TOPIC_3_Earth_Motion_Notes.ppt
- 2. TRUE MOTIONS “Real Motions” Rotation Revolution APPARENT MOTIONS “What appears to move” Sun Stars Moon Planets
- 3. ROTATION: • The spinning of Earth on its axis. • Earth rotates from West to East (counterclockwise when viewed from the North Pole). • 24 hours (15o/hour) Drawing *!* The Earths axis is tilted 23.5o relative to the sun.
- 4. REVOLUTION: • The orbiting of Earth around the sun. • 365.26 days (1 o /day) Drawing
- 5. APPARENT MOTION OF THE STARS Daily Motions • Stars appear to move in circular paths around Polaris at a rate of 15 o/hour. • Eastward to westward. • Due to rotation. Ex: Annual Motion • Some constellation are seasonal while others can be seen year round. • Circumpolar vs. non- circumpolar. • Due to revolution.
- 12. Apparent Motion of the Sun • The Sun appears to move from east to west at a rate of 15 o/hour. • The path of the sun changes with the seasons and with latitude. • Local solar noon- occurs when the sun reaches its highest point in the sky. • Only between 23.5 N and 23.5 S will the sun ever be directly overhead! (the tropics) • The sun is NEVER overhead for an observer in the continental U.S. • See sun’s path diagram
- 17. True Motions of the Moon • The Moon revolves around Earth and rotates on its axis once every 27 1/3 days. The revolution of the Moon is responsible for….. 1. The phases of the Moon. 2. Tides 3. Eclipses
- 18. MOON PHASES • The varying amounts of the lighted moon as seen from Earth. • The period from one full moon to the next is 29 ½ days. • http://www.astro.wisc.edu/~dolan/java/Mo onPhase.html
- 25. TIDES • The cyclic rise and fall of ocean waters due to the gravitation between the Earth, moon and sun.
- 30. SPRING vs. NEAP TIDES SPRING TIDES Higher high tides, lower low tides.
- 31. NEAP TIDES: Lower high tides higher low tides.
- 48. MODELS OF THE UNIVERSE • GEOCENTRIC • Ptolemy • “Earth Centered” • Drawing: • HELIOCENTRIC • Copernicus • “Sun Centered” • Drawing:
- 50. Best Evidence of the Earths Rotation… 1. Foucault Pendulum 2. Coriolis Effect- the apparent deflection of the path of a moving object due to the rotation of Earth. • N. Hemisphere – to the right • S. Hemisphere - to the left
- 51. ORBITAL GEOMETRY Keplers 1st Law Planets orbit the sun in slightly eccentric elliptical paths with the sun at one of the foci.
- 52. Johannes Kepler
- 55. Eccentricity: • “ out of roundness” • Formula: eccentricity = distance between foci length of major axis • All eccentricity values must be between 0 and 1 (decimal)!
- 57. Kepler’s 2nd Law • A line drawn from a planet to the sun will sweep across equal areas in an equal amount of time. What does this tell us? • The closer a planet is to the sun, the greater its orbital velocity (speed).
- 58. Kepler’s 3rd Law • The period of a planet squared is equal to its distance from the sun cubed. (P2=D3) What does this tell us? • Planets that are further away from the sun take longer to revolve.
- 59. Perihelion • The point in a planets orbit when it is closest to the Sun. • Around Jan 4th Aphelion • The point in a planets orbit when it is furthest from the Sun. • Around July 4th