Some Knowledge

In certain stars, the high mass and lack of thermonuclear fuel lead to collapse.  As the thermal energy that supports the star is radiated away, gravity compresses the gas to higher and higher densities.  If the mass of the star is 1.5 to 3.0 times the mass of the sun, there is supposedly no atomic force that can resist the crush of gravity.  With or without a massive supernova explosion, the spent star will collapse into a black hole.

The radius of a black hole is defined by the event horizon.  The event horizon is the distance at which the general theory of relativity predicts that time will stop because of the intense gravitational field.  Black holes are in many ways artifacts of Einstein’s general theory of relativity.  Because light interacts with gravity, it is possible that there can be such an intense gravitational field that light will not be able to escape.

It is theorized that the entire mass of the collapsed star will shrink down to a point smaller than a sub-atomic particle.  This is the so-called singularity, where gravitational force and density all approach infinite quantities.  Nevermind that the singularity lies inside the event horizon, where time has supposedly stopped.  The singularity exists at some infinite time in the future.

Black holes are thought to accrete matter from the surrounding universe.  This can happen by the object drawing in gas and dust from the surrounding regions of space, or by the black hole coming close to a star and drawing gas from the star into it’s gravitational field.  Any matter or energy that falls into the black hole will become a part of the black hole.  Any information such as mass, momentum, or temperature possessed by the accreting matter will be lost to the known universe.

Black holes suck up all the matter that has an orbit that intercepts their photon sphere.  The photon sphere is a region around the black hole in which a photon’s path would be bent into an orbit around the black hole.  The photon sphere is typically 1.5 times the event horizon.  In theory, there is nothing to stop a black hole from growing to completely engulf the universe.  Contrary to popular belief, a black hole does not hoover up material from space.  Any object that can go into orbit around a black hole will stay in orbit.  As long as nothing causes the orbit to decay, the object will not be sucked into the black hole.

Many physicists have spent considerable time working up the mathematical theory of black holes.  There is some observational evidence for these objects actually existing in space, and at the center of galaxies.  Despite what you might read in science fiction, there is no way to survive falling into a black hole.  The only universe you will emerge into if you try to travel through a black hole is the land of the dead.

For a longer and more detailed essay on black holes, check out this Wikipedia article.