Age Of The Universe Essay Research Paper — страница 2

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contains. Such estimates typically yield ages in the range 14-18 billion years Hubble Time The inverse of the Hubble constant H has the units of time because the Hubble law is v = H d where v is the velocity of recession, H is the Hubble constant, and d is the distance. Thus, from this equation, we have that 1/H = d/v. but d/v is distance divided by velocity, which is time (e.g., if I travel 180 miles at 60 miles/hour, the time required is t = d/v = 180/60 = 3 hours). Thus, the Hubble time T is just the inverse of the Hubble Constant: T = 1 / H Taking a value of H = 20 km/s/Mly (where Mly means mega-light years), where all the factors are necessary to convert the time units to years (Cowen, 1994). The physical interpretation of the Hubble time is that it gives the time for the

Universe to run backwards to the Big Bang if the expansion rate (the Hubble “constant”) were constant. Thus, it is a measure of the age of the Universe. The Hubble “constant” actually isn’t constant, so the Hubble time is really only a rough estimate of the age of the Universe. Reasonable assumptions for the value of the Hubble constant and the expansion of the Universe typically yield ages of 10-20 billion years for the age of the Universe. For example, H near 50 km/s/Mpc gives a larger value for the age of the Universe (around 16 thousand million years), while a larger value of 80 m/s/Mpc gives a lower value for the age (around 10 thousand million years). Therefore, we shall take this information, and additional information from other methods to estimate the age of

the Universe that we have not discussed, to indicate an age of approximately 15 billion years for the Universe. ASSUMPTIONS: With the large difference in the time of the 3 different formulas, we are assuming that at the time of the big bang there were equal amounts of U238 and U235. Through the natural rate of decay, we are taking the assumption that there was no immigration of any U235 or U238 into the universe that was not there are the time of the big bang. With the possible addition or subtraction of U235 and U238 through a supernova, this could possibly skew the ratios of U235 and U238 today. David Thorsell of Seattle University states that assuming that at the time of the big bang there were equal amounts of U235 and U238 is a very large leap of faith and that the case is

probably not true. Also he states that two isotopes radioactivity differ from each other due to the difference in their nuclei. Thorsell explains that the sample of the isotopes have only been taken from earth, which is not a true representation of the rest of the universe. The Fate of the Universe The Universe is currently expanding. One extremely important cosmological question is whether this expansion will continue forever. As time will tell, this is a question that does not yet have a definitive answer. Ultimately, this will turn out to be a question of how much mass is contained in the Universe (Cowen, 1995). If it is below a critical amount, the Universe will expand forever. If it is above the critical amount, the expansion will eventually reverse and the Universe will

collapse on itself, leading to what has been termed the big crunch. If it is exactly equal to the critical amount, the expansion will slow, but will only stop after an infinite amount of time. Thus, in this case the Universe will expand forever too. Is the Universe Really That Old? Many creationists believe that the universe was, well created and that the universe is only roughly a few thousand years old. They use the following facts to discredit the notion of an old universe. “Our sun is gradually shrinking at a steady rate. It is occurring fast enough that, as little as 50,000 years ago, the sun would have been so large that our oceans would boil. In far less time in the past (25,000 years or so), all life on earth would have ceased to exist”. “Computer simulations of the

motions of spiral galaxies show them to be highly unstable; they should completely change their shape in only a small fraction of the assumed evolutionary age of the universe. The simplest explanation for the existence of so many spiral galaxies, including our own Milky Way Galaxy, is that they and the universe are much younger than has been assumed.” It seems as though there is scientific data everywhere to prove and disprove any theory. One theory that I would like to ponder is the “Big Bang”; the foundation of the “Big Bang” is that nothing imploded from nothing and the outcome was the universe. Scientist would have to believe this as truth and accept nothing else or try to prove something different. It resembles believing in God, people are convinced that God is God