Friday, September 19, 2008

The Cosmic Microwave Background


The Cosmic Microwave Background

After some period of time following the big bang, gravity condensed clumps of matter together. The clumps were gravitationally pulled towards other clumps and eventually formed galaxies. It is extremely difficult to model how this clumping may have occurred, but most models agree that it occurred faster than it should have. A possible explanation is that right after the big bang the Universe began a period of exaggerated outward expansion, with particles flying outward faster than the current speed of light. This explanation is known as inflation theory, and has widespread advocacy within the astrophysics community because it reconciles theory with observation. It should be noted, however, that inflation theory is not directly verifiable.

Big Bang Theory - Evidence for the Theory

Big Bang Theory - Evidence for the Theory
What are the major evidences which support the Big Bang theory?

  • First of all, we are reasonably certain that the universe had a beginning.
  • Second, galaxies appear to be moving away from us at speeds proportional to their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.
  • Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.
  • Finally, the abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins. 

 

Big Bang Theory - Common Misconceptions

Big Bang Theory - Common Misconceptions
There are many misconceptions surrounding the Big Bang theory. For example, we tend to imagine a giant explosion. Experts however say that there was no explosion; there was (and continues to be) an expansion. Rather than imagining a balloon popping and releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe.
Another misconception is that we tend to image the singularity as a little fireball appearing somewhere in space. According to the many experts however, space didn't exist prior to the Big Bang. Back in the late '60s and early '70s, when men first walked upon the moon, "three British astrophysicists, Steven Hawking, George Ellis, and Roger Penrose turned their attention to the Theory of Relativity and its implications regarding our notions of time. In 1968 and 1970, they published papers in which they extended Einstein's Theory of General Relativity to include measurements of time and space. According to their calculations, time and space had a finite beginning that corresponded to the origin of matter and energy. The singularity didn't appear in space; rather, space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy - nothing. So where and in what did the singularity appear if not in space? We don't know. We don't know where it came from, why it's here, or even where it is. All we really know is that we are inside of it and at one time it didn't exist and neither did we.