1. Theories of the Origins of the Universe

2. Geocentric Theory When was the theory developed and when was it eventually published? Between 140 – 150 AD Who developed the Geocentric Universe theory? Claudius Ptolemaeus (Ptolemy) What does the theory says about the origin of the universe? Earth is the center of the universe Where is the astronomer from? Ancient Greece

3. Geocentric Theory How was this theory developed? Who later expanded his model, and who made observations that backed up this theory? They observed the stars, sun, and planets revolving around Earth. From this, they assumed that the Earth was motionless and all other objects they could see were moving around the Earth. This is understandable because they could not feel the Earth itself moving but could see the stars moving around it.

4. Heliocentric Universe When was the theory developed and when was it eventually published? 1512, not published until 1543 Who developed the Heliocentric Universe theory? Nicolas Copernicus What does the theory says about the origin of the universe? The sun is the center of the Universe. Where is the astronomer from? Poland

5. Heliocentric Universe How was this theory developed? Who later expanded his model, and who made observations that backed up this theory? Copernicus created a mathematical model to prove his theory. Kepler expaned this model and Galileo later made supporting observations with a telescope.

6. Friedman’s Universe When was the theory developed and when was it eventually published? Early 1920’s Who developed the Friedman’s Universe theory? Alexander Friedman What does the theory says about the origin of the universe? “The Friedman universe begins with a Big Bang and continues expanding for untold billions of years (that’s the stage we’re in now.) But after a long enough period of time, the mutual gravitational attraction of all the matter slows the expansion to a stop.” The universe will eventually start to contract in a big crunch. Where is the astronomer from? Russia

7. Friedman’s Universe How was this theory developed? Who later expanded his model, and who made observations that backed up this theory? Friedman embraced the idea that the equation in Einstein’s theory of relativity shows a universe that is in motion, and not constant.

8. The Big Bang Theory When was the theory developed and when was it eventually published? 1926 Who developed the Big Bang Universe theory? Georges Lemaitre in 1926; Edwin Hubble contributed in 1929 What does the theory says about the origin of the universe? 15 billion years ago all matter in the universe was contained in a single point. A huge explosion occurred that sent matter flying in all directions. Where is the astronomer from? Marshfield, Missouri USA

9. The Big Bang Theory How was this theory developed? Who later expanded his model, and who made observations that backed up this theory? Hubble noticed that all of the objects he observed had a red shift, which meant they were moving away from each other. Red shift- If an object is moving away it’s light is shifted to longer wavelengths and looks red.

10. The Steady State Theory When was the theory developed and when was it eventually published? 1948 Who developed the Steady State Universe theory? Herman Bondi, Thomas Gold, &Fred Hoyle What does the theory says about the origin of the universe? It proposes that matter is being continuously created at the rate of a few hundred atoms per year. This would allow the density of the universe to remain constant as it expands. Where are the astronomers from? Fred Hoyle- England Thomas Gold – Austria Hermann Bondi - Austria

11. The Steady State Theory How was this theory developed? Who later expanded his model, and who made observations that backed up this theory? Hoyle says that the universe looks the same at all times, therefore, if it is expanding, then new matter must also be created. The discovery of quasars, the cores of distant galaxies, led to the disproval of this theory. Their existence proves that the ancient universe is not the same as the younger universe.

12. Oscillating Universe Who developed the Steady State Universe theory? Alexander Friedmann (1922), Albert Einstein (1931), and Richard Tolman, (1932) When was the theory developed and when was it eventually published? 1920’s to 1930’s Where is the astronomer from? Alexander Freidman – Russia Albert Einstein – Germany; became US citizen in 1940 Richard Tolman – Massachusetts

13. Oscillating Universe What does the theory says about the origin of the universe? The oscillating universe theory believes that the universe began in a giant explosion and is expanding (The Big Bang Theory). It states that the universe will continue to expand until all energy is used up and will then collapse on itself until it comes together in a big “crunch” (Friedmann’s Theory). In the oscillating universe theory, this cycle would continue indefinitely.