posted on Nov, 29 2009 @ 10:55 PM
reply to post by whiteblack
June 21st is on the upper-left. December 21st is on the lower right. March & September 21st are half-way between them.
Does this shape look familiar? It should; most globes have it drawn on the side. It's called the "analemma" and it shows what latitude the sun is
over on each day of the year.
As the sun appears to move north & south in the sky according to the seasons, this defines to long-axis. Of course, it's actually the Earth that's
moving around the Sun. If the Earth moved in a perfectly circular orbit (and thus at a constant speed), then the analemma would be a straight line.
Instead, the Earth moves in an elliptical orbit and - as Kepler demonstrated 400 years ago - changes speed; faster when it is closer to the Sun
(perihelion is in early January) and slower when it is further away (aphelion is six months later, in early July). Because the Earth rotates on its
axis at a [reasonably] steady rate, but changes speed as it orbits the Sun, this means that the Sun is not exactly synched-up with the clock. Thus,
sometimes the Sun is highest in the sky a little before noon, and sometimes a little bit after. That's why you get the little side-to-side motion
that makes the analemma look like a figure-8, instead of a straight line.