1. Key Understanding 1.There are several theories regarding the creation of the universe. 1.Evidence gathered from the past is used to explain the universe and help predict the future. 1.Light years are units of time used to measure the distance between objects in the universe. A light year is based on the speed of light and is a measure of distance, not time. A light year represents how far light travels, through a vacuum, in one year. 1 light year is a measurement equal to 10 trillion km or the distance light travels in 1 yr.

2. Flat Earth Theory Ancients believe Earth is flat, not round! Greek philosopher Aristotle Flat Earth Theory died in the 16 th century. Aristotle believed the Earth was round because of Earth’s round-like shadow on the moon during a lunar eclipse. When a ship appears over the horizon, you should see the whole ship at the same time if the Earth was flat; instead you a see a little at a time.

3. Ptolemy Universe Theory Geocentric Model: Claudius Ptolemy (Greek astronomer) explains that Earth is at the center of the universe. This was the belief prior to the 16 th century, but had no proof. Remarkable mathematician for predicting the planet’s circular orbits at a constant speed, although this circular orbit is inaccurate. Problem: Could not explain planets’ changing speeds.

4. Copernicus Universe Theory Heliocentric Model: Nicolaus Copernicus (Polish astronomer and mathematician) explains that the sun is at the center of the universe. Theory proposed in the 16 th century, year 1500’s. Problem: still clung to the idea that the planets move in a circular orbit at constant speeds, although inaccurate. Direct Evidence Contributed Later: Newton’s laws of motion proved that the Earth revolved around the Sun. Newton states that lighter objects move more than heavier ones. Because the Sun has 330,000 times more mass than Earth, the Earth must be doing all of the moving instead of the Sun.

5. Galileo Galileo was a great defender of the heliocentric model. He was the first person who used a telescope to observe the sky. This was the first time that a person used an instrument to enhance one's observing capability. Galileo had four major discoveries: 1.The mountain terrain on the Moon. 2.The sunspots. 3.Four satellites orbiting around Jupiter, now called Jupiter’s Four Galilean moons. 4.Venus goes through a full set of phases, proving that it must orbit around the Sun as Earth does.

6. Kepler’s Universe Theory Johannes Kepler (German astronomer & mathematician) modified Copernicus’ heliocentric model in the 17 th century. Was able to explain the planets movement within the solar system. Credited for the Three Laws of Planetary Motion: (see animation link) http://www.astro.utoronto.ca/~zhu/ast210/kepler.html http://www.astro.utoronto.ca/~zhu/ast210/kepler.html 1.Planets’ orbit in an elliptical pattern (more oval-like) instead of a circular pattern. 2.Planets’ varying speeds were determined that planets travel faster when it comes closer to the Sun and moves slower when farther from the Sun. 3.Planets’ speed is related to its distance from the Sun in which planets closer to the Sun orbit faster and planets farther from the Sun orbit slower.

7. Big Bang Theory Description Most popular and accepted theory (1927) of how our universe was created and that other galaxies are moving away from our own at great speed, in all directions, as if they had all been propelled by an explosive force 20 billion years ago that allowed all of the universe’s known matter and energy, space and time, to exist within a fraction of a second. After that, the universe expanded as time passed and matter cooled; more diverse kinds of atoms began to form and condensed into stars and galaxies. The universe did not explode, but is continuing to expand where one day life would end. (see animation & video link) http://www.astro.ucla.edu/~wright/balloon0.ht ml http://www.astro.ucla.edu/~wright/balloon0.ht ml http://imgsrc.hubblesite.org/hu/db/videos/hs- 2003-27-b-low_quicktime.mov http://imgsrc.hubblesite.org/hu/db/videos/hs- 2003-27-b-low_quicktime.mov Creating the theory Georges Lemaitre (Belgian priest, early 1900’s) first suggested the universe began from a single atom. Albert Einstein (Jewish physicist, 1905) added theory of relativity: 1.Special Relativity. it is impossible to determine whether or not you are moving unless you can look at another object, and that the speed of light is always constant. 2.General Relativity: it is impossible to tell the difference between gravity and the force of inertia from a moving object, and that large objects cause outer space to bend. The larger the object, the further space bends. Edwin Hubble (American astronomer 1928) added observations of galaxies speeding away from us in all directions Arno Penzias and Robert Wilson (American radio astronomers, 1965) added discovery of cosmic microwave radiation Students may think there was a huge explosion, rather than rapid expansion, that began the solar system, galaxies, and the universe. Rapid expansion created the universe which contains billions of galaxies, and each galaxy contains billions of stars.

8. Strong Points of Theory: 1.Explains the expansion of the universe 2.Predicts correct abundance of hydrogen and helium as most common elements in universe 3.Accounts for cosmic background radiation that is present in the space Weak Points of Theory: 1.Does not explain why the temperature of the background radiation remains constant over the entire sky 2.Does not support that the universe appears almost flat.

9. Friedmann Universe Theory 1920’s, Alexander Friedmann, Russian physicist & mathematician. He believed that Albert Einstein's general theory of relativity required a theory of the universe in motion.Albert Einsteinrelativity Flat Universe: the universe expands forever, but the speed at which the galaxies separate will eventually stop. Closed Universe: The universe size is finite, has an expansion limit. The Big Bang’s momentum to expand the universe will slow down due to the center of the universe’s gravity until it collapses back into itself called the “Big Crunch.” Open Universe: The universe size is infinite. There is not enough matter to stop the universe from expanding forever. Galaxies will continue to separate from one another, and separate slower as time passes until all the stars go out and the universe becomes cold and dark.

11. Steady-State Universe Description 1948 by Hermann Bondi, Thomas, Gold, and Fred Hoyle Theory that the universe looks the same from every spot in it and at every time, therefore our universe did not have a beginning and will not have an end. Believed matter was continuously created out of nothing Theory began to wither in 1960’s with discovery of quasar galaxies (galaxy with black hole at center) and cosmic microwave radiation leftover from the Big Bang.

12. No Boundary Universe Theory Proposed by Stephen Hawking and Jim Hartle The universe is finite in size and has no boundary because it did not begin with a singularity.

13. Oscillating Universe By Richard Tolman, 1960’s. As the universe grows hotter and brighter until it implodes into a singularity to create the Big Bang where all of the matter will expand, then eventually stop and contract back into itself in the Big Crunch, followed by another Big Bang, then Big Crunch in a never ending cycle.

14. Inflationary Universe Theory 1980, Alan Guth, American physicist Before the Big Bang, all the matter started off with the same temperature. After the Big Bang, the universe went through an extraordinarily rapid expansion and continues into the Big Bang model. Theory unites the forces of gravity, electromagnetism, and weak and strong forces into one, which helped predict that the universe cooled after the Big Bang where space would have had an excess energy that counteracted gravity in order to drive inflation.

15. Anthropic Universe Why did we survive? The Perfect Universe: has to have a specific physical properties in order to produce life, if not stars and life would not exist (second from top). If expands too quickly (top): matter would spread out too quickly to condense into stars, etc. If expands too slowly (bottom three): universe would collapse into “Big Crunch” already and we would not exist.

16. 1.Theories are the most accepted explanation, based on information from research. 2. The Big Bang Theory is based on observation that other galaxies are moving away from our Milky Way galaxy at great speeds in all directions. 3.Scientists believe that the universe is expanding because it’s based on the idea that galaxies are moving away from us. 4. Scientists revise their theories when the evidence supports the change.