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 Re: Creation of a Cosmology:THE BIG BANG THEORY (Re: sentimental)
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As astronomers were collecting data on the Universe based on their observations, theorists were busy developing models that attempted to explain the cosmos. Recently equipped with Albert Einstien's Theory of Relativity, Einstein was one of the first to attempt an explanation of the physical Universe. Einstein believed the Universe to have a static, uniform, isotropic distribution of matter. Einstein's own calculations however proved to result in the exact opposite, an oscillating universe that had the potential for expansion or contraction. He was certain that the universe was stable. Einstein was compelled to amend his original equation. He used the term cosmological constant, which created a spherical, four-dimensional closed universe (Parker).
Around the same time the Dutch astronomer Willem deSitter used Einstein's general theory of relativity to develop his own model of the Universe. His model was unique in that it did not take into consideration the existence of matter in the Universe. However it did go beyond Einstein's model in that it predicted the redshift, even though de Sitter felt it was an illusion, and did not at the time link it to any recession of celestial objects. The academic community of 1930 did not fully embrace either model of the universe. Then the Secretary of the Royal Astronomical Society in England was made aware that three years previous, one of his students had written a theory of the universe independent of the two major forces in cosmological theory. Georges Lemaître created a cosmology that predicted a universe that was forever in a state of expansion. When this theory was rejuvenated by its republication in the journal Monthly Notices, it brought to the table another similar theory that was devised ten years earlier. Aleksander Friedmann, a Russian mathematician, analyzed Einstein's cosmological constant that produced a static universe. Friedmann proved that there are three possibilities for the universe when the cosmological constant is zero. If the matter in the universe is greater than the critical density, the universe would ultimately collapse back onto itself. If the inverse is correct the universe would expand forever. If the universe were flat with a constant of zero at critical density, the universe would again expand infinitely. Both Lemaître and Friedmann's solutions were analyzed by Einstein and were summarily dismissed. It was not until Hubble had proved that galaxies were in fact receding in 1932 that Einstein was forced to drop his static universe model. The observational proof that the universe was expanding, combined with the models of Friedmann and Lemaître that predicted an expanding universe unified the cosmologist and the astronomer in agreement. The only question remained was if the universe is expanding, what was the origination of this expansion? Lemaître used the second law of thermodynamics as his starting point. Based on the assumption that the expansion of the universe was an increase in the disorder of a system, originating from a singularity of neutrons, this primordial nucleus would then explode where an increase in the entropy of the universe would be apparent. On May 9, 1931, Lemaître published his theory of the universe in the journal Nature and it was met with general skepticism (Parker).
George Gamow expounded on Lemaître's work, using recent discoveries in quantum theory. Lemaître formulated his model based on the theory that a giant nucleus began to entropy, breaking down into individual constituents. Gamow believed that a nucleus containing not only neutrons but protons and electrons as well was the starting point. Due to the very high amount of radiant energy in the early universe, temperature would be in excess of one billion degrees Kelvin. At five minutes old, Gamow speculated, this universe would have particles that could not combine. But as the expansion began the temperatures would decrease and nuclear fusion would occur. Atoms would form as protons and neutrons would attach themselves to one another. Gamow then Hypothesized that all the elements in the Universe were created at this time. One year later however, it was proven that Gamow's math didn't stand up to scrutiny as it was shown that atomic mass 5 could not have been created from this primordial nucleus, as well as mass 8 (Gribbin).
Although all of the elements in the universe were proven not to have originated from the Primordial Fireball, the theory gained momentum until it received a worthy adversarial cosmology known as the Steady State Theory. Fred Hoyle (who despairingly coined the term Big Bang) and his colleagues constructed a model of the universe that was widely accepted for religious reasons if not so much for its scientific hypothesis. Hoyle suggested that the universe is infinitely old and has remained in a steady state except that the universe was indeed expanding. However galaxies are not receding from one another but space is constantly being created between galaxies. In order for the average density to remain constant, Hoyle suggested that matter had to be created in these new areas where space was expanding. Only one hydrogen atom needed to be created every year in an area the size of a 100 meter cube to account for the expansion. This spontaneous generation of matter Hoyle argues would allow for the formation of new galaxies between ancient ones and the Universe would maintain its steady state. It would then follow that astronomers would be able to detect young galaxies in the midst's of very old ones. This was one of the many inconsistencies that were found with the Steady State Theory. In the 1950's Steady State Theorists took a heavy blow when radio galaxies were discovered showing that, consistent with big bang Cosmology, galaxies evolved and were very active billions of years ago (Parker).
Finally the empirical evidence big bangers had predicted was observed in 1965 by Bell Labs Arno Penzias and Robert Wilson. Robert Dicke of Princeton University was the first to search for fossil remains of the big bang. Dicke suggested that the Big bang emanated from a previous universe and that a temperature in excess of one billion degrees was necessary to create our new universe. This energy would in turn produce an infinitesimal amount of radiation that should be measurable to this day. Based on Planck's law that all bodies emit energy that can be documented on an electromagnetic diagram. Depending on the length of the wave they can register anywhere from X rays to radio waves and everything in between. A bodies emission of energy is contingent upon the constituent elements of the body, the amount of surface area of the body and the surface temperature of the body. The body that emits the greatest amount of energy is a so called black body. Using Planck's Black Body Curve as a guide Dicke theorized that the Cosmic Background Radiation of the Big Bang should be about 3° above absolute zero. Dicke's colleague Jim Peebles also concluded that when the Fireball's remnants cooled to 3000° Kelvin nuclei would be able to form and helium was able to form from hydrogen. This left a universe with a mixture of approximately 75% hydrogen and 25% helium, resembling the same amount of helium found in the Sun. Peebles concluded that since the two most abundant elements in the universe were created when the Universe was at 3000° K and since then the universe has expanded by a factor of 1000 the radiation from the Big Bang should have a temperature of about 10° K. Later refinements to these equations revised the estimated temperature to 3° K. Dicke and Peebles were confident that there instruments would be the first to detect this Cosmic Background Radiation (Parker). At the same time Penzias and Wilson were busy attempting to measure radiation from the Milky Way Galaxy. They were narrowing in on their source when they were left with a noise that was interfering with their signal. This noise originated from cosmic radiation and had a temperature of 3°K. It seemed to be coming in from all directions and never fluctuated. With their original research corrupted due to the unexplained noise they resigned themselves to writing a paper on this unexplainable phenomenon. Months later Penzia's discovered that Peebles group was searching for this relic radiation without success. Upon further examination they realized that Penzia and Wilson had stumbled upon the single most important discovery that confirmed the Primordial big bang Explosion(Parker).
Big Bang theorists made several predictions that have eventually supported the theory. The first is Hubble's observation of the redshift-distance relationship. This relationship enables us to approximate the age of the universe with the help of three separate celestial bodies that all arrive at the same relative result. Hubble used what is known as "standard candles" to build a "cosmic distance ladder." By knowning the distance of certain celestial bodies he would be able to incrementally construct an age for the Universe. These standard candles were: cepheid variables in neighborhood galaxies; bright stars in more distant galaxies and in galaxies millions of parsecs away, the brightness of the galaxy itself was used as a standard candle (Maffei)
Central to the question of the age of the Universe are two important theoretical terms. The Hubble Constant refers to how fast the velocities of the galaxies increase with their distance from the Earth. There is quite a raging debate on the value of this constant ranging from 50 Km/sec per Mpc (Mpc is a Megaparsec, about 3 million light years) to 100 Km/sec per Mpc. This explains the disparity in the ± 5 billion year estimate for the age of the universe. The other constant of importance is known as q that defines the deceleration of the expansion of the universe. Depending on the critical density of the universe that this q constant is based, the universe will prove to be either infinitely expanding as in the flat and open models, or an oscillating closed universe; a big crunch/big bang universe that will ultimately condense back into a singularity and begin the process all over again(Weinberg). Hubble's succesor Allan Sandage predicted a closed universe when he plotted a number of radio galaxies many billions of light years away. The evidence for this closed universe was quickly challanged a few years later and eventually fell out of favor. To this day the Hubble Constant and the q constant remain the two most important unanswered problems in modern cosmology.
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