Subject: Is earth's orbit a helix ?

Textbook diagrams show earth's orbit as a near-circular ellipse. But, since the 
sun is moving, wouldn't the orbit of the earth (and all the planets) actually 
be helical? Picture a light spot on the rim of a bicycle wheel in motion. The 
sun is the center of the wheel, and the earth is on the rim. A time exposure 
over a year would show something like a cycloid or a helix. 

Re: Is earth's orbit a helix ?