|
|
 |
Essay on Big Bang
| Date: |
08-30-03 4:22am |
| Subject: |
Science |
| Word Count: |
1151 |
| Page Count: |
4.6 |
Big Bang
The Big Bang Theory
The Big Bang Theory It is always a mystery about how the universe began, whether if and
when it will end. Astronomers construct hypotheses called cosmological models that try to
find the answer. There are two types of models: Big Bang and Steady State. However,
through many observational evidences, the Big Bang theory can best explain the creation
of the universe. The Big Bang model postulates that about 15 to 20 billion years ago, the
universe violently exploded into being, in an event called the Big Bang. Before the Big
Bang, all of the matter and radiation of our present universe were packed together in the
primeval fireball—an extremely hot dense state from which the universe rapidly
expanded.1 The Big Bang was the start of time and space. The matter and radiation of
that early stage rapidly expanded and cooled. Several million years later, it condensed into
galaxies. The universe has continued to expand, and the galaxies have continued moving
away from each other ever since. Today the universe is still expanding, as astronomers
have observed. The Steady State model says that the universe does not evolve or change
in time. There was no beginning in the past, nor will there be change in the future. This
model assumes the perfect cosmological principle. This principle says that the universe is
the same everywhere on the large scale, at all times.2 It maintains the same average
density of matter forever. There are observational evidences found that can prove the Big
Bang model is more reasonable than the Steady State model. First, the redshifts of distant
galaxies. Redshift is a Doppler effect which states that if a galaxy is moving away, the
spectral line of that galaxy observed will have a shift to the red end. The faster the galaxy
moves, the more shift it has. If the galaxy is moving closer, the spectral line will show a
blue shift. If the galaxy is not moving, there is no shift at all. However, as astronomers
observed, the more distance a galaxy is located from Earth, the more redshift it shows on
the spectrum. This means the further a galaxy is, the faster it moves. Therefore, the
universe is expanding, and the Big Bang model seems more reasonable than the Steady
State model. The second observational evidence is the radiation produced by the Big
Bang. The Big Bang model predicts that the universe should still be filled with a small
remnant of radiation left over from the original violent explosion of the primeval fireball in
the past. The primeval fireball would have sent strong shortwave radiation in all directions
into space. In time, that radiation would spread out, cool, and fill the expanding universe
uniformly. By now it would strike Earth as microwave radiation. In 1965 physicists Arno
Penzias and Robert Wilson detected microwave radiation coming equally from all
directions in the sky, day and night, all year.3 And so it appears that astronomers have
detected the fireball radiation that was produced by the Big Bang. This casts serious doubt
on the Steady State model. The Steady State could not explain the existence of this
radiation, so the model cannot best explain the beginning of the universe. Since the Big
Bang model is the better model, the existence and the future of the universe can also be
explained. Around 15 to 20 billion years ago, time began. The points that were to become
the universe exploded in the primeval fireball called the Big Bang. The exact nature of this
explosion may never be known. However, recent theoretical breakthroughs, based on the
principles of quantum theory, have suggested that space, and the matter within it, masks
an infinitesimal realm of utter chaos, where events happen randomly, in a state called
quantum weirdness.4Before the universe began, this chaos was all there was. At some
time, a portion of this randomness happened to form a bubble, with a temperature in
excess of 10 to the power of 34 degrees Kelvin. Being that hot, naturally it expanded. For
an extremely brief and short period, billionths of billionths of a second, it inflated. At the
end of the period of inflation, the universe may have a diameter of a few centimetres. The
temperature had cooled enough for particles of matter and antimatter to form, and they
instantly destroy each other, producing fire and a thin haze of matter-apparently because
slightly more matter than antimatter was formed.5 The fireball, and the smoke of its
burning, was the universe at an age of trillionth of a second. The temperature of the
expanding fireball dropped rapidly, cooling to a few billion degrees in few minutes. Matter
continued to condense out of energy, first protons and neutrons, then electrons, and finally
neutrinos. After about an hour, the temperature had dropped below a billion degrees, and
protons and neutrons combined and formed hydrogen, deuterium, helium. In a billion
years, this cloud of energy, atoms, and neutrinos had cooled enough for galaxies to form.
The expanding cloud cooled still further until today, its temperature is a couple of degrees
above absolute zero. In the future, the universe may end up in two possible situations.
From the initial Big Bang, the universe attained a speed of expansion. If that speed is
greater than the universe’s own escape velocity, then the universe will not stop its
expansion. Such a universe is said to be open. If the velocity of expansion is slower than
the escape velocity, the universe will eventually reach the limit of its outward thrust, just
like a ball thrown in the air comes to the top of its arc, slows, stops, and starts to fall. The
crash of the long fall may be the Big Bang to the beginning of another universe, as the
fireball formed at the end of the contraction leaps outward in another great expansion.6
Such a universe is said to be closed, and pulsating. If the universe has achieved escape
velocity, it will continue to expand forever. The stars will redden and die, the universe will
be like a limitless empty haze, expanding infinitely into the darkness. This space will
become even emptier, as the fundamental particles of matter age, and decay through time.
As the years stretch on into infinity, nothing will remain. A few primitive atoms such as
positrons and electrons will be orbiting each other at distances of hundreds of
astronomical units.7 These particles will spiral slowly toward each other until touching,
and they will vanish in the last flash of light. After all, the Big Bang model is only an
assumption. No one knows for sure that exactly how the universe began and how it will
end. However, the Big Bang model is the most logical and reasonable theory to explain
the universe in modern science.
Bibliography
Boslough, John. Stephen Hawking’s Universe. New York: Cambridge University Press,
1980. Caes, J. Charles. Cosmology, The Search For The Order Of The Universe. USA:
Tab Books Inc., 1986. Gribbin, John. In Search Of The Big Bang. New York: Bantam
Books, 1986. Holt, Terry. The Universe Next Door. New York: Charles Scribner’s Sons,
1985. Kaufmann, J. William III. Astronomy: The Structure Of The Universe. New York:
Macmillan Publishing Co., Inc., 1977. Mache, L. Dinah. Astronomy. New York: John
Wiley & Sons, Inc., 1987. Silk, Joseph. The Big Bang. New York: W.H. Freeman and
Company, 1989.
Science Essays
Complete List:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|