Big Bang TheoryIt 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
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
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
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
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.
1. Dinah L. Mache, Astronomy, New York: John Wiley ; Sons,
Inc., 1987. p. 128.
2. Ibid., p. 130.
3. Joseph Silk, The Big Bang, New York: W.H. Freeman and
Company, 1989. p. 60.
4. Terry Holt, The Universe Next Door, New York: Charles
Scribner’s Sons, 1985. p. 326.
5. Ibid., p. 327.
6. Charles J. Caes, Cosmology, The Search For The Order Of
The Universe, USA: Tab Books Inc., 1986. p. 72.
7. John Gribbin, In Search Of The Big Bang, New York: Bantam
Books, 1986. p. 273.
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
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.,
Silk, Joseph. The Big Bang. New York: W.H. Freeman and Company,