Re: Planets and Moons

> > I think I read somewhere, perhaps in one of the replies to this thread, that
> > it _is_ possible-- the two planets have to orbit a common point, which in
> > turn orbits their sun...but I suspect it requires some fairly heavy
> > math/physics to figure out.
> I've read this as well. If the two are smilar in size and mass, then
> you'd get them orbiting a common center of gravity. That would lead to
> some interesting days and nights, I suppose!
It's just Keppler's laws that dictate orbital mechanics, and they
apply to unary and binary, star and planet orbiting systems alike.
All bodies, like our Sol and Earth are in fact orbiting each other.
While Earth's ellipse is far more dramatic, Sol's center actually is a
little bit eccentric.  That being said, Sol's orbit is well within the
boundaries of its corona.  Skip the math and physics and think about
what happens when you swing a younger sibling (or a dwarven friend)
around.  Your sibling rotates around you, but in turn, your center of
mass (say, your torso), spins too.

The majority of star systems in our galaxy are binary star systems.
That is, these systems have two stars orbiting a common center of
mass.  It's quite common for one of these stars to be an invisible
black hole.  Some hypothesize that if conditions had been subtly
different, Jupiter may have had enough mass to support a sustained
fission/fusion reaction and our days and nights would have been quite
effectively messed up.  Arguably, Earth wouldn't be able to sustain
life under such conditions.

That being said, I say leave planets and stars to the paperback
science fiction nerds.  My constructed world doesn't use Newton's mass
and gravitation correlation, so planets can't form in the sense they
do in our universe.  I have this crazy notion: consider a cylidrical
universe.  At equally spaced intervals along the cylinder are double
sided, circular sheets.  All life in this world exists on the surface
of these sheets.  Furthermore, the walls of the cylinder aren't really
boundaries.  If a creature on one of these planes were to walk for a
time in one direction, they would eventually return to the position
they started.  So, from any given vantage in the world, you can
imagine you're in the center of the universe and that if you traveled
to the edge, you would actually be right back where you started.  The
planes form because gavitation in this universe is a function (a
tangential function) of position along the axis of the cylinder.  It
gets weirder...  Light doesn't travel in straight lines, in fact, it's
bound to the same rules of gravitation as massive objects.  For this
reason, when you are on the surface of any of these planes, you appear
to be in a Deisen sphere (an inside out planet) and above you is a
single 'moon', which is the neighboring tier.

If that doesn't give you nigthmares...well...have fun anyway.  :-)

Kris.
--
(watch the reply to)