Planetary Motion Kim Lachler Updated 8/14 NCES:6.E.1.1

Rotation Planets spin around an axis 1 rotation = 1 day

Rotation Planets are different sizes and rotate at different speeds, therefore their day lengths are different. Earths rotates counterclockwise - sun appears to rise in the east

Revolution One complete trip around its orbit. Orbit – the path a body follows as it travels around another body in space one revolution = 1 year

Revolution Planets orbits are different lengths; therefore their years take different amounts of time.

The Shape of Orbits Kepler Discovered Mars orbit was an ellipse not a circle. The distance from the sun varies. The distances for the inner planets is insignificant , therefore their orbits look round. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01.cfm?chapter_no=visualization

Seasons Earth tilts by 23.5˚ changing the angle the sun hits the earth. This effects the intensity of the sun’s rays hitting the surface resulting in seasons The distance from the sun DOES NOT affect the seasons. The difference is not big enough.

Seasons Summer for us is when the Northern Hemisphere is tilted towards the sun. Winter for us is when the Northern Hemisphere is tilted away from the sun.

Seasons Equinox sun directly above equator Spring Fall

Seasons Solstice The point at which the sun is as far north or as far south of the equator as possible. Summer solstice Winter solstice – longest day light – shortest day light

Bibliography Holt, Rinehart, Winston, North Carolina Holt Science & Technology, Holt, Rinehart, Winston, Orlando, 2005 Revolution and Rotation of the Planets , http://csep10.phys.utk.edu/astr161/lect/solarsys/revolution.html, accessed 2/26/11 Google images, http://images.google.com, accessed 2/26/11