December 6, 2011

• Objective• Determine the eccentricity of orbits• Agenda• Sun Path Lab

– Part A• Eccentricity notes• Ellipse Lab

ECCENTRICITY

REVOLUTION OF THE EARTH

• Earth's orbit around the sun is a closed curve called an ellipse.

Eccentricity

• A number that shows how round or flat an ellipse is. – A perfect circle = 0– A straight line = 1

Eccentricity is d divided by L. d/L

d= distance between foci

L= length along horizontal axis

VARYING DISTANCES OF THE EARTH

FROM THE SUN• We are closest to the sun on January 3

and furthest away on July 4 due to the elliptical shape of our orbit.

Eccentricity of Earth

• .017– it is nearly a perfect circle. – The sun's apparent diameter will look largest

on January 3 and smallest on July 4.

ORBITAL SPEED– January 3rd: Highest orbital speed, highest

kinetic energy, lowest potential energy

– July 4th: Lowest orbital speed, lowest kinetic energy, highest potential energy