Re: Fw: [FT] Islamic Federation ships and request to Nyrath

On Tue, 24 Aug 1999, Laserlight wrote:

> Tom A said:
> 
> >in any case, if a planet is end-on, it has permanent night
> and permanent
> >day areas, just like a tide-locked planet, even if it isn't
> tide-locked.
> 
> No.  A tide locked planet (tide locked through the north
> pole, say) would present the north pole to the primary at
> all times.  A planet which is (as Tom puts it) "end on"
> would present the north pole in the same direction all the
> time, but in reference to the universe at large, not the
> primary (in the same way the Earth's pole always points
> towards Polaris).

i'm evidently not having a good day today.

Roger wasn't referring to this case, though: he specifically said "it
doesn't have to be tide-locked to the sun". but still.

i am having a slightly hard time imagining a planet with spin axis
parallel to the ecliptic and which is tide-locked to the sun: it would
involve the axis changing direction relatively rapidly (a comlete
circuit
once a year). this means that the tidal force on the planet is enough to
overcome the precession effect due to the planet's angular momentum (my
physics being rather lacking, i lack the words to describe this
properly).

given the size and mass of a planet, that is a very large amount of
momentum, and consequently would require huge tidal forces. i'd be
skeptical about such a configuration being possible for a planet of
habitable size (although i have a very strong suspicion i'm about to be
proven wrong!).

tom