This picture records the sun's position in the sky, each two weeks at the same time. Is this picture showing the elliptical path of the sun over a period of a year or is this picture decribing some other aspect of the sun's orbit.

The seasons are coursed by the Earth's tilt. I think the picture you provide, which is great by the way, provides evidence of this as well as the eccentricity of the Earth's orbit.

 

I am sure you can find out more by doing a quick google.

Edited July 31, 201015 yr by ajb

It's known as an analemma: http://en.wikipedia.org/wiki/Analemma

 

It is caused by both the eccentricity of the Earth's orbit and the axial tilt of the Earth.