Origins of the Earth, Oceans, and Life Unit 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

Stars & Galaxies Galaxies Stars huge rotating aggregations of stars, dust, and gas held together by gravity. Probably 50 billion galaxies with 50 billion stars in each Our galaxies 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

Stars cont. Condensation Theory- how stars and planets were formed Stars form in a nubula (cloud of cold dust and gas within a galaxy) 1. The nubula 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.

Formation of Solar System Earth and ocean are an indirect result of a supernova explosion (solar nubula) A solar nubula is like a spinning skater that brings their arms in. 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 & 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

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 form 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 million years old of bacteria-like organisms

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 form UV Material that accreted had minerals and water to form the Earth’s crust

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