Astronomy

Geocentric- Earth centered system developed by ptolemy //**
 * //Solar System Models
 * was accepted until 1960's
 * Heliocentric-**sun centered system developed by Copernicus


 * Celestial Objects-**objects observed in the sky during the day or night. (Planets, Sun, Moon, Stars...)
 * **Constellation**-a group of stars that make an identifiable pattern in the sky


 * Rotation-**spinning about the North and South Axis
 * __evidence__**-
 * the apparent daily counter-clockwise motion of celestial objects around Polaris (north star) is because of earth's rotation toward the east. (rate=15 degrees per hour)


 * solar day-amount of time required for the Earth to rotate from one noon to the next (15 degrees x 24 hours=360 degrees)


 * Coriolis Effect-**horizontal deflection undergone by all moving materials on the Earth's surface
 * Northern Hemisphere-things are deflected to the right (clockwise)
 * Southern Hemisphere-deflected to the left (counter-clockwise)


 * Foucault Pendulum**-an experiment to demonstrate the rotation of the Earth

Evidence: **
 * //Revolution-// a slightly elliptical orbit around the sun (counter clockwise) [365.25 days for one revolution]
 * seasonal changes of the constellations
 * solar diameter varies in a cyclic pattern
 * **Perihelion** - sun is the largest, occurs in the N.H. winter (shortest distance between the earth and Sun)
 * **Aphelion -smallest, occurs in the N.H. summer (largest distance between the Earth & Sun) **

Seasons //The Earths tilt is 23.5 º Parallelism of the Earth's Axis- The Earth axis remains parallel throughout its revolution around the sun. (23.5 º N or S of the equator)**
 * Local Noon-**when the sun reaches its maximum altitude
 * Zenith-**the point directly overhead
 * the suns rays can only be directly overhead at solar noon between the tropics

Equinox-// the sun is in the zenith position at the equator (March 21st and Sept. 23rd) 12 hours of both daylight and darkness //Summer Solstice-// the sun is in the zenith position at the tropic of cancer (June 21st)/ Longest amount of daylight of the year in the northern hemisphere
 * //Winter Solstice-// the sun is in the zenith position at the tropic of Capricorn (Dec. 21st)/ Shortest daylight of the year in the northern hemisphere **