Astronomy

Solar system models Geocentric Heliocentric 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
 * Earth centered system developed by ptolemy
 * was accepted until 1960's
 * Sun centered system developed by copernicus
 * modern understanding of the structure of the universe

Rotation A 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- the amount of time required for the earth to rotate from one noon to the next 15 X 24 hours= 360.

Coriolus effect Horizontal deflection undergone by all moving materials on the earth's surface. Northern hemisphere- deflected to the right (clockwise) Southern hemisphere- Deflected to the left (counter clockwise)

Foucault pendulum An experiment to demonstrate the rotation of the earth.

Revolution A slightly elliptical orbit around the sun( counter clockwise) 365.25 Days for one revolution. Evidence: Seasonal change of the constellations the solar diameter varies in a cyclic pattern Perihelion- Sun is the largest, occurs in the N.H. winter (shortest distance between the earth & sun) Aphelion- Smallest, occurs in the N.H. summer (largest distance between the earth and sun)

Seasons the earth tilt is 23.5 Parallelism of the earth's axis- the earth axis remains parallel throughout its revolution around the sun. Local noon- when the sun reaches its maximum altitude Zenith- the point directly overhead equinox- the sun is the zenith position at the equator (march 21 and sept. 23) 12 hours of Both daylight and darkness. summer solstice- the sun is in the zenith position at the tropic of cancer(June 21) Longest daylight of the year in the northern hemisphere. Winter solstice- the sun is in the zenith position at the tropic of capricorn (dec.21) shortest daylight of the year in the northern hemisphere. The planets and the solar system
 * the sun's rays can only be directly overhead at solar noon between the tropics (23.5 N or S of the equator)