December 6, 2011
• Objective• Determine the eccentricity of orbits• Agenda• Sun Path Lab
– Part A• Eccentricity notes• Ellipse Lab
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