Black holes are said to
have a gravitational field and the area where the gravitational
field ends is called the event horizon. Light can enter the event
horizon but cannot escape it. It is this area – the event horizon –
that separates the all-consuming black hole from the rest of the
universe. Anything that crosses the event horizon goes into the
black hole forever. Whatever goes in collapses into an infinitely
dense point. This point is referred to as singularity. It is
reasoned out by scientists that whatever gets past the event horizon
is pulled into the black hole at a speed of 186,000 miles per
second. It is frightening enough to think of the existence of one
One theory says that
there is a massive black hole at the centre of every galaxy and that
it is this that holds all the different solar systems together.
Scientists have, in fact, discovered several types of black holes.
These scientists have had their names immortalized by the naming the
black holes after them. Examples of these are Schwarzchild,
Reissner-Nordström, Kerr, and Kerr-Newman black holes. They are all
not similar. Schwarzchild black holes do not rotate and have no
charge, whereas Reissner-Nordström black holes do not rotate but
have a charge; Kerr black holes rotate but have no charge, and
Kerr-Newman black holes rotate with a charge!
A black hole cannot be
seen. How then do we know it exists? Scientists have found a lot of
indirect evidence that points decisively at the existence of black
holes. In 1994, the Hubble Space Telescope was used to uncover the
first convincing evidence that pointed at the existence of a black
hole. Evidence of the presence of a huge body that could not be seen
was found at the centre of the galaxy.
Analytical abilities of
the best of scientific minds are aimed at finding out any possible
ways that black holes can be useful to man. Maybe it could be used
as a disposal centre for nuclear by-products. However, for this, man
would first need to devise methods to go near and throw the wastes
and return! A tall order indeed. But then man has achieved many
times over what has been believed to be impossible. So he might even
turn black holes to the advantage of the human race.