Unit 2

1. Origins of the Earth, Oceans, and Life Unit 2

2. Big Bang Theory • Universe had a beginning • Occurred 15 billion years ago • Started the expansion of the universe from a geometric point. • Expansion continues today • A billion years later the stars and planets congealed

3. Stars & Galaxies • Galaxies • huge rotating aggregations of stars, dust, and gas held together by gravity. • Probably 50 billion galaxies with 50 billion stars in each • Our galaxy is the spiraled Milky Way • Galaxies can be elliptical, irregular, and spiral • Stars • massive spheres of incandescent gas • There are more stars in the Milky Way than grains of sands on all beaches • The sun is a typical star

4. Stars cont. • Condensation Theory- how stars and planets were formed • Stars form in a nebula (cloud of cold dust and gas within a galaxy) 1. The nebula shrinks under its own weak gravity 2. Increases the temp and nuclear fusion turns H He 3. Liberates energy (this is why stars shine) 4. Stops shrinkage and stars become somewhat stable 5. As star converts more H into heavier elements the energy output rises and the body of the star swells into a “red giant” 6. Star’s core will eventually collapse in an explosion (star blows up)- supernova • Every chemical element that made the planets, stars, oceans, and organisms is made up of star dust.

5. Formation of Solar System • Inner material concentrated into a protosun and outer material formed outer planets • Planets formed through accretion - clumping smaller particles into larger masses. • Accretion period lasted 50-70 million years • Earth and ocean are an indirect result of a supernova explosion (solar nebula) • A solar nebula is like a spinning skater that brings their arms in.

6. Earth & Ocean • Earth was heated by kinetic energy of falling debris and decay of radioactive elements within the newly formed Earth, causing it to melt • density stratification - Iron sunk to the middle of the planet (developing gravity field), and lighter minerals (Si, Al, Mg) migrated to the surface forming the Earth’s crust • At 4.6 bil years, first surface formed • Outgassing (release of volatile substances and water vapor) occurred everywhere and caused massive clouds in upper atmosphere • No liquid water was on the Earth, intense lightening occurred, and sunlight couldn’t penetrate the clouds surrounding the Earth. • Eventually, clouds cooled and formed water droplets that fell to the Earth, but boiled back into the clouds once they touched the Earth • Once the surface of the Earth cooled, water collected in basins and also dissolved minerals from rocks. • Heavy rains fell for 10 million years to eventually form the oceans • Early atmosphere included methane, ammonia, carbon dioxide, water vapor, and other gases

7. Origins of Life • Stanely Miller’s experiment in 1953 • Mixed the early atmosphere gases in a closed container with a spark • In a short time amino acids, small proteins, and nucleotides formed. • Life did not form from Miller’s experiment, but the building blocks of life did • All life needs water and saline (for cells) • therefore it is widely accepted that life arose somewhere in the early ocean • Early steps of organisms forming from organic building blocks is called biosynthesis • Evaporation of water, concentration of amino acids and nucleotides could be formed in a rich organic soup • John Corliss suggests that heat energy from thermal vents in the sea (high concentrations of minerals) could have formed into complex molecules of life • Oldest fossils are 3.4-3.5 Billion years old of bacteria-like organisms

8. Ocean World • Reasons why the Earth is ideal: • Distance from sun allows for liquid water • Temp just right because of sun • Gravity force is just right • Single moon provide for gentle tides • Atmosphere clear so sun can penetrate • Ozone layer protects us from UV • Material that accreted had minerals and water to form the Earth’s crust

9. Future of Earth • 6 billion years from now, the sun (as a red giant) will probably engulf the inner planets and burst.

10. “How We Know…” • Edwin Hubble – made discovery that distant stars and galaxies are receding from the Earth in all directions. This implies that the universe is still expanding. • Planetsimals are aggregations of gas and dust which may be several hundred kilometers in diameter. Earth is believed to have been formed by aggregations of planetsimals. • Zircon crystals found in Australia are the oldest rocks. They are 4.3 billion years old. Scientists cannot measure the age of the Earth by measuring the oldest rocks because those rocks were probably “recycled”. The Earth’s oldest rocks are found on all the continents. Some include 4.030 billion years old in Canada and 3.7-3.8 billion years old in Greenland. • The moon has a tiny metallic core because it is believed it broke off from the earth when it was hit by a meteoroid when it was about half formed.