Question: whats a black hole

Paul Higgins answered on 14 Nov 2012:

When stars explode, we call them a “supernovae”. For the most massive stars, their supernovae form “black holes”, which are so dense that at their centers, we can not describe how strong gravity is… (mathematically it is infinite!) And their “surfaces” are described by the place where if a light beam comes too close, it will be “sucked” into the black hole. Light travels ~300,000,000 meters per second, so for something going that fast to be trapped by gravity, is pretty amazing.
There are other types of black holes, like the one at the center of our galaxy that is ~6,000,000 times as massive as the Sun- it is a mystery how it formed. Also, it is possible that tiny black holes form every day at CERN, the particle collider. These black holes would be so small and only last for a fraction of an instant, that they just disappear, without sucking anything into them. So far the Earth has not been devoured by them, so I think we are OK.