Path of the Moon

I thought this was kind of neat. Not because it's particularly exciting or insightful, just because it's something that pertains to our (semi-) every-day lives (as close as one gets when talking about astronomy, I suppose), and we (or at least I) never really think about it. Off the top of my head I wouldn't really think of the moon's orbit in this shape.

Obviously this is not to scale. But the point is that if I had drawn the moon's orbit without really thinking about it, it would have come out something like:

Which is not actually the case. The orbit of the moon is actually a thirteen-sided... uh... polygon? I don't know what you'd call it. Anyway, it looks more like a circle, to scale. You might expect it to be 12 sided, for each of the months, but due to the fact that our calendar does not perfectly match the phase of the moon, it's more like 13. Anyhow, if you tweak the parameters so that you can actually see the shape, rather than a circle, you get this:

Which seems totally counter-intuitive!

References:

Helmer Aslaksen - National University of Singapore