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Unformatted text preview: Chapter 2 Solar Energy, Seasons, and the Atmosphere The Solar System, Sun, and Earth Solar Energy: From Sun to Earth The Seasons Milky Way Galaxy Our solar system located on trailing edge of Milky Way Galaxy Disk-shaped mass of nearly 400 billion stars Nebular/Planetisimal/Dust-Cloud Hypothesis Solar system condensed from a large, slowly rotating cloud of dust and gas, a nebula The force of gravity caused dust and gas particles to condense into suns and planets Planets accumulated additional dust, gases and icy comets Formation of Sun and its solar system dates to 4.6 billion years ago Solar System Formation and Structure Gravity Mutual attracting force exerted by mass on all other objects Planetesimal hypothesis Suns condense from nebular clouds Speed of Light 299,792 kmps (186,282 mps) ca. 186,000 Light-year = distance that light travels in a year = 6 trillion miles Known universe is 12 billion light-years across Milky Way Galaxy 100,000 ly across Our Solar System is 11 light-hours across Moon is 1.28 light-seconds away (238,866 mi) Think of this when you look at the stars at night Solar Energy Sun produces thermonuclear energy Atoms of hydrogen are forced together under intense heat and pressure Pairs of hydrogen nuclei are fused and enormous quantities of energy are released Principal outputs are radiant energy and solar wind Sun has used up about of the hydrogen in its core in 5 BY, it will run out of hydrogen fuel Sun provides Earth with radiant energy, which travels to Earth at speed of light This energy flows outward from the sun in the form of electromagnetic waves Only a tiny fraction of suns energy output is intercepted by Earth about one/two-billionth Solar energy that reaches the Earth is termed insolation Solar constant = average value of insolation received at thermopause = 1372 W/m 2 Electromagnetic Waves Electromagnetic waves classified on the basis of wavelength the distance from the crest of one wave to the crest of the next Hot bodies radiate (mostly) shortwaves Cool bodies radiate (mostly) long waves Wavelengths are measured in micrometers Dividing line between shortwave and long-wave radiation is about 4 micrometers (&m = 1 millionth of a meter) Suns energy in ultraviolet, visible and shortwave infrared portions of spectrum Earth outputs heat to outer space in longer wavelength, thermal infrared waves Solar and Terrestrial Energy Distribution of Insolation Angle of solar rays varies by latitude uneven global distribution of insolation Subsolar point = receives insolation perpendicular to the surface (sun is directly overhead) = remember well at Syene Subsolar point ranges from 23.5 o N to 23.5 o S Tropics receive more concentrated insolation due to the Earths curvature Tropics receive 2.5x more than poles Global Net Radiation Net radiation is balance between incoming shortwave and outgoing long wave...
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- Spring '08