Black Holes
General aspect of searching black holes and understanding of the
subject.
For
ages people have been
determined to explicate on everything. Our search for
explanation rests only
when there is a lack of questions. Our skies hold
infinite quandaries, so the
quest for answers will, as a result, also be
infinite. Since its inception,
Astronomy as a science speculated heavily upon
discovery, and only came to
concrete conclusions later with closer inspection.
Aspects of the skies
which at one time seemed like reasonable explanations are
now laughed at as
egotistical ventures. Time has shown that as better
instrumentation was
developed, more accurate understanding was attained. Now it
seems, as we
advance on scientific frontiers, the new quest of the heavens is to
find and
explain the phenomenom known as a black hole. The goal of this paper is
to
explain how the concept of a black hole came about, and give some insight
on
how black holes are formed and might be tracked down in our more
technologically
advanced future. Gaining an understanding of a black hole
allows for a greater
understanding of the concept of spacetime and maybe give
us a grasp of both
science fiction and science fact. Hopefully, all the
clarification will come by
the close of this essay. A black hole is probably
one of the most misunderstood
ideas among people outside of the astronomical
and physical communities. Before
an understanding of how it is formed can
take place, a bit of an introduction to
stars is necessary. This will shed
light (no pun intended) on the black hole
philosophy. A star is an enormous
fire ball, fueled by a nuclear reaction at its
core which produces massive
amounts of heat and pressure. It is formed when two
or more enormous gaseous
clouds come together which forms the core, and as an
aftereffect the
conversion, due to that impact, of huge amounts of energy from
the two
clouds. The clouds come together with a great enough force, that a
nuclear
reaction ensues. This type of energy is created by fusion wherein the
atoms
are forced together to form a new one. In turn, heat in excess of millions
of
degrees farenheit are produced. This activity goes on for eons until
the
point at which the nuclear fuel is exhausted. Here is where things
get
interesting. For the entire life of the star, the nuclear reaction at its
core
produced an enormous outward force. Interestingly enough, an exactly
equal
force, namely gravity, was pushing inward toward the center. The
equilibrium of
the two forces allowed the star to maintain its shape and not
break away nor
collapse. Eventually, the fuel for the star runs out, and it
this point, the
outward force is overpowered by the gravitational force, and
the object caves in
on itself. This is a gigantic implosion. Depending on the
original and final
mass of the star, several things might occur. A usual
result of such an
implosion is a star known as a white dwarf. This star has
been pressed together
to form a much more massive object. It is said that a
teaspoon of matter off a
white dwarf would weigh 2-4 tons. Upon the first
discovery of a white dwarf, a
debate arose as to how far a star can collapse.
And in the 1920’s two leading
astrophysicists, Subrahmanyan Chandrasekgar and
Sir Arthur Eddington came up
with different conclusions. Chandrasekhar looked
at the relations of mass to
radius of the star, and concluded an upper limit
beyond which collapse would
result in something called a neutron star. This
limit of 1.4 solar masses was an
accurate measurement and in 1983, the Nobel
committee recognized his work and
awarded him their prize in Physics. The
white dwarf is massive, but not as
massive as the next order of imploded star
known as a neutron star. Often as the
nuclear fuel is burned out, the star
will begin to shed its matter in an
explosion called a supernovae. When this
occurs the star loses an enormous
amount of mass, but that which is left
behind, if greater than 1.4 solar masses,
is a densely packed ball of
neutrons. This star is so much more massive that a
teaspoon of it’s matter
would weigh somewhere in the area of 5 million tons in
earth’s gravity. The
magnitude of such a dense body is unimaginable. But even
a neutron star isn’t
the extreme when it comes to a star’s collapse. That
brings us to the focus
of this paper. It is felt, that when a star is massive
enough, any where in
the area of or larger than 3-3.5 solar masses, the collapse
would cause
something of a much greater mass. In fact, the mass of this new
object is
speculated to be infinite. Such an entity is what we call a black
hole. After
a black hole is created, the gravitational force continues to pull
in space
debris and all other types of matter in. This continuous addition makes
the
hole stronger and more powerful and obviously more massive. The
simplest
three dimensional geometry for a black hole is a sphere. This type
of black hole
is called a Schwarzschild black hole. Kurt Schwarzschild was a
German
astrophysicist who figured out the critical radius for a given mass
which would
become a black hole. This calculation showed that at a specific
point matter
would collapse to an infinitely dense state. This is known as
singularity. Here
too, the pull of gravity is infinitely strong, and space
and time can no longer
be thought of in conventional ways. At singularity,
the laws defined by Newton
and Einstein no longer hold true, and a
"myterious" world of quantum
gravity exists. In the Schwarzschild black hole,
the event horizon, or skin of
the black hole, is the boundary beyond which
nothing could escape the
gravitational pull. Most black holes would tend to
be in a consistent spinning
motion, because of the original spin of the star.
This motion absorbs various
matter and spins it within the ring that is
formed around the black hole. This
ring is the singularity. The matter keeps
within the Event Horizon until it has
spun into the center where it is
concentrated within the core adding to the
mass. Such spinning black holes
are known as Kerr Black Holes. Roy P. Kerr, an
Australian mathematician
happened upon the solution to the Einstein equations
for black holes with
angular momentums. This black hole is very similar to the
previous one. There
are, however, some differences which make it more viable for real, existing
ones. The singularity in the this hole is more time-like, while
the other is
more space-like. With this subtle difference, objects would be able
to enter
the black whole from regions away from the equator of the event horizon
and
not be destroyed. The reason it is called a black hole is because any
light
inside of the singularity would be pulled back by the infinite gravity
so that
none of it could escape. As a result anything passing beyond the
event horizon
would dissappear from sight forever, thus making the black hole
impossible for
humans to see without using technologicalyl advanced
instruments for measuring
such things like radiation. The second part of the
name referring to the
"hole" is due to the fact that the actual hole, is
where everything is
absorbed and where the center core presides. This core is
the main part of the
black hole where the mass is concentrated and appears
purely black on all
readings even through the use of radiation detection
devices. The first
scientists to really take an in depth look at black holes
and the collapsing of
stars, were a professor, Robert Oppenheimer and his
student Hartland Snyder, in
the early nineteen hundreds. They concluded on
the basis of Einstein's theory of
relativity that if the speed of light was
the utmost speed over any massive
object, then nothing could escape a black
hole once in it's clutches. It should
be noted, all of this information is
speculation. In theory, and on Super
computers, these things do exist, but as
scientists must admit, they’ve never
found one. So the question arises, how
can we see black holes? Well, there are
several approaches to this question.
Obviously, as realized from a previous
paragraph, by seeing, it isn’t
necessarily meant to be a visual
representation. So we’re left with two
approaches. The first deals with X-ray
detection. In this precision measuring
system, scientists would look for areas
that would create enormous shifts in
energy levels. Such shifts would result
from gases that are sucked into the
black hole. The enormous jolt in gravitation
would heat the gases by millions
of degrees. Such a rise could be evidence of a
black hole. The other means of
detection lies in another theory altogether. The
concept of gravitational
waves could point to black holes, and researchers are
developing ways to read
them. Gravitational Waves are predicted by Einstein’s
General Theory of
Relativity. They are perturbations in the curvature of
spacetime. Sir Arthur
Eddington was a strong supporter of Einstein, but was
skeptical of gravity
waves and is reported to have said, "Graviatational
waves propagate at the
speed of thought." But what they are is important to
a theory. Gravitational
waves are enormous ripples eminating from the core of
the black hole and
other large masses and are said to travel at the speed of
light, but not
through spacetime, but rather as the backbone of spacetime
itself. These
ripples pass straight through matter, and their strength weakens
as it gets
farther from the source. The ripples would be similar to a stone
dropped in
water, with larger ones toward the center and fainter ones along the
outer
circumference. The only problem is that these ripples are so minute
that
detecting them would require instrumentation way beyond our
present
capabilities. Because they’re unaffected by matter, they carry a pure
signal,
not like X-rays which are diffused and distorted. In simulations the
black hole
creates a unique frequency known as it natural mode of vibrations.
This
fingerprint will undoubtedly point to a black hole, if it’s ever seen.
Just
recently a major discovery was found with the help of The Hubble
Space
Telescope. This telescope has just recently found what many
astronomers believe
to be a black hole, after being focused on a star
orbiting an empty space.
Several picture were sent back to Earth from the
telescope showing many computer
enhanced pictures of various radiation
fluctuations and other diverse types of
readings that could be read from the
area in which the black hole is suspected
to be in. Because a black hole
floats wherever the star collapsed, the truth is,
it can vastly effect the
surrounding area, which might have other stars in it.
It could also
absorb a star and wipe it out of existance. When a black hole
absorbs a star,
the star is first pulled into the Ergosphere, this is the area
between the
event horizon and singularity, which sweeps all the matter into the
event
horizon, named for it's flat horizontal appearance and critical
properties
where all transitions take place. The black hole doesn’t just pull
the star in
like a vaccuum, rather it creates what is known as an accretion
disk which is a
vortex like phenomenom where the star’s material appears to
go down the drain
of the black hole. When the star is passed on into the
event horizon the light
that the star ordinarily gives off builds inside the
ergosphere of the black
hole but doesn’t escape. At this exact point in time,
high amounts of
radiation are given off, and with the proper equipment, this
radiation can be
detected and seen as an image of emptiness or as preferred,
a black hole.
Through this technique astronomers now believe that they
have found a black hole
known as Cygnus X1. This supposed black hole has a
huge star orbiting around it,
therefore we assume there must be a black hole
that it is in orbit with. Science
Fiction has used the black hole to come
up with several movies and fantastical
events related to the massive beast.
Tales of time travel and of parallel
universes lie beyond the hole. Passing
the event horizon could send you on that
fantastical trip. Some think there
would be enough gravitational force to
possible warp you to an end of the
universe or possibly to a completely
different one. The theories about what
could lie beyond a black hole are
endless. The real quest is to first find
one. So the question remains, do they
exist? Black holes exist, unfortunately
for the scientific community, their life
is restricted to formulas and super
computers. But, and there is a but, the
scientific community is relentless in
their quest to build a better means of
tracking. Already the advances of
hyper-sensitive equipment is showing some good
signs, and the accuracy will
only get better.