6.When gravity operates over microscopic distances—for instance, at the center of a black hole, where a hugemass is packed into a subatomic volume—the bizarre quantum properties of matter come into play, and string theory describes how the law of gravity changes.
10.The current picture is that all galaxies may have a supermassive black hole in their center, and that this black hole swallows gas and dust in the middle of the galaxies generating huge amounts of radiation - until all the nearby mass has been swallowed and the process shuts off.
