The Big Bang Theory

1. The Big Bang Theory Elizabeth Walsh

2. A Static Universe • In the early 1900s, the accepted view held was that the universe was static, which never changes; it has always been the same and always will • Albert Einstein was one of the largest supporters of this belief • When the idea of an expanding universe was proposed, Einstein spoke out: “This circumstance irritates me. To admit such possibilities seems senseless.”

3. Hubble’s Discoveries • However, not everyone was convinced that the universe was never changing • In 1929, astronomer Edwin Hubble, at the Mt. Wilson Observatory in California, found that the velocity of a star appeared to be proportional to its distance from the Earth • The further the star from the Earth, the faster it appeared to move away from the Earth • This concluded that the universe is expanding and the galaxies are moving away at high speeds

4. Einstein’s Mistake • Looking to gain a greater understanding of the universe, Einstein turned to his theory of general relativity- the current description of gravitation in physics • His surprising discovery found that the universe would have to be expanding and contracting • Hubble’s findings, paired with Einstein’s theory supported the idea of an expanding universe

5. Georges Lemaitre • Georges Lemaitre was a Belgian Cosmologist and Catholic priest • Used Einstein’s laws of gravitation as a basis to claim that the universe must be expanding • He published a solution to equations of general relativity in 1927 in regards to the expanding universe • Stated that the expanding universe was not static – but without evidence he had little support • His model soon became known as the “Big Bang Theory”

6. The Big Bang Theory • Combination of two approaches to the universe: astronomical and cosmological • Describes the development of the universe prior to its current existence • All matter and space in the universe was originally compressed into a tiny dot, called the singularity, which expanded and all the matter instantly filled what is now our universe

7. Evidence for the Big Bang • Lemaitre used Hubble’s findings to support his theory • If the galaxies are currently moving forward, at one point they must have been all together • Once there was a primordial atom that contained all the matter in the universe • Lemaitre also used the concept of entropy - everything is moving towards greater disorder – to support his theory

8. Following the Discovery • Much debate followed his theory - some supported the idea while others chose to take on a “steady state” theory • The universe is constantly expanding, but the average density remains constant • Debate ended when Arno Penzias and Robert Wilson found evidence for cosmic background radiation – residue of the big bang • The expansion of the universe is now viewed as one of the greatest scientific discoveries

9. Impact of the Big Bang Theory • The Big Bang Theory sparked discussion and encouraged further studied into the universe • This theory is used as a way to estimate the age of the universe (within a large range) • It also lead to questions relating to the universe expansion – Will it expand forever? What happened before the big bang?

10. “Never in all the history of science has there been a period when new theories and hypotheses arose, flourished, and were abandoned in so quick succession as in the last fifteen or twenty years.” • Willem de Sitter, 1931

11. References • Big Bang Theory is Introduced. (n.d.). PBS. Retrieved February 26, 2014, from http://www.pbs.org/wgbh/aso/databank/entries/dp27bi.html • Georges Lemaitre, Father of the Big Bang. (n.d.). Georges Lemaitre, Father of the Big Bang. Retrieved February 26, 2014, from http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_lemaitre.html • Strickland, J. (2008, June 18). How the Big Bang Theory Works. HowStuffWorks. Retrieved February 25, 2014, from http://science.howstuffworks.com/dictionary/astronomy-terms/big-bang-theory.htm • The Expanding Universe (Cosmology: Ideas). (n.d.). The Expanding Universe (Cosmology: Ideas). Retrieved February 26, 2014, from http://www.aip.org/history/cosmology/ideas/expanding.htm