Expert: Tom Whiting - 4/21/2009

Question
Hi, i have a few questions about black holes. I have always wondered what happens to things when they get sucked into a black hole. Also, how exactly do they form from an exploding star? What happens in the center of the black hole to keep it going for a longer time? Any help would be great. Thanks.

Answer
Hi Mark,
A black hole can form from the compressed core of a very massive
star as it goes supernova...the tremendous pressure from the implosion. (That's correct, a supernova is an implosion, not an explosion....as the outer layers of the massive star come crashing down onto the core, and rebound).  This compresses the core to first the neutron star stage where electrons are forced to merge with protons to form a big ball of neutrons about 10-20 miles in diameter.
However, if the supernova is even more forceful, it can over-ride
even neutron pressure - that force that prevents neutrons from
gathering just so close, and this crushes the matter down to what
we call a singularity....a pin point, and thus forms a black hole.

Black holes do not suck...gravity does not suck.  Gravity, as shown
by Einstein's general relativity (Circa 1917) is simply a curvature
of space due to the presence of a mass. With a black hole, the
space (or more correctly, the space-time continuum)  is completely wrapped spherically around the massive body at the center.  So anything venturing in too close to the "event horizon"...the invisible outer limit of a black hole where the escape velocity exceeds lightspeed, has to follow the curvature of space and spirals right down into the black hole. That's how it works.
There is no "sucking" in the normal sense, with gravity. Even
the Earth does not "suck" you in, it simply curves space slightly, around the Earth.  (Review Einstein's General Relativity).

This is why in a crowded region around a black hole, the
matter doesn't go directly into the black hole, but goes into a
highspeed orbit around the black hole, just outside of the event horizon.  This matter gets heated extremely hot, and gives off X-rays and Gamma ray radiation...we call this an accretion disk, and that's what IS visible surrounding the black hole, and how we can
study them, whereas the black hole itself is invisible to us, as even light cannot escape from regions inside the event horizon.

We really don't know (and perhaps can never find out as even light,
radio waves, etc. cannot escape from inside the event horizon) what goes on inside the event horizon, and at the center of a black hole. We can only assume that all matter at the center (assuming it IS at the center) is a pin-point, called a singularity, but we really
don't know, and may not ever be able to find out, no matter how
technologically advanced we become.  Even science cannot know the
unknown, as Mr. Spock of Startrek once said..... OR, as Einstein once said, "God not only throws the 'dice'....sometimes He hides the dice".  
So we don't really know what happens to matter once it goes past the event horizon...give the laws of gravitational tidal forces, eventually a falling astronaut falling into a black hole would be stretched infinitely (as the force on his feet is much
greater than his head eventually)...in any case, most believe this tidal force stretching... would be fatal, to anything and everything,
even a spacecraft entering the event horizon would be destroyed
by super-strong tidal forces..... Read that...tighter and tighter curvature of space being encountered as it goes down into the black hole region.  
Clear Skies,
Tom Whiting
Erie, PA  USA