes "black"?It is known that mass distorts space. We also know that the path of light is affected by gravity. We also know that Einstein's theory of general relativity predicts the existence of one of the strangest objects imagined by physicists - black holes.