Black Holes Essay, Research Paper

Black Holes

Black holes are one of the more bizarre and intriguing predictions of Einstein’s

theory of gravity. Surprisingly, there is now a great deal of observational evidence that

black holes do exist, both in binary star systems and at the center of most galaxies,

including our own. Although we are gaining more knowledge of black holes, they still

remain one of the strangest things anyone has ever heard of, and we may never know what

exactly one of these things are and can do.

It is impossible to manufacture black holes in a laboratory. The density of

matter required is too great. In order to make a black hole the size of a baseball, you

would have to pack all the matter in and on the Earth into a volume the size of a fist.

Nature can make black holes, however. Matter naturally collapses unless there is some

other force to hold it up. The objects in a room are kept from collapsing by

electromagnetic forces. The gas in an active star is held up by thermal pressure. However,

once a star uses up its thermonuclear fuel, it starts to collapse, and if there is enough mass

to overcome other, microscopic forces, it collapses into a black hole. According to

Einstein’s theory, if we could pack enough matter into a small enough volume, the thing

created inside will get so deep that the matter inside can never escape. A circle of no

return forms. Any matter that passes the point of no return can no longer escape to the

outside world. It necessarily keeps collapsing, moving towards the center. It gets deeper

and deeper until finally a hole is literally torn in the fabric of spacetime:

the density of matter at the center becomes essentially infinite. Thus, what is meant by “a

hole in the fabric of spacetime” is: a tiny region of space where the known laws of physics

break down. A black hole is a region of space so tightly packed with matter, that nothing,

not even light can escape. Hidden at its center is a tear in the fabric of spacetime. Stephen

Hawking showed in the mid-seventies that black holes aren’t actually black. They glow in

the dark. They emit radiation via microscopic processes that occur just outside the

horizon. This means black holes ultimately evaporate. In reality, though, a solar mass

black hole will take many times the lifetime of the Universe to evaporate.

In some sense, a black hole marks a boundary to spacetime: a horizon beyond

which no one can see without travelling through it. This radius of no return is called the

event horizon of the black hole. All the bumps and wriggles of the matter from which they

were formed are smoothed out as the matter contracts, so that the final shape of the

horizon is always perfectly smooth and round. This is where everything gets really weird.

To a distant observer, events near the horizon appear to slow down. If you drop a clock

into a black hole it appears to tick more and more slowly as it approaches the event

horizon. Time actually appears to stop right at the horizon. The clock’s motion towards

the black hole also slows down and to a distant observer it takes literally forever to fall

through. If you fell in the event horizon with the clock, you would be sucked into the

singularity in no time. As you fall, time and space become jumbled, and you can?t control

your falling to the center as much as you can?t help yourself falling into the future.

Black holes are definitely one of the most bizarre things anyone has ever heard of.

We will never totally understand everything about them. They make up only a small part

of our mysterious universe, though.