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The Birth of the Universe

The Big Bang Theory

Abigail Sequeira

on 7 November 2012

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Transcript of The Birth of the Universe

What is the Big Bang Theory? 3. About three seconds after the initial explosion, nucleosynthesis set in to form simple elements, such as hydrogen and helium. Nearly one billion years later, expansion slowed down enough for gravity to condense clumps of these elements together. These clumps were gravitationally pulled towards other clumps and eventually formed galaxies. From there, the universe continued to expand and cool down, resulting in its present diluted state. The Birth of the Universe? The Big Bang Theory 1. The Big Bang Theory states that at some point in the distant past, there was nothing. At approximately 13.7 billion years ago, a violent explosion occurred and the universe, in an extremely hot and dense state, expanded in all directions in that instant. This super fast expansion was known as inflation and was caused by an unexplained push of energy. 2. Inflation had pushed out the fabric of space and time, and from there, the universe continued to expand, but not as rapidly. During this slower rate of expansion, fundamental forces and particles were formed. The basic forces of nature were gravity, strong nuclear force, weak nuclear force, and electromagnetic energy. The basic particles were quarks, electrons, photons, and neutrinos. Why does the Big Bang Theory work? The basic particles formed during the early stages of the Big Bang eventually combined to form huge numbers of Hydrogen, Helium and Lithium nuclei. The process of forming all these nuclei is called nucleosynthesis. The observed abundances of these elements throughout the universe closely match the calculated predictions for the formation of these elements from nucleosynthsis in the first minutes of the universe. Therefore, nucleosynthesis works to prove the verity of the Big Bang Theory. In 1964, two astronomers, Arno Penzias and Robert Wilson, in an attempt to detect microwaves from outer space, inadvertently discovered a noise of extraterrestrial origin. The noise did not seem to emanate from one location but instead, it came from all directions at once. It became obvious that what they heard was radiation from the farthest reaches of the universe which had been left over from the Big Bang. This discovery of the radioactive aftermath of the initial explosion proved the Big Bang theory true. In 1929, Edwin Hubble discovered that a galaxy's velocity is proportional to its distance. For example, galaxies that are twice as far from us move twice as fast. Hubble made the observation that the universe is continuously expanding in every direction. This observation means that it has taken every galaxy the same amount of time to move from a common starting position to its current position. Just as the Big Bang provided for the foundation of the universe, Hubble’s observations provided for the foundation of the Big Bang theory. 4. Depending on its density, the universe can come to end in a variety of ways. The death of the universe can be determined by the ratio of its observed density to its critical density (the amount of matter that will halt the expansion of the universe) and is represented by the Greek letter omega. If omega is less than one, the Universe will continue expanding until it is so large that it dies a cold death. If omega equals one the Universe will eventually stop expanding but will also die a cold static death. But, if omega is greater than one, then the Universe is doomed to collapse under it's own gravitational mass, and will die a hot, fiery death in a Big Crunch. Evidence against the Big Bang Another problem has to do with the strongest supporting evidence; cosmic microwave background radiation. In order for the universe to produce the galaxies we see around us, the fluctuations found in the background radiation indicate that there must be a hundred times more dark matter than visible matter. But there is no experimental or observable evidence that dark matter exists. It's a theory to make the Big Bang work. So if there is no dark matter, the theory falsely predicts that galaxies do not exist. Observations suggest that the expansion of the universe appears to be accelerating, a fact that is not yet explained and may call for modifications of the Big Bang theory. The theory predicts that the universe, on the large scale that it exists, should be smooth and homogeneous. However, the universe is clumpy. Alternative Theories Steady State Theory The theory states that the universe is uniform throughout both time and space. However, the discovery of cosmic microwave background, the leftover radiation from the Big Bang, could not be explained by the Steady State theory. In time, this theory died out in favor of the Big Bang. Inflationary Theory This theory states that the Universe, due to properties of elementary particles not accounted for in the standard Big Bang model, expanded for a fleeting instant at its beginning at a much higher rate than that expected. This quick and astonishing rate of expansion happened as a result of the gravitational repulsion of a false vacuum (a type of radioactive matter) that filled the universe during a small fraction of a second of its early history. Why is the Big Bang Theory the most plausible theory? Many aspects on the evolution of our universe are well-explained by the Big Bang model, which is why it is almost universally accepted as the most reasonable theory for the origin and evolution of the universe. Furthermore, the expansion of the universe indicates that the universe was extremely small at some point. Something had caused the expansion, and that something was the Big Bang. The idea of a false vacuum in many ways corrected the flaws of the Big Bang. However, while inflation has many attractive features, it is not yet a proven theory because many of the details still do not work out right in realistic calculations without making poorly justified assumptions. This theory is in need of further investigation, or more proof, in order to truly right the wrongs of the Big Bang.
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