Реферат: What Is The Black Hole Essay Research
What Is The Black Hole Essay, Research Paper
What exactly IS a black
hole?
With all the excitement surrounding the new Star Wars movie, it is a
big day for lovers of science fiction. But how much does the average person
really understand about beaming up; phasers and photons; wormholes and
warp drive? How powerful are these fantasies compared to the real thing? If
theories of their existence are true, black holes are the most powerful force in
the known physical universe; however, do they even exist? Most scientists
believe so, but by their very nature, black holes are impossible to observe.
One can only see how the hole affects the space around it, and draw
conclusions from there. Enough information is known to imagine what it
would be like to explore one in a spaceship during a far distant Star Wars
future, though.
Many people are familiar with the term black hole, but few people
actually know anything about this phenomenon beyond reading science
fiction books. A black hole forms as a result of a massive star running out of
fuel to burn. Once the star is no longer exerting outward force by burning off
gases, it begins to collapse under its own intense, inward gravity (Chaisson
193). It is like slowly letting the air out of a balloon. Once the star is shrunk
to a certain size, while its mass, or weight, remains the same, its gravity
becomes so powerful that nothing can escape (Hawking 87). This critical size
to weight ratio is known as the Schwarzchild Radius (Hawking 87). Once a
black hole is created in this way, an invisible area, or boundary exists. If any
object crosses this line, it can no longer escape the gravitational force of the
black hole (Hawking 87). This line is called the event horizon (Hawking 87).
If black holes are proven to exist, beyond theoretical physics, then they would
probably be a very common anomaly in this universe. In 1915, Albert
Einstein put forth the first real proposition of such an anomaly in his Theory
of Relativity (Black Holes FAQ). In the 1930s, three physicists, doctors
Volkoff, Snyder and Oppenheimer, were able to prove the validity of black
holes mathematically. Since then, black holes have become a very important
and integral part of science and the over all understanding of the universe. It
has been proven, mathematically, that black holes have infinite gravity based,
escape velocities and an immense affect on light, time and even the very
fabric of space.
What exactly is an escape velocity? All bodies in space have gravity.
According to Einstein s Theory of Relativity, this is because bodies with a
large mass, or weight, actually warp space (Chaisson 77). For example, if a
two dimensional sheet of cloth, stretched and suspended at four corners,
represents space, and a bowling ball is placed in the center, the sheet will
warp downward. If a golf ball is then set at the edge of the sheet and allowed
to move freely it will be attracted toward the bowling ball, unless the golf ball
is traveling at a speed great enough to not be affected by the curve. This
critical speed is known as an escape velocity. This is the speed at which an
object must travel to escape a body s gravitational force (Chaisson 77). If a
body is compacted, such that its weight stays the same but its radius, or size,
becomes smaller, it s escape velocity increases in proportion (Chaisson 196).
The simple formula for this, in physics, states that a body s escape velocity is
equal to the square root of its mass, divided by its radius (Chaisson 77). Since
a black hole s size is always decreasing and it s weight is always the same,
the escape velocity is infinite (Chaisson 195). This means that nothing can
escape a black hole past the event horizon, not even light.
Light is made up of waves and particles. These particles strike an
object and bounce off. After they ve bounced off the object they move at a
different speed and direction. When the hit our eyes, or telescopes, or other
instruments, we interpret the speed and movement and see what they ve
bounced off. It was discovered, in 1676, by Danish astronomer, Ole
Christenson, that light travels at a very high, but finite speed (Hawking 18).
These properties of light govern that it must be subject to forces of nature,
such as gravity, and a black hole has more than enough gravity to spare.
Light travels at such a high speed that it is not affected by gravity, unless that
gravity is very strong. A black hole s gravity is powerful enough to trap light
because its escape velocity, being infinite, exceeds the speed of light
(Hawking 82). This is why a black hole is black. Once light crosses the event
horizon, it is drawn into the hole in space. Although the light is still hitting
objects, it is not able to bounce off to indicate their existence to an observer,
therefore the black hole appears as a void in space. Closing in on the edge of
the event horizon, light travels back to an observer at a slower and slower
rate, until it finally becomes invisible. This is due to heavy gravity and the
effect that a black hole has on time (Black Holes FAQ).
However, with a creative observation used in physics, it is possible to
indirectly observe a black hole. Scientists routinely measure an object s
gravitational pull by its affect on the objects around it. Picture this: You must
find a black cat in a coal mine. You can neither see the black cat nor the coal.
However, there is a spool of glow-in-the-dark yarn in the mine. You see a
string of the yarn twisting around and know that the cat is playing with it,
even though you cannot see the cat. Imagine the coal mine is space, the cat is
a black hole, the ball of yarn is a star, and the string attached to the ball is
matter being expelled by the star, known as the star s accertion disc (Black
Holes FAQ). In rare instances scientists will find a star near a black hole, a
binary star system where one of the stars has imploded into a black hole.
Physicists can observe matter being expelled from the star and being pulled
toward another object before the matter vanishes, or passes the event
horizon (Hetche).
According to Einstein s General Theory of Relativity, time is not a
constant (Hawking 87). Time is relative to an observer and his or her
environment (Hawking 87). It has been proven that time moves slower at
higher speeds (Hawking 87). In other words, time can be just as volatile as
light or dirt. An example of this aspect of time is a singularity; an event or
point that has a future or a past, but not both (Hawking 49). In human life,
death would be considered a singularity. A black hole is also considered a
singularity.
If an object crosses the event horizon of a black hole, it relatively
ceases to exist, because it has no future, since it can never escape. There is
the chance that time slows or stops the closer you get to the center of the
black hole (Hawking 88); since absolutely nothing in the known universe can
survive in or escape from a black hole. It can be said that time is stopped
within the event horizon. The only way for an object to escape this fate would
be for a strange anomaly to occur in the fabric of space, caused by a
theoretically different type of black hole than is generally excepted. If the
mathematics that describe this black hole are reversed, the outcome is an
object called a white hole (Black Holes FAQ).
As the complete opposite of a black hole, a white hole is an object into
which nothing can fall and objects are only spit out (Black Holes FAQ). At
this point, white holes are strictly theory. Their existence is highly unlikely. If
certain properties, such as motion or a positive or negative charge are applied
to a black hole, then the possibility of a white hole forming within the event
horizon arises (Black Holes FAQ). This leads to an even more improbable
occurrence called a wormhole (Black Holes FAQ). In theory, a wormhole
would be a tear in the fabric of space. Since time essentially has no effect on
a black or white hole, due to the event horizon, if an object were to fall into a
wormhole, it could be spit out anywhere in time or space (Black Holes FAQ).
How is it possible to test this theory if no signals can escape the black hole?
Simple, enter the black hole yourself.
Suppose one were the captain of a starship, three or four hundred years
in the future, and one approached a black hole. What would one see?
Nothing, no thing, which is what will tell you that the black hole is there. Due
to the hole s light absorbing properties, you wouldn t be able to detect any of
the stars behind it. Because no signals emanate from the black hole, you
wouldn t be able to tell anything more about it without passing through the
event horizon.
If you chose to penetrate the event horizon of the black hole nothing
would have seemed to change from your perspective. One could still receive
radio signals or other signals from outside the black hole, however, since no
signals or light from your ship can escape, it would appear to observers that
your ship had vanished. From here on, none of your discoveries could ever
be made public, because there would be no way to send your findings to the
outside world.
After this point, no scientist is sure of what would happen to you and
your ship. The most likely scenario would be that you are torn apart by the
immense gravity. Nevertheless, if one were to survive, what would someone
find at the center of the black hole? Better yet, could the ship ever reach the
center of the black hole? Probably not. As you ll recall, a black hole s center
is always getting smaller and smaller so you never really could reach the
center (Chaisson 195). Even if someone were brave enough to enter the event
horizon, it is likely that even he would never reach the singularity.
Perhaps black holes are the ultimate mystery of the universe. They are
impossible to observe, from within or without. Although black holes have not
been conclusively proven to exist, there is strong evidence that they do. Even
if they don t, black holes are very important to the worlds of astronomy and
physics and even literature. Scientists have vastly increased their knowledge
of the universe and the properties of matter through exercises that seek to
discover a black hole s effect on light, time and the very fabric of space.
Whether or not we ever really find them, black holes, white holes, and
wormholes will give science fiction writers ideas for many years to come.
Chaisson, Eric. Relatively Speaking: Relativity, Black Holes, and the Fate of
the Universe. New York: W.W. Norton & Company, 1988
Hawking, Stephen. A Brief History of Time: From the Big Bang to Black
Holes. New York: Bantam Books, 1988
Online. Internet. Black Holes; Frequently Asked Questions:
www.csvrgs.k12.va.us/Courses/IntroTech/pages/blackholes.html
Interview on IRC (Internet Relay Chat):
Hetche, Peter. Junior, University of Georgia