Re: Programming a calendar system

>>>> markjreed@MAIL.COM 4/29/2004 7:09:17 AM >>>
>On Wed, Apr 28, 2004 at 02:06:51PM +0200, Carsten Becker wrote:
>> SQRT of the 3rd power of 1.45 etc. looks very much
>> like one of Kepler's laws ... Not caring about any astronomical law I
>> set 6 days = 1 week, averagely 25,333... days = 1 month, 18 months = 1
>> year and 1 year = 456,25 days. Every 4th year one day is dropped.
>
>That particular Keplerian law tells you how long a planet's orbital
>period ("year") is, based on its distance from the sun.  If you express
>the period (commonly represented in equations by T for Time) in Earth
>years and the distance (commonly represented by R for Radius) in
>Astronomical Units, the constants cancel out and you are left with the
>very simple relation that T^2 = R^3.  You can, of course, go the other
>way as well.   In your case, you have a 455.75-"day" year, where each
>"day" is 27 "hours" of 18 "minutes" of 72 "seconds" of 1.2 SI seconds
>each.  That's a total of 19,137,124.8 SI seconds, which is about 221.5
>Earth days, which is about 0.6064 Earth year.  So the planet of the
>Aregans must be 0.6064^2^(1/3) = 0.5325 AU from their Sun.
[nitpick alert]
R=T^(2/3)
this calculates to about 0.7167 AU by my calculator. Did I do something
wrong here?
[/nitpick]

>That means
>that their Sun has to be a K-type (red) star.   Which means that their
>Sun is much bigger than ours as well as much closer to them, so would
>be much more dominant in the daytime sky.
Cool. Do you have a good source for this type of data? My conculture/
conworld needs some astronomical legitimacy, and this looks like a good
way to create it. I figure that the star of the culture is say 1.6 solar masses.
So how do I find out the characteristics of it? That is, brightness, color,
temperature, where the life zone is, etc.

>But there's no astronomical law governing the length of a rotation.
>Well, that's not quite true; there is a particular orbital distance
>called the "tidal lock radius".  Planets orbiting at that distance
>eventually become locked to the Sun like the Earth is locked to the
>moon; the same side of the planet is always facing the sun.  Which means
>that 1 day = 1 year.  For planets inside the Tidal lock radius,
>the day is actually longer than the year; this is true of Mercury
>and Venus, for instance.  Beyond that, however, there's no reason you
>can't make your days any length you want.  And "weeks" and "months"
>are purely artificial constructs that can be anything you want.
>Sure, on Earth the size of the week was inspired by the number of
>visible planets in the sky, and the size of the month by the phases of
>our moon, but there's no reason to think those things would influence the
>calendar of another species on a different planet.
Tangent: Does anyone know of any data (or speculation) about the
effects of a non-tidally-locked moon on a planet. Any different from a
tidally-locked one?

>I view astronomy as a source for inspiration rather than a constraint.
Same here. But I am just starting that process. Thus the queries. :)

[snip cool conculture astronomical description]

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