Exam 1 Study Guide Cosmology 1000 BC earth was flat stars overhead in celestial field 200 BC Eratosthenes calculated circumference of earth 330 BC Heraclides formed first solar system model geocentric 270 BC Aristarchus develops heliocentric theory o Around the earth o Around the sun 150 AD Ptolemy believed in a geocentric universe with circular orbits but couldn t explain retrograde motion o Loop in orbit 1500 Copernicus develops new heliocentric model with circular orbit 1600 Keppler says planets have elliptical orbit 1600 Galileo confirms heliocentric model with telescope Galaxy Immense system of stars pulled together by gravity Solar System collection of planets revolving around a star Do galaxies move in relation to each other Doppler Effect Different pitches are heard at different distances Use prism to split rays of light while looking at a star or planet through a telescope to determine distance Hubble mostly saw red or long wavelengths moving away o Red shift moving away o Blue Shift moving closer o Concluded that universe must be expanding Origin of the Universe All matter and energy is compressed to single point that is infinitely dense Within 1 second the Big Bang occurred 13 7 billion years ago where the point exploded o The universe expanded and cooled enough to allow protons and neutrons and H to form o After 3 minutes H He and Li formed Soon after elements began to cool and collected into clouds called Nebulas o Gravity shifted and expanded some nebulas o Larger nebula cores become more dense due to gravity H and He collide fusion and form more complex elements up to Fe Byproduct is light Energy is released and a star is born o When all H and He is used up the star becomes a supernova and explodes Scatters all mass across space forming the rest of the 92 elements Nebular Hypothesis formation of our solar system o Fusion and the explosion of a supernova created a new nebula consisting of all the elements The nebula condensed into a swirling disc called an accretionary disk o Separation of Sun and planets Center becomes hot and dense fusion begins and sun forms Dust particles condense into rings around sun Dust particles collide and stick to become planetesimals Formation of Earth o Planetesimals grew by multiple collisions o Center became heated and became soft o Gravity reshaped into sphere o Homogeneous Earth Formed from multiple impacts of materials left over from the Big Bang fusion reactions and supernova explosions Earth began to differentiate elements based on density Heaviest stuff lies in center o Heterogeneous Earth Differentiates into layers Outer core liquid Fe Inner core solid Fe Formation of Moon o Small planet collided with earth after being formed Collision blasted debris into ring that orbited Earth Moon formed out of this ring of debris o Time was similar to formation of earth Formation of Oceans and Atmosphere oceans Size and Position of Planets o Atmosphere developed from gases coming from volcanoes o Earth cooled enough moisture condensed into atmosphere to form rain that created o Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune o Sun is infinitely greater in size and density than earth o Terrestrial Planets Closest to sun Mercury to Mars Dense rocky planets formed 4 7 billion years ago Light gases blown away by solar winds leaving heavy minerals o Gas Giants or Jovian Planets Jupiter to Neptune Far enough away from sun to keep gas material Farthest from sun Small rocky cores Mostly H and He and other light elements commonly creating ice Elemental Composition of Earth Mostly iron in the core 35 Iron 30 Oxygen 15 Silicon 10 Magnesium 10 other Found in organic compounds minerals glass rocks metals melts or gas Only ever sampled 18 of earth s interior by going down 12km Occasionally volcanoes bring up pieces of mantle xenoliths Crust 40km Upper Mantle 600km Lower Mantle 2241km Outer Core 2359km Inner Core 1220km Total of 6378km Radius Silica tetrahedral link together to make most common minerals SiO2 Silicates How to sample the earth s interior Use gravitational pull of objects to determine density of objects Earths density 5 5g cm3 Surface rock density 2 5 3 0 g cm3 Use densities to determine the arrangement of minerals Seismic Waves o Fault deep seeded fracture of earth s surface o Movement along fault creates waves P or S waves o Changes in velocity of waves show differences in densities of material in earth s core Dr Inge Lehmann used seismic waves to discover the earth s inner core Geothermal gradient o Temperature rises as density increases Lithosphere rigid brittle non flowable outer 100 150 km crust and top of mantle o Moho separates crust and mantle Asthenosphere soft ductile flowable between 150 350km Mantle largest part of the earth by volume solid but partially melted Core composed of liquid iron outer solid iron inner Other Facts about Earth Has magnetic inclination o Magnetic field reverses after time