Double planets

Peter Westlake · 13 Jul 1998, 12:37 · from whorl-v0008.mbox · original

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From: Peter Westlake <peter at harlequin.co.uk>
Subject: Re: (whorl) Double planets
Date: Mon, 13 Jul 1998 13:37:46 +0100
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At 22:09 1998-07-09 -0700, prion wrote:

>Also, it's probable that the Whorl is parked in one of the Lagrange
>points of Blue and Green, where their mutual gravitational attraction
>on it cancel each other out, and it remains at rest with no power
>being needed to maintain orbit.  Otherwise, it's unlikely Horn would
>be able to pick it out among all the other stars unless it was always
>visible and near.  It could be always visible because it's orbiting
>Blue, but it wouldn't be, because it took three days on the course
>toward Blue for it to become obvious that that was their destination.=20
>If the Whorld were in orbit, it would be apparent immediately.  If it
>weren't in a Lagrange point, it would be very unlikely for an inhumu
>to pass in front of it while flying, as Horn seems to think occurs.

Unfortunately, I don't think Blue and Green *have* a Lagrange point.
Hal Clement has a short story called "A Little Knowledge", in which
a fleeing criminal parks his spaceship what he fondly imagines is
a Lagrangian point of a double star. But the two stars are too closely
matched in mass for it to work: one mass has to be considerably bigger
than the other. (If anyone has the story, and the ratio is 25.8 : 1,
then I shall appear very clever; if it isn't, well, how can I be expected
to remember a detail like that?) The story ends with the fugitive
finally getting round to looking out of the window, to find himself
plunging into one of the stars as it orbits towards him.

Whatever the masses of Blue and Green may be, it isn't very likely
that they could differ enough to have Lagrangian points while both
being reasonable places to go and live.

SBear.

*More Wolfe info & archive of this list at http://www.moonmilk.com/whorl/

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