Re: CONCULTURE: First thoughts on Ayeri calendar system

> > OK, I have decided! I only want to have one moon, since Maths and
Physics
> > seem to be easier then and I'm not that good at both subjects.
>
>  well, at some points during the month (ie, when each is on the opposite
> side of the planet), the two moons would negate one another's effect upon
> the tides.
>
>  I'd be willing to help out, if you like.
As a matter of fact, when the moons are on opposite sides, the tides would
_reinforce_ one another! The side of the Earth facing away from the moon
experiences a high tide just like the side facing the moon. Low tide occurs
90 degrees from this (where the moon is on the horizon).

Regarding Earth having a second moon, if its the same as what I've read
about, its actually an asteroid that's orbiting the sun, but doing so in a
way that makes it _look_ kinda like its orbiting the Earth. And there's at
least two of 'em.

Anyway, there is a very interesting type of orbit that would allow two
moons to exist in a single stable orbit. Such a situation even occurs with
two of Saturn's moons (Janus and Epimetheus). These moons are called 'co-
orbital' (a google on that term, or on the names of the moons, should
uncover a wealth of info). Here's a link to an animation I found of such an
orbit. http://www.jimloy.com/cindy/co-orbit.htm. Also, try looking
up 'Epithemeus' on Wikipedia.

Basically, what happens is that the two moons are on almost exactly the
same orbit, so they have almost the same period. But because one is
slightly closer to the center (we'll call it moon A), it goes just a bit
faster and starts to catch up with the other one (B). But when A gets close
to B, B's gravity tugs on A which tosses into a higher orbit, which causes
it to go slower. OTOH, A's gravity tugs on B, pulling it into a lower
orbit, which causes it to go faser. Just before A overtakes B, the two
moons end up switching orbits. B is now slightly closer to the center than
A. This means that B starts to pull away from A, and eventually, B will
catch up with A from behind, and the whole situation will be repeated
again, with the roles reversed. Again, the orbits will swap, and the moons
will not collide.

This is a good example of how chaos can lead to order, BTW. In the so-
called 'three-body problem' it is impossible to solve for orbital paths
directly (you have to use numerical methods), but such stable patterns can
still arise.

WRT tides, I think the tides of such a system would not be impossible to
deal with if the _total mass_ of the two moons were comprable in effect to
our own single moon. Granted you would have some very unusual tidal
patterns. Essentially, you would have two sets of basically independent
tides that chased each other around the planet. When they started to
coincide, (giving rise to maximum tidal effects) then the tide in back
would slow down, and the two tides would seperate again. Actually, you
would also have another time of maximum tide when the two moons were on
opposite sides of the planet (In this case, the two tides would appear to
pass through each other).

The whole process of 'catching up' with each other and reversing position
would take many months (ie moon revolutions), and would depend largely on
the exact seperation between the two, as well as their masses. I don't know
if I could calculate it or not, but if you watch the animation I provided,
you can count the number of revolutions of the moons before they catch up,
and use that as a rough estimate. Also, it might be a good idea to make the
moons have about the same mass.

An interesting result could be a _rare_ 'double eclipse' where both moons
happen to be near each other during an eclipse. First one would be
eclipsed, then the other (or possibly both at once?). Cool!

HTH,
~Caleb