The Big Bang (Comparisive Of Two Major Theories) Essay, Research Paper
Big Bang
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. 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. 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. 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 know. However, recent
theoretical breakthroughs, based on the principles of quantum theory, have suggested that
space, and the matter within it, masks an infinitesimal realm or utter chaos, where events
happen randomly, in a state called quantum weirdness.
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 exploded. For an extremely brief and
short period, billionths and billionths of a second, it inflated. At the end of this 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 destroyed
each other, producing fire and a thin haze of matter apparently because slightly more
matter than antimatter was formed. The fireball, and the smoke of its buring, was the
universe at an age of a trillionth a second.
The temperature of the expanding fireball dropped rapidly, cooling to a few billion
degrees in a 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, and 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. 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. 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. Man will never know the exact truth
about the roots of our universe, however, the Big Bang model is the most logical and
reasonable theory to explain the universe in modern science.