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Big Bang Cosmology Introduction to Big Bang Theory Einstein came up with The Big Bang Theory with the intention of creating a model of the universe in which both his General Theory of relativity worked and the rest of the universe still worked. He based his theory on a fairly uniform distribution of mass throughout the universe. His Big Bang Theory was able to fix the peculiar way that Mercury Orbited the Sun and it was able to fix the way the Sun bent light. These were the first problems that it fixed but there have been many more over the years. Einstein's Big Bang theory provides cosmologists with the ability to effectively travel back in time. The theory of special relativity postulates that the velocity of light is both finite and constant, namely, 3? 1010 centimeters per second, as already mentioned (equal to 186, 000 miles per second).
Moreover, a very surprising aspect of the travel of light is that its velocity is independent of the velocity both of the emitting light source and also of the observer. As far as we know, the most rapid possible way to transmit information is at the velocity of light. For example, the Sun is at a distance from Earth of about 93 million miles. If the Sun were to be snuffed out suddenly, we would not know it until light no longer reached us, and this would take about eight minutes (dividing the distance of the Sun, 93, 000, 000 miles, by 186, 000 miles per second the velocity of light, gives about 500 seconds or 8. 3 minutes). It takes about four years for light to reach us from the star nearest the Sun. If the universe is assumed to be about 15 billion years old and was somehow producing light from a time near the Big Bang, then we could in principle observe at most only to a distance of 15 billion light years (i.
e. , 15 billion ye inconsistent in the assumption of homogeneity and isotropy on a scale of, say, 300 million light years... The Evolution of the Universe A universe that is expanding is a universe with a clear path into the past. If things are now far apart, they must at one point have been close together; and if things were once close together, they must at one point have been hotter than they are now, the contraction of space acting to compress its constituents like a vise, and so increase their energy. The retreat into the past ends at an initial singularity, a state in which material particles are at no distance from each other and the temperature, density, and curvature of the universe are infinite.
The astronomy may now be observed crawling back up the cliffs of time he so recently descended. During the first 10 - 43 seconds after the Big Bang 10 - 43 is one over a ten followed by 42 zeros -- both matter and radiation fill the void. A reign of fluid interchange obtains, with particles of matter and antimatter exchanging identities. As the primitive goo of the cosmos, the primordial stuff continues to expand, it continues to cool. Neutrinos, photons, electrons, positrons, neutrons, and protons agitate themselves throughout space.
With the temperature dropping, the neutrinos decamp for parts unknown. At roughly one-and-one-half seconds after the Big Bang, protons and neutrons lose the ability to exchange identities, and the ratio of neutrons to protons in the universe freezes itself at one to six. Three-and-one-half seconds later, the equilibrium between electrons and positrons collapses, and the positrons follow the neutrinos into the void. Three minutes pass. The era of nucleosynthesis begins thereafter. Those neutrons that during the freeze-out found themselves bound to the world's vagrant protons now take up an identity as a form of helium.
Other elements wait patiently for the stars to be born so that they may be cooked in their interiors. The universe continues to expand, pulse, glow, throb, and moan for 400, 000 years more, passing insensibly from a place where radiation predominates to an arena where matter has taken charge and is in command. The temperature is now 4, 000 degrees Kelvin. The great era of recombination is at hand, a burst of cosmic creativity recorded in the walls of time. Free electrons and protons form hydrogen. The interaction between matter and radiation changes dramatically.
Until recombination, photons found themselves trapped within a cosmic pinball machine, ricocheting from one free charged particle to another, the cosmos frustratingly opaque because frustratingly dense. But hydrogen binds the cosmic debris, and for the first time, light streams from one side of creation to the other. The early universe fills with low-temperature blackbody radiation, the stuff destined to be observed fifteen billion years later in Princeton, New Jersey, as cosmic background radiation (CBR). The separation of light and matter allows the galaxies to form, gravity binding the drifting dust in space.
At last, the universe fills with matter, the stars settling into the sky, the far-flung suns radiating energy, the galaxies spreading themselves throughout the heavens. On the earth that has been newly made, living things shamble out of the warm oceans, the cosmic archeologist himself finally clambering over the lip of time to survey the scene and take notes on all that has occurred. Evidence Although the physical and astronomical evidence for the current Big Bang model of the universe is convincing to most cosmologists, some pieces of evidence may be less direct than others. Indirect but significant evidence is found in the observation that on a large scale, many millions of light years in extent, the universe appears to be homogeneous and isotropic, concepts that we have already mentioned. This, together with the universality of the nuclear composition of the universe on a large scale, suggests a common origin for its major features. It is important to realize that after Einstein introduced the theory of general relativity, it was found to incorporate non static models of the universe.
This alteration in Einstein's original assertions was developed in the 1920 s by the mathematician Alexander Friedmann in what was then the USSR, by the cosmologist and cleric Georges Lemaitre in Belgium, and by the astronomer Willem de Sitter in the Netherlands. Their work, which has since provided the basis for modeling the large-scale structure of the universe, argues against a static or unchanging universe and for a dynamic or evolving universe, one that expands, or expands and then contracts, or goes through a series of expansions and contractions (i. e. , oscillations) all characterized as evolutionary. Other phenomena also suggest an evolving universe. Modern observational techniques enable one to estimate the age of the chemical elements from the present existence and relative amounts of radioactive nuclear species. The radioactive species uranium, thorium, and others exist in nature and undergo spontaneous decay (nuclear transformation) at a precisely measurable rate, from one type of nucleus to another, usually through a sequence of steps culminating in a nucleus that is stable against further change.
Knowing the rates of radioactive decay, and the relative quantities of radioactive and stable isotopes, one can estimate when the species were originally formed. Isotopes are nuclei that have the same chemical properties but differ one from another in their mass because of differences in their neutron content. For example, uranium 238 and uranium 235 are isotopes, both radioactive and each containing 92 protons but differing principally in that there are three fewer neutrons in uranium 235. That radioactive species exist at all suggests that either they were formed at a finite time in the past or else they are being created continuously in existing structures such as stars; both possibilities argue for an evolving universe.
At least three kinds of observations are regarded as strong evidence for the Big Bang model. First and most important are the famous observations by the astronomers Vest M. Slipper, Edwin P. Hubble, and Milton S. Human at Mount Wilson Observatory in the 1920 s and 1930 s.
They found that on a large scale, galaxies are observed to be receding from one another. Observers everywhere in the universe will see the same expansion effect. The word everywhere is significant, for it distinguishes the Big Bang from the simple and intuitive but irrelevant model of an explosion from a finite source. The correct physical picture is that galaxies and gravitationally bound clusters of galaxies are embedded in spacetime, which is itself expanding. Galaxies that are located in this matrix and are now farther away from any observer had to have been traveling at a higher speed away from the observer to arrive where they are now. Thus, there results the famous velocity-distance relation known as the Hubble law, in which the apparent recession velocity of galaxies is proportional to their distance from the observer.
The effect of expansion within, say, a local system such as the solar system, or even a galaxy or a cluster of galaxies, is overwhelmed by the larger gravitational attraction in local systems. In the more than 70 years since this result was first published, no acceptable alternative physical explanation has been developed for the reddening of the light. The shift toward longer wavelengths on which the Hubble law is based can be characterized as a Doppler shift arising from the expansion of space, and appearing to the observer as a motion of the emitter away from the observer. Again, we emphasize that in terms of general relativity, what is actually expanding is space, or the classical measuring rod that one uses to measure distances. A simple exploding bomb analogy is inapplicable because it is inherent in the model that although the cosmic expansion had an origin in time (it began at and indeed acted to define the zero of time), there was no preferred location in space for an infinite or unbounded universe, consistent with there being no preferred observers. Hence, the expansion occurred everywhere at a given time.
Discussion Although Einsteins Big Bang Theory does a very good job of explaining our universe, there have been many observations as of late that can more simply explain the creation of the universe. Many of Einsteins theories require complex mathematics to prove what can be simply explained by another phenomena. Ockham's razor shows that the simpler of two theories, that explain the same thing, is the more correct of the two. Some of the inherent faults in the big bang theory are its assumptions.
The first assumption is the uniform distribution of mass. Although on the widest view of space the mass appears to be distributed evenly throughout the universe, on any narrow view, it appears to be a fractal distribution. This problem carries over to the mass density of normal matter being about three percent of that of the critical density. If the mass isnt evenly distributed throughout the universe, the three percent density could not be accurate.
Another problem in the Big Bang Theory is the answer for red shift. Red shift is, according to the Big Bang Theory and General Relativity, just the Doppler effect on light. This cannot explain why our sun is slightly red-shifted when we arent moving towards or away from it. This red shift is accredited to the Compton affect of the photons traveling through a cloud of dust and stray electrons. As the photon travels through this debris, it loses energy and tends towards a shorter wavelength.
This is much simpler and better explained than the Doppler shift. This also causes a problem with quasar stars because they have been used as the oldest stars in the universe because of their red shift. If the Compton affect is used to explain this rather than Doppler shifting, it eliminates them as tools in judging the age of the universe. The Compton affect allows us to realize that quasars could exist all around the universe.
Conclusion Nevertheless, The big bang theory has its good points and its bad points. I dont believe that it is either right or wrong. There are already points to it that are being disputed such as the slowing rate of the expansion of the universe, but there are also points that may very likely never be disprove. One such point is Einsteins great equation E = mc 2. This equation has been worked into many different aspects of science from chemistry to astronomy and astrophysics. It is truly a work of art.
If the Big Bang Theory is ever, truly debunked, the theory to take its place will have an impact like no one has ever seen before. Bibliography: Peebles, P. et al. The Evolution of the Universe, Scientific American, 271, (1994): 29 - 33. Ben-Art, Yonatan. The Creation of the Universe & Black Holes, 1997 < web > Pearson, Ron.
New Theory on the Creation of the Universe. 2002 < web > Introduction to Cosmology. 2003 < web > Big Bang. 2004 < web > Big Bang Cosmology. 2005 < web >
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