Re: [lojban] Re: Lojban Kids Show - location

[Pierre Abbat <phma@phma.optus.nu>]

On Thursday 22 July 2010 08:22:09 CosmicRay wrote:
> OK we've had two compelling votes to place Lojgugde at Earth-Moon L4/L5,
> which for all practical reasons are ideal.  Can anyone tell me how
> frequently and for how long Lojgugde at one of these points may be in
> Earth's or the Moon's shadow?  The Moon's orbital period is ~27 days and is
> off Earth's equatorial axis by ~5°.

Lojgugde would be in the Earth's shadow as often as the Moon is eclipsed, 
which is about twice a year, and in the Moon's shadow as often as an eclipse 
of the Sun passes through the middle of the Earth, which is somewhat less 
often. (There may be five solar eclipses in a year, but they pass over 
different parts of the Earth.) Both occur when the Sun passes through the 
plane of the Moon's orbit. L4 is eclipsed by the Moon 1/6 through a lunation 
(starting at the dark, not new, moon) and by the Earth 1/3 through a 
lunation. L5 is eclipsed by the Earth 2/3 through a lunation and by the Moon 
5/6 through a lunation.

> From the story's perspective it's less ideal; placing the station at those
> points would make it visible to the naked eye at certain times.  When the
> station is just past parallel to, through to behind the Earth (relative to
> the Sun) and back again, the spinning mirrors would glint, causing a
> pinpoint of flashing light in the sky with a frequency of about 30 seconds.
>  For a little under half its orbital period the flash may be visible from
> Earth at dawn and dusk and would certainly be easy to see at night.

The mirrors are aimed to reflect sunlight into the station's windows and onto 
the opposite land. They wouldn't be visible from Earth. Other surfaces of the 
station could be covered with matte solar panels or some such.

By the way, how did you get a line beginning "From " past the mail server 
without it adding a greater-than sign?

Pierre
-- 
Jews use a lunisolar calendar; Muslims use a solely lunar calendar.

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