This essay The Universe has a total of 1257 words and 8 pages.
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
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
Topics Related to The Universe
Physical cosmology, Big Bang, Universe, Steady State theory, Chronology of the universe, Cosmology, Metric expansion of space, Inflation, Future of an expanding universe, Astronomy, Cosmic microwave background, Age of the universe, steady state model, big bang theory, observational evidences, primeval fireball, distant galaxies, cosmological principle, doppler effect, creation of the universe, cosmological models, bang model, density of matter, spectral line, redshifts, blue shift, postulates, time and space, hypotheses, million years, galaxy, large scale
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