Black Holes

1.

Definition: region of space so densely packed with matter that nothing, not even light, can escape (i.e. escape velocity greater than speed of light)

2.

Black holes form by gravitational collapse of stars that have burned up all thermonuclear fuel or by collapse of stars at center of galaxy.

3.

surface that separated the region of no return from the rest of the universe is called the event horizon of the black hole

4.

Black holes that weigh one solar mass have a radius of about 5 km.

5.

At the center of a black hole is a singularity, where all the mass of the black hole is concentrated and the known laws of physics break down.

6.

Inside the event horizon time and space exchange roles; once you fall below the event horizon you can no more avoid falling to the singularity at the center than you can avoid moving from 2:00 o'clock to 3:00 o'clock when you are outside.