Chapter 2 Outline

Chapter 2 Outline - Chapter 2: Solar Energy to Earth and...

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Chapter 2: Solar Energy to Earth and the Seasons Introduction Universe has bils galaxies; incoming solar energy tht goes Earth’s atmosphere=>pattern of energy input that drives Earth’s phys sys’s; this + Earth’s tilt/rotation causes daily, annual, seasonal patterns of changing daylength/Sun angle; Sun= ultimate energy source for most life in our biosphere The Solar System, Sun, and Earth Our solar sys located on remote edge of Milky Way Galaxy - flattened, disk-shaped mass w/~400 bil stars; is ½way+ out fr galactic center in Milky Way’s spiral Orion Arm ; huge black hole- Sagittarius A*- sits in center Solar System Formation and Structure Our solar sys condensed fr lg, slowly rotating/collapsing nebula ; gravity - mutual attracting force exerted by mass of object on othr objects- key force; as nebular cloud org’d into disk shape, early protosun grew in mass at center, drawing more matter to it; also Protoplanets - sml accumulations Starts of Sun, Solar Sys (SS) occurred 4.6+ bil yrs ago; early protoplants- planetesimals - orbited ~same distances fr Sun as modern planets; planetesimal hypothesis (dust-cloud hyp)- says how suns condense fr nebular clouds w/planetesimals forming in orbits about central mass Dimensions and Distances Speed of light = 300K km/s; light-year - great distance, 9.5 tril km, light travels in yr; measurement unit for Universe; known Universe seen fr Earth ~12 bil light-yrs in all directions; MW 100K L-yrs long; our Solar Sys ~11 hrs in diameter, as measured by L-yr speed Earth’s Orbit Earth’s orbit around Sun elliptical ; its avg distance fr Sun 150 mil km; Earth is at perihelion - closest position to Sun- in N Hemisphere winter (Jan 3); is at aphelion (farthest fr Sun) during N Hem summer; this seasonal diff causes slight variation ini solar energy coming to earth Plane of the elliptic - plane touching all pts of Earth’s orbit; earth’s tilted axis stays fixed relative to this plane as earth revolves round Sun; this plane impt to Earth seasons; structure of Earth’s orbit changes over long pers; diff’g distance fr sun 1 of svrl factors tht create Earth’s cyclical pattern of glaciations (colder)/interglacial (warmer) pers Solar Energy: From Sun to Earth Sun captured ~99.9% of the matter fr rig solar nebula; rest 0.1% formed the planets, thr satellites, asteroids, comets, debris; thus Sun dominant object in our reg of space; only thing in Solar Sys having enough mass/interior density/pressure to sustain nuclear rxns/produce radiant energy: Sun’s H atoms fuel together in fusion reactions- H nuclei form He, releasing huge qtys energy Solar Activity and Solar Wind Sun constantly emits clouds of electrically charged particles (H nuclei, free electrons)- travels slower than light- this= solar wind ; extends fr Sun past Pluto’s orbit; sunspots due to magnetic storms on Sun- diameter ranges 10K 50K km, bigger than Earth’s; they produce flares, prominences
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Chapter 2 Outline - Chapter 2: Solar Energy to Earth and...

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