Earth - an island in space
• Solar System
­ Sun and nine planets

• Galaxies
­ Groups of stars

• The Universe

• When and How did it all form????
Origin of the Universe
“ The Big Bang”
 => 14-20 billion years ago the universe began during a cataclysmic release of energy from a point source  of infinite mass.

- 10-43second -> matter/antimatter
-  quark soup - inflation

- 3000 bill degrees K - hadrons
- 3 minutes - dueterium & He nucleii

-  300k - H & He - photons released = light
-  first galaxies (~ 1 bill. Yrs.)

-  continued expansion

What is the evidence for this?
• An Expanding Universe

• Cosmic Background Radiation
How do we know the universe is expanding?
• Expansion is suggested by the “Red Shift” (Hubble, 1929)

• Red shift can be explained by the Doppler Effect

Evolution of Stars - Element Factories
• Stars begin as clouds of dust & gas = Nebula

• Gravity -- protostar

• High pressure and temperatures
­ H atoms fuse together to form He = fusion

• As stars run out of fuel
­ Become larger & explode
­ Supernova -> forms another nebula

• Begins to create heavier elements
­ He - C - N - O, ect.

Origin of the Solar System => Nebular Hypothesis
 
a) ~5 bill. yrs. ago - solar system began as large, slowly
rotating cloud of dust and gas - Solar Nebula

    => material from a supernova
b) Cooling and Gravity => from cloud to sphere.

c) Velocity of rotation increases => sphere to disk.

d) Most of mass near center of disk => proto-sun.
 

=> Sun turns on -  H + H = He -> nuclear fusion

e)  Planets form by chemical condensation/accretion.

  Evidence

1)  planets orbit in same plane

2) planets rotate in same direction as they revolve around the sun

3) Terrestrial versus Jovian planets

4) young stars observed surrounded by flattened disks of gas and dust

ORIGIN OF EARTH

a. Origin=> 4.6 b.y. ago => condensation/accretion
 
b. Earth heats up

c. Density Differentiation