Professor Marie McCrary
PHY 111 - Astronomy
5 May 2014
Big Bang Theory Ever since the humans have formed life on earth, there has been ongoing questions about how everything was started at one point. The creation of our universe was not fully proven by any theory that existed, until the Big Bang Theory. The Big Bang Theory is one of the most reliable and widely accepted theories for the origin and evolution of our universe.
The theory was originally discovered by a Belgian priest and scientist, Georges Lemaitre in
1920's. As of today, the Big Bang Theory has been supported by many scientists around the world to solve the greatest mystery left for human kind, the origin of the universe. According to the Big Bang Theory our universe had formed about 12 to 14 billion years ago by a massive explosion. Before the big bang, our universe was at an unbelievably tiny (few millimeters across), bright, hot and high dense stage, and after this massive blast the universe expanded at a trillion-trillionth of a second. Big Bang supporters believe that as the universe expands in incredibly fast rate, temperature and density dropped drastically over time. Through this process, more diverse types of atoms had formed and they began to combine into stars and galaxies that have been come to known as our present universe. In
1917 a famous physicist Albert Einstein, established the general theory of relativity which insisted that our universe neither expands nor contracts. But soon after an American astronomer Edwin Hubble's founded Hubble's Law, Einstein admitted his mistake in 1929. According to N.C.S.A (National Center for Supercomputing Applications) a unit of University of Illinois at Urbana-Champaign, they state that
Hubble, who had been the first to establish that the universe included many other galaxies outside of our own, noticed something else: the galaxies were receding from us at a velocity proportional to their distance. The more distant the galaxy, the greater its redshift, and therefore the higher the velocity, a relation known as Hubble's Law. The velocity v could be determined by multiplying the distance R by H, the Hubble constant, given by the slope of the line in the above graph, in units of kilometers per second per million light years. The Hubble constant describes the universe's rate of expansion. (NCSA)
This simply means that V=H•R. Hubble's law is one of the major strengths that supports the Big Bang Theory, if our universe is continuously expanding after the big bang it is likely to say that we can possibly estimate the time it would take our universe to contract from its beginning, the big bang. On the contrary, this theory leaves one fundamental matter unanswered, 'The cause of the big bang itself'. The theory reasonably explains the origin of our universe few seconds after its formation but it does not answer what happened before those few seconds. (after this massive blast the universe expanded at a trillion-trillionth of a second, P1) The Cosmic Inflation Theory was introduced in 1980s by American physicist Alan
Guth to support early stages of the classical Big Bang Theory. This theory suggests that our universe has drastically expanded after the big bang compared to how we experience inflation.
Moreover, if we divide the space into large scales of hundreds of million light years, and not one planet to another, its average characters like mass density, galaxy density, and light output closely resembles the other. Also, the COBE mission has proved that the cosmic background radiation of our universe seems uniformed which is at 2.7 K. From the uniformity of the universe, scientists infer that once our universe was at a tiny stage. Alan Guth stated that Because the region was so small, there was plenty of time for it to come to a uniform temperature, by the same mundane processes by which a cup of hot coffee cools to room
