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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.
Science Essays
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