PHY121 Ch 3 Notes

PHY121 Ch 3 Notes - Astronomy Chapter 3: Cycles of the Sky...

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Astronomy Chapter 3: Cycles of the Sky The rotation of Earth on its axis produces the cycle of day and night, and the revolution of Earth around the sun produces the cycle of the year. Because Earth orbits the sun, the sun appears to move eastward along the ecliptic through the constellations completing a circuit of the sky in a year. The locations of the sun and planets along the zodiac are bases for the ancient pseudoscience known as astrology. The planets orbit the sun almost exactly in the plane of the Ecliptic. The moon orbits Earth in almost the same plane. Seasons: Because the ecliptic is tipped 23.5° to the celestial equator, the sun spends half the year in the northern celestial hemisphere and half in the southern celestial hemisphere. In the summer , the sun is above the horizon longer and shines more directly down on the ground. Both effects cause warmer weather in the northern hemisphere. The sun’s path is north of the celestial equator (in northern hemisphere). It is most north at summer solstice. In the winter, the sun is in the southern sky (south of the celestial equator in northern hemisphere), and Earth’s northern hemisphere has colder weather. For equinox , the sun’s path is along the celestial equator. The seasons are reversed in Earth’s southern hemisphere relative to the northern hemisphere. The beginning of the spring, summer, winter, and fall are marked by the
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This note was uploaded on 12/11/2011 for the course PHY 121 taught by Professor Weinstein during the Fall '08 term at SUNY Buffalo.

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PHY121 Ch 3 Notes - Astronomy Chapter 3: Cycles of the Sky...

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