2. The Big Bang Theory Elizabeth Walsh

3. 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.”

4. 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

5. 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

6. 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”

7. 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

8. 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

9. 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

10. 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?

11. “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

12. References Big Bang Theory is Introduced. (n.d.). PBS. Retrieved February 26, 2014, from http://www.pbs.org/wgbh/aso/databank/entries/dp27bi.htmlhttp://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 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 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 http://www.aip.org/history/cosmology/ideas/expanding.htm