Black Holes

Black Holes 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.

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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 cant control your falling to the center as much as you cant 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.

Black Holes

If theories of their existence are true,
black holes are the most powerful force in the
known physical universe. Many people are familiar
with the term black hole, but few people actually
know anything about them. A black hole forms as
a result of a massive star running out of fuel to
burn (Chaisson, 193). 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 compacted to
a certain size, while its mass, or weight, remains
the same, its gravity becomes so powerful that
nothing can escape it (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 line
around it 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 (Bunn, 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
effect on light, time and even the very fabric of
space. All bodies in space have gravity. According
to Einsteins 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 effected 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 bodys
gravitational force (Chaisson, 77). If a body is
compacted, such that its weight stays the same
but its radius, or size, becomes smaller, its
escape velocity increases in parallel (Chaisson,
196). The simple formula for this, in physics, states
that a bodys escape velocity is equal to the
square root of its mass, divided by its radius
(Chaisson, 77). For example, if a bodys mass is
two-hundred, and its size is twelve and one half,
the escape velocity would be four. If the size of
the same body is reduced to two, while its mass
remained at two-hundred, the escape velocity
increases to ten. Since a black holes size is
always decreasing and its 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. 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. Light travels at such a high
speed that it is not observably effected by gravity,
unless that gravity is very strong. A black holes
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, therefor 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
(Bunn, Black Holes FAQ). According to
Einsteins General Theory of Relativity, time is
not a constant (Hawking, 86). Time is relative to
an observer and his or her environment (Hawking,
86). It has been proven that time moves slower at
higher speeds (Hawking,

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Black Holes

Black Holes
Every day we look into the night sky, wondering and dreaming what lies beyond our galaxy. Within our galaxy alone, there are millions upon millions of stars. This may be why it interest us to learn about all that we cannot see. Humans have known the existence of stars since they have had eyes, and see them as white glowing specks in the sky. The mystery lies beyond the white glowing specks we see but, in the things we cannot see in the night sky such as black holes.

Before I begin to speak about black holes, I will have to explain what the white glowing specks in the sky are. Without a star a black hole could not be formed. In the beginning of a star life a hydrogen is a major part of its development. Stars form from the condensation of clouds of gas that contain hydrogen. Then atoms of the cloud are pulled together by gravity. The energy produced from the cloud is so great when it first collides, that a nuclear reaction occurs. The gasses within the star starts to burn continuously. The hydrogen gas is usually the first type of gas consumed in a star and then other gas elements such as carbon, oxygen, and helium are consumed. This chain reaction of explosions fuels the star for millions or billions of years depending on the amount of gases there are.
Stars are born and reborn from an explosion of a previous star. The particles and helium are brought together the same way the last star was born. Throughout the life of a star, it manages to avoid collapsing. The gravitational pull from the core of the star has to equal the gravitational pull of the gasses, which form a type of orbit. When this equality is broken, the star can go into several different stages. Some stars that are at least thirty times larger than our sun can form black holes and other kinds of stars.
Stars explode at the end of their lifetime, sometimes when they explode the stars leave a remnant of gasses and, dust behind. What the gasses come together to form depend on the size of the remnant. If the remnant is less than 1.4 solar masses it will become a white dwarf, a hot dead star that is not bright enough to shine. If the remnant is roughly 1.4 solar masses, it will collapse. “The protons and electrons will be squashed together, and their elementary particles will recombine to form neutrons”. What results from this reaction is called a neutron star. The neutrons in the neutron star are very close together, so close the pressure prevents the neutron star to collapse onto itself. If the remnant of this giant exploding star is larger than three solar masses or ten times our sun, it becomes a black hole. A black hole is one of the last option that a star may take.
In the 18th century scientists started to research the after effects of a large star such as a supernova exploding. What happens of the gas and dust left behind after such a big star died? The idea of mass concentration so dense that even light would be trapped goes all the way back to Laplace in the 18th century. The first scientist to really take an in depth look at black holes and the collapsing of stars, was a professor, Robert Oppenheimer and his student Hartland Snyder, in the early nineteen hundreds. They came up with the basics of a black hole from Einstein’s theory of relativity that if the speed of light was the most speed over any massive object, then nothing could escape a black hole once in its grasp. These researchers showed that when a “sufficiently massive star” runs out of fuel, it is unable to support itself against its own gravitational pull, and it should collapse into a black hole. In general theory of relativity, gravity is a manifest of the curvature of the space-time.
“Einstein general theory of relativity showed that light, though it does not react to gravity in the same way as ordinary matter, is nevertheless affected by strong gravitational fields. In fact, light itself cannot escape from inside this region”.(Internet Public Television family science show)
Massive objects distort space and time, so that the usual rules of geometry don’t apply anymore. Near a black hole, this distortion space is extremely severe and causes black holes to have some very strange properties.

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A black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. Afer a black hole is created, the gravitational force continues to pull in space debris and other type of dust to help add to the mass of the core, making the hole stronger and more powerful. Most black holes are spinning; The spinning of the black hole allows more debris to become a part of its ring which is called the Event horizon. The debris spins within the ring until it becomes a part of the center of the black hole adding to the mass of the core, making the hole stronger and more powerful. The event horizon is also known as the boundary. The event horizon is the point where the black hole’s gravitational pull begins. Once you cross the event horizon, there is no turning back. The way that someone can escape a black hole’s event horizon once it has entered, is by exceeding the escape velocity. The escape velocity means moving faster than the speed of light. Since moving faster than the speed of light is impossible, so is escaping a black hole’s gravitational pull. So in order for the black hole to swallow something up, that thing will have to pass the event horizon. If someone were to fall into the event horizon, they will begin spinning around the center of the black hole at the speed of light. As the person gets closer to the center, the “singularity” effect takes place. This theory means that once you are in the event horizon the gravitational pull at the center of the black hole is greater at your feet than your head. This singularity effect will stretch the person out to infinite thinness until you are torn apart, thus killing you. The time it takes a person to die depends on the size of the black hole. A smaller black hole means that its “singularity” is not far away from the core thus killing you faster. A larger black hole will allow you to stretch slower giving you time to look around the inside of a black hole. If one were able to look around in the event horizon images would be distorted. And since light can go into a black hole, you can see outside images fine. But light won’t be able to bounce of you and go back, so no one would be able to see you. Even though it is impossible for someone to experience this, scientists speculate that this is what would happen. Basically you would be in a place where time does not exist and all of Einstein’s laws will fail.

Even though we cannot see black holes scientist know they are really exist. Scientists have not actually discovered black holes’ but, there are some speculations as to what they think black holes are. If there is a large quantity of mass in a small area, there is a good chance it is a black hole. A black hole emits radiation, and the energy to emit this radiation comes from the black hole’s mass similarly, to a star.

Scientists are aware of this radiation field so, they use technological advancements for measuring such things like radiation. The core of the black hole appears to be purely black on all readings even through the uses of radiation detection devices. Another idea scientists use to speculate black holes’ exist stance, is by observing other stars. Stars in the sky revolve around other stars and sometimes planets. Just like our planets revolve around our sun. Our sons’ gravitational force keeps our planets in their revolutions. Now imagine our son was a black hole. The black hole has the same characteristics of a star but you just can’t see it. So when scientists see a star revolving but, cannot see what is causing its evolution; This may be another sign that the star may be revolving around a black hole.

Just recently a major discovery was found with the help of a device known as The Hubble Telescope. This telescope has just recently found what many astronomers believe to be a black hole, After being focuses on a star orbiting empty space. Several pictures of various radiation fluctuations and other diverse types of readings that could be read from that area which the black hole is suspected to be in.
Bibliography1, Jastow, Robert. Red Giants and White Dwarfs. Canada: George J. Mcleod,1990.

2, Alter Dinsmore, Cleminshaw H. Clarence, Philips G John. Pictorial Astronomy. United States: Sidney Feinberg, 1963.

3, Folger, T. In the black.1993,Jan
4, Internet, Black holes, Newton’s Apple, Public Televisions Family Science Show.
5, Internet, search black holes at ask.com

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