Expert: James Gort - 8/27/2006

Question
Hi James,
I have many questions about Astronomy but I will ask some few only:
1) What is the end of a black hole and if it has a end, what u will find on surface ?
2)I saw 1 website about Big crunch, do u beleave it ?
3)I would like to know in an easy way what is the Relativity of Einstein

Answer
1)  If you're asking whether a black hole will have an end and eventually die, the answer is "maybe".  A black hole is not quite "black", but can emit particles at its boundary (termed the Schwarzschild radius).  So if a small black hole didn't grow bigger (more massive) by absorbing new material into it, it would just slowly radiate (emit those particles) and eventually (probably after billions of years!) cease to be a black hole any longer.  You could then see a very dense object instead of a black hole.  That object would probably be similar to a neutron star.

You also asked what you'd find on its surface.  A black hole doesn't really have a surface - it is a small point of very dense matter.  So you can't walk on a black hole - every atom in your body would be pulled to the point by gravity, and you'd become part of the point in the center.  You would have no more body!  

But a black hole does have a certain radius or size, which is the distance from the center which light can escape.  So if you looked at a black hole, it would appear to be a dark sphere.  You could not walk on the "surface" of this black sphere - there's really no surface - only a very bent space, with a very strong gravity pulling toward the center.  At the surface, you could not escape being dragged into the center of the black hole.  According to Einstein, the "space-time" is so warped that it would require an infinite amount of energy to not get dragged in.

2)  The Big Crunch says the Universe will eventually slow down and start contracting, so all matter, including us and everything we see, will condense into one giant black hole.  No, I do not believe that, since the latest evidence is that the Universe expansion is not slowing down, but is speeding up.

3)  There are actually two theories.  Einstein published the Special Theory of Relativity in 1905.  That theory states that all uniform motion is relative, and that there is no absolute state of rest.  All motion depends on the observer.    That theory also states that the speed of light (termed 'c') is constant.  The results of the theory are hard to observe unless you're moving very fast.  For instance, suppose you're on a train going at 50 miles per hour and you throw a baseball at 50 miles per hour to a friend in the train car.  If someone watching the train go by sees this, they could measure the actual speed of the baseball, and it wouldn't be 100 miles per hour.  It would be a little less!  If the train was moving at 'c' and if you could throw the baseball at 'c', the person on the ground would measure the speed at (not 2 times 'c'), but only 'c'!  So 'c' is the maximum speed anything can travel at.

The Special Theory also said that mass and energy are the same thing, only a different form.  This resulted in atomic energy and the atomic bomb.

In 1915, Einstein developed the General Theory of Relativity, sometimes called the Theory of Gravity.  He showed that gravity is not caused by an invisible force, but by the fact that every mass actually curves space and time.  Even light bends around a massive object.  And that's the reason light can't escape from a black hole.

Prof. James Gort