wrote:

[snip]

(2) (Shorter question) If I straighten out the Earth's
revolution around the Sun so it's a straight line, what curve is
the Moon's motion along that line most similar to, perhaps a
sine wave? I know it's actually an incredibly complicated curve
but that's the general shape of it, i.e. there are no little
loops or sudden changes of direction?


(I can't help much with the first question, except that I believe the
lava flows producing the maria are thought to have been triggered by
impacts rather than vulcanism.)

Your sine-wave idea is pretty much correct; the Moon traces out a
path that's essentially an ellipse with gentle sinusoidal 'wiggles',
having no loops or reversals. The Earth does too, under the Moon's
influence, but the waves are much smaller, with an amplitude less
than the planet's radius. Meanwhile the centre of mass of the
Earth-Moon system follows a near-perfect ellipse. Note that the
Moon-Sun distance increases by only about 1/200 AU between the New
and Full phases, while the Earth and Moon cover something like 1/4 AU
in their orbit during the same interval, for an average 'slope' (in
radial motion _vs_ tangential) of only about one part in fifty.

--
Odysseus