Big Bang Theory Essay, Research Paper

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.4

Before 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.