Re: CONCULTURE: dual planets

First things first - I think the tidal effects are going to be ginormous.  This
will effect the crust as well as the liquid surface.

I once postulated a twin planet with one planet roughly 1.35 Earth Masses and
the other about 2.01 EM - the 2.01 EM was mostly covered in deep ocean, at least
twice as much water as the Earth, with a huge set of volcanic plateaus facing
the second planet.  The mass was in towards the common mass centre, and the
libration and precession and similar effects meant that it remained volcanically
active, care of the tides.

Ditto for the smaller planet.

I also envisaged a pair of planets about .87 EM and .45 EM.  The smaller one was
largely dust, and the larger one had a much wetter surface.  Again, the tides
played a large role in events.  The smaller one had huge dust tides, which the
inhabitants didn't much like.  The larger one had more dry land than Earth, but
still faced relatively huge tides.  Ditto for vulcanism.

As far as I can see, the day would be longer, because both planets, if close
enough to be a double planet, would be tidally locked to each other.  That's
inescapable.  At the proper distance - which I used to know but have since
forgotten - the orbit would decay at much the same pace as the Earth-Moon orbit.

But I suspect Michael will be able to provide more compelling science than my
mere recollections and ideas.

Wesley Parish

Quoting Sally Caves <scaves@...>:

> ----- Original Message -----
> From: "Michael Poxon" <m.poxon@...>
>
> > If you're positing a planet with more than one moon and don't want
> tidal
> > effects to be disastrous, the main criterion is mass,
> > bearing in mind Newton's gravitation equation. All the examples we
> have of
> > multiple, high-mass moon systems revolve around
> > vastly more massive gas giants where your damgerously-high-tide
> effects
> > don't matter. Mars has two moons but they're both tiny
> > and would have a negligible effect on any Martian ur-water/life.
> > You may also want to consider the fact that on a planet with a
> massive
> > multi-moon system (because of the effects you describe)
> > landbased life may simply not have been able to evolve in the first
> > place -
> > I don't know, I'm an astronomer rather than a biologist!
> > Mike
>
> Sorry to be tuning in so late to this!
>
> Mike, if you're an astronomer, perhaps you could tell me if it's
> possible to
> have two planets revolving around one another (roughly earth size), if
> this
> is astronomically possible, how far apart they would have to be, how
> big
> each planet would look in the sky to the other, whether there would be
> orbital decay that would threaten both worlds, and whether there would
> be
> disastrous tidal effects on both worlds. I've been considering this kind
> of
> system for a world I'm designing. I had the vivid image of the remains
> of
> dead cities stretching far out into the wet horizon, visible only a low
> tide, that would be flooded with water when the tide came crashing in;
> land
> masses that had cliffs, living cities moving further and further back as
> the
> tide ate away at the coast line. But I am decidedly NOT an astronomer,
> so I
> don't know my physics, although I do read quite a lot about astronomy,
> but
> as a rank amateur. Would you be able to advise me?
>
> yry wemry eftoihs! Sally
>
>
>
> > ----- Original Message -----
> > From: "Sylvia Sotomayor" <kelen@...>
> > To: <CONLANG@...>
> > Sent: Monday, November 15, 2004 5:39 PM
> > Subject: Re: CONCULTURE: First thoughts on Ayeri calendar system
> >
> >
> >> On Monday 15 November 2004 08:53, Roger Mills wrote:
> >> [lots of interesting stuff on moons & planets]
> >> > Well, make that "18 to 70" for Carsten/me, respectively...:-)
> Neither
> >> > of
> >> > us, alas, seems to be near a university. It appears we could both
> >> > profit
> >> > from some good help and advice-- if either of you gentlemen are so
> >> > inclined. Do you know of anything useful (intelligent-amateur
> level)
> > that's
> >> > on-line?
> >> >
> >> > Since this is basically Off-Topic, best if we discuss privately.
> >> >
> >> Not too off-topic! I've been following the discussion, since I'd like
> to
> > have
> >> 4 moons for Terjemar. But beyond some basic calculations, I haven't
> >> progressed very far in determining size, distance, orbits, tides,
> etc.
> >>
> >> -S
> >> --
> >> Sylvia Sotomayor
> >> sylvia1@ix.netcom.com
> >> kelen@ix.netcom.com
> >>
> >> Kélen language info can be found at:
> >> http://home.netcom.com/~sylvia1/Kelen/kelen.html
> >>
> >> This post may contain the following:
> >> á (a-acute) é (e-acute) í (i-acute)
> >> ó (o-acute) ú (u-acute) ñ (n-tilde)
> >>
> >> áe ñarra anmárienne cí áe reharra anmárienne lá;
> >
>


"Sharpened hands are happy hands.
"Brim the tinfall with mirthful bands"
- A Deepness in the Sky, Vernor Vinge

"I me.  Shape middled me.  I would come out into hot!"
I from the spicy that day was overcasked mockingly - it's a symbol of the
other horizon. - emacs : meta x dissociated-press

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