1. Theories of how the Universe Began
Beginning With a Bang

2. Big Bang Theory
Scientists believe Universe started with a big explosion
15 billion years ago
Matter, gravity, and electromagnetism were created by the blast
Universe expanded

3. Edwin Hubble First to discover Universe expanding
Distant galaxies moving away from Earth faster than close ones
Discovery of cosmic background radiation supported Hubble’s theory
Four basic forces control the Universe: gravity, electromagnetism, strong nuclear forces, weak nuclear forces

4. Hubble Cont. As Universe expanded, it began to cool
One billionth years old, started condensing into galaxies, stars and planets

5. Oscillating (Big Squeeze Theory)
Expansion of the Universe (Big Bang) will be followed by a contraction or a squeezing of the Universe
This is caused by gravity
Farther planets will slow down and stop, then fall toward the center
Planets will collide
A new Big Bang will occur

6. Steady State Theory Challenged Big Bang Theory in 1940
Scientists believe that Universe did not begin with an explosion
Believe Universe will exist forever (steady state)
Theory discarded after discovery of cosmic background radiation

7. Today
Scientist believe a fraction of a second after Big Bang explosion, gravity emerged
At birth, Universe was 180 billion degrees Fahrenheit
60 seconds later it cooled to 18 billion degrees Fahrenheit
Today average temperature of Universe is degrees Fahrenheit

8. Measuring Vast Universe
Basic unit of distance: light year
Light year – the distance light travels in one year or about 6 trillion miles.