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165 lines
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___ ___ ___
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___|: |___|: \ ___|: \ DizDate: 12/95
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_______\___ \___ \___ ___\_______ WordCount: 1313
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«¬¬¬¬¬¬| |: | |____| ___|¬¬¬¬¬¬«
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«¬¬¬¬¬| | |: | |: |¬¬¬¬¬« Subject/Topic is on:
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«¬¬¬¬| |: | |: | |¬¬¬¬« [Big Bang Model ]
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----\___|: |\__ |\__ |---- [ ]
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`, a c e ,` [ ]
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`, e s s a y s ,` [ ]
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Grade Level: [ ]Grade School Type of Work: [x]Essay/Report/Term
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[x]High School [ ]Informational
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[ ]College [ ]Notes
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[ ]Misc
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ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>Chop Here>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ
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It is always a mystery about how the universe began, whether if and
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when it will end. Astronomers construct hypotheses called cosmological
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models that try to find the answer. There are two types of models: Big
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Bang and Steady State. However, through many observational evidences, the
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Big Bang theory can best explain the creation of the universe.
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The Big Bang model postulates that about 15 to 20 billion years ago,
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the universe violently exploded into being, in an event called the Big
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Bang. Before the Big Bang, all of the matter and radiation of our present
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universe were packed together in the primeval fireball--an extremely hot
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dense state from which the universe rapidly expanded.1 The Big Bang was
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the start of time and space. The matter and radiation of that early stage
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rapidly expanded and cooled. Several million years later, it condensed
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into galaxies. The universe has continued to expand, and the galaxies have
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continued moving away from each other ever since. Today the universe is
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still expanding, as astronomers have observed.
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The Steady State model says that the universe does not evolve or
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change in time. There was no beginning in the past, nor will there be
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change in the future. This model assumes the perfect cosmological
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principle. This principle says that the universe is the same everywhere on
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the large scale, at all times.2 It maintains the same average density of
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matter forever.
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There are observational evidences found that can prove the Big Bang
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model is more reasonable than the Steady State model. First, the redshifts
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of distant galaxies. Redshift is a Doppler effect which states that if a
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galaxy is moving away, the spectral line of that galaxy observed will have
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a shift to the red end. The faster the galaxy moves, the more shift it has.
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If the galaxy is moving closer, the spectral line will show a blue shift.
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If the galaxy is not moving, there is no shift at all. However, as
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astronomers observed, the more distance a galaxy is located from Earth, the
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more redshift it shows on the spectrum. This means the further a galaxy is,
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the faster it moves. Therefore, the universe is expanding, and the Big Bang
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model seems more reasonable than the Steady State model.
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The second observational evidence is the radiation produced by the Big
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Bang. The Big Bang model predicts that the universe should still be filled
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with a small remnant of radiation left over from the original violent
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explosion of the primeval fireball in the past. The primeval fireball
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would have sent strong shortwave radiation in all directions into space.
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In time, that radiation would spread out, cool, and fill the expanding
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universe uniformly. By now it would strike Earth as microwave radiation.
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In 1965 physicists Arno Penzias and Robert Wilson detected microwave
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radiation coming equally from all directions in the sky, day and night, all
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year.3 And so it appears that astronomers have detected the fireball
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radiation that was produced by the Big Bang. This casts serious doubt on
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the Steady State model. The Steady State could not explain the existence
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of this radiation, so the model cannot best explain the beginning of the
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universe.
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Since the Big Bang model is the better model, the existence and the
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future of the universe can also be explained. Around 15 to 20 billion
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years ago, time began. The points that were to become the universe
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exploded in the primeval fireball called the Big Bang. The exact nature of
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this explosion may never be known. However, recent theoretical
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breakthroughs, based on the principles of quantum theory, have suggested
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that space, and the matter within it, masks an infinitesimal realm of utter
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chaos, where events happen randomly, in a state called quantum weirdness.4
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Before the universe began, this chaos was all there was. At some
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time, a portion of this randomness happened to form a bubble, with a
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temperature in excess of 10 to the power of 34 degrees Kelvin. Being that
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hot, naturally it expanded. For an extremely brief and short period,
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billionths of billionths of a second, it inflated. At the end of the
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period of inflation, the universe may have a diameter of a few centimetres.
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The temperature had cooled enough for particles of matter and antimatter to
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form, and they instantly destroy each other, producing fire and a thin haze
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of matter-apparently because slightly more matter than antimatter was
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formed.5 The fireball, and the smoke of its burning, was the universe at
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an age of trillionth of a second.
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The temperature of the expanding fireball dropped rapidly, cooling to
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a few billion degrees in few minutes. Matter continued to condense out of
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energy, first protons and neutrons, then electrons, and finally neutrinos.
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After about an hour, the temperature had dropped below a billion degrees,
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and protons and neutrons combined and formed hydrogen, deuterium, helium.
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In a billion years, this cloud of energy, atoms, and neutrinos had cooled
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enough for galaxies to form. The expanding cloud cooled still further
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until today, its temperature is a couple of degrees above absolute zero.
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In the future, the universe may end up in two possible situations.
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From the initial Big Bang, the universe attained a speed of expansion. If
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that speed is greater than the universe's own escape velocity, then the
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universe will not stop its expansion. Such a universe is said to be open.
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If the velocity of expansion is slower than the escape velocity, the
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universe will eventually reach the limit of its outward thrust, just like a
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ball thrown in the air comes to the top of its arc, slows, stops, and
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starts to fall. The crash of the long fall may be the Big Bang to the
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beginning of another universe, as the fireball formed at the end of the
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contraction leaps outward in another great expansion.6 Such a universe is
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said to be closed, and pulsating.
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If the universe has achieved escape velocity, it will continue to
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expand forever. The stars will redden and die, the universe will be like a
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limitless empty haze, expanding infinitely into the darkness. This space
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will become even emptier, as the fundamental particles of matter age, and
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decay through time. As the years stretch on into infinity, nothing will
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remain. A few primitive atoms such as positrons and electrons will be
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orbiting each other at distances of hundreds of astronomical units.7 These
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particles will spiral slowly toward each other until touching, and they
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will vanish in the last flash of light. After all, the Big Bang model is
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only an assumption. No one knows for sure that exactly how the universe
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began and how it will end. However, the Big Bang model is the most logical
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and reasonable theory to explain the universe in modern science.
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ENDNOTES
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1. Dinah L. Mache, Astronomy, New York: John Wiley & Sons,
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Inc., 1987. p. 128.
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2. Ibid., p. 130.
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3. Joseph Silk, The Big Bang, New York: W.H. Freeman and
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Company, 1989. p. 60.
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4. Terry Holt, The Universe Next Door, New York: Charles
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Scribner's Sons, 1985. p. 326.
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5. Ibid., p. 327.
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6. Charles J. Caes, Cosmology, The Search For The Order Of
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The Universe, USA: Tab Books Inc., 1986. p. 72.
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7. John Gribbin, In Search Of The Big Bang, New York: Bantam
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Books, 1986. p. 273.
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BIBLIOGRAPHY
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Boslough, John. Stephen Hawking's Universe. New York: Cambridge
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University Press, 1980.
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Caes, J. Charles. Cosmology, The Search For The Order Of The
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Universe. USA: Tab Books Inc., 1986.
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Gribbin, John. In Search Of The Big Bang. New York: Bantam
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Books, 1986.
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Holt, Terry. The Universe Next Door. New York: Charles
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Scribner's Sons, 1985.
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Kaufmann, J. William III. Astronomy: The Structure Of The
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Universe. New York: Macmillan Publishing Co., Inc., 1977.
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Mache, L. Dinah. Astronomy. New York: John Wiley & Sons, Inc.,
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1987.
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Silk, Joseph. The Big Bang. New York: W.H. Freeman and Company,
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1989.
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