1Earth Science 104Earth’s Place in the Cosmos, StructureHistory of AstronomyScales of Space and TimePlanet EarthAtmosphere Biospherehttp://www.earthscienceeducation.com/creative_science/chemistry_index.htmGeospherehttp://www.miamisci.org/ecolinks/geosphere.htmlSphere interactionsComplex Interactionshttp://www.msu.edu/~colungag/docs/philosophy.htmHydrologic Cyclehttp://www.mnforsustain.org/water_climate_global_water_cycle_study.htm2Internal and external cycles Crusthttp://earthquake.usgs.gov/learning/glossary.php?term=crustTectonic movementsTectonic Plates ConvectionEarth’s Structure• Rocky Planet– Silicates– Metals• Melting allowed gravity to separate by density– Metals drawn to center– Silicates dominate the remainder• Oxygen and Silicon most common elements• Combine with other elements to make feldspars, pyroxenes, amphiboles and quartzComposition• Core ~ 3500 km radius• Mantle ~ 2900 km thick• Crust < 100 kmEarth’s Interior Properties• Inner core: solid• Outer core: liquid• Lower mantle: fairly solidEarth’s Interior Properties• Inner core: solid• Outer core: liquid• Lower mantle: fairly solid• Asthenosphere• Lithosphere3Internal Division• Mantle-Crust boundary is compositional– More silica, less iron, magnesium in crust than mantle• Asthenosphere-Lithosphere boundary is based on properties– Asthenosphere is weak, flows– Lithosphere is rigid and contains some of the upper mantle, and all of the crustInterface of spheres Nebular Hypothesis• NEBULA—Rotating cloud of dust and gases • Our solar system–Sun– Major Planets– Dwarf planets, asteroids and comets• Hypothesis that it formed from nebula by gravitational contraction and solids colliding and becoming planets, etc. Solar system formed from nebular cloud • Occurred about 5 billion years agoBig Bang forms all matter• Much more ancient than nebular collapse• “Beginning of the universe” about 14 b.y.a.Was the ‘big bang’ the event that formed our solar system? No! The ‘big bang’ was the singularity that created the matter and space of the universe. It occurred about 9 billion years before our solar system condensed from a nebula. What is a nebula?a swirling cloud of dust and gasesHistory of Astronomy• Ancient civilizations believed that Earth was at the center of the universe—GEOCENTRIC MODEL• Age of Reason beginning to recognize Sun is center of Solar System—HELIOCENTRIC MODEL• Age of Technology exploring wide reaches of the universeAnaxagoras•5thcentury B.C.• Moon is a sphere lighted by Sunhttp://www-history.mcs.st-andrews.ac.uk/Biographies/Anaxagoras.htmlAristotle•4thcentury BC• Earth is a spherehttp://www.hao.ucar.edu/public/education/sp/images/aristotle.html4•3rdcentury BC• Mathemetician• Placed Sun at center with Earth orbiting itAristarchus of SamosEratosthenes calculatedEarth’s size in ~ 240 BChttp://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_the_EarthPtolemy•2ndcentury AD• Copies of works survive to this day• Translated to Arabic early, to Latin in 13thcenturyPtolemy’s map of Europehttp://archive.ncsa.uiuc.edu/SDG/Experimental/vatican.exhibit/exhibit/full-images/d-mathematics/math21.gifPtolemy’s Solar SystemEpicycle explains retrograde motion• Since thought was Earth is the centerRetrograde motion• Mars usually moves across sky west to east• Occasionally appears to move east to west• Occurs when Earth is ‘passing’ MarsPtolemy’s work• Translated into Latin in 13thcentury• Influenced intellectual thought for centuriesArguments against Heliocentric Model• Earth would fly apart if it rotated on an axis• Moon would be left behind if Earth orbited Sun• Since God created Earth and Sun and all the heavenly bodies, Earth is the center of the
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