[Dragaera] Fwd: Moon(s) and Tides (was Re: Jhegaala etc.)

[Ken Koester]

Jon Lincicum wrote:

>The other compelling argument for a moon, however, is the presence of life on Dragaera. It is undeniably the case that without the moon on Earth, life could not have evolved here. Not just due to tides, but also because the moon helps stabilize our orbit, and maintain the planet's rotational speed. Without the moon, the axial tilt of earth would long ago have evened out to be perpendicular to the plane of the Solar system, meaning we would not have seasons. 
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Ah--that is hardly undeniably the case, I believe.  The moon does 
nothing to stabilize our orbit; note that Mercury & Venus manage just 
fine without moons, & Mars isn't going to see anything noticeable from 
Deimos & Phobos.  Even worse, a moon would offer very little protection 
from a wandering Jupiter; maybe, as a sort of 3-body problem, but 
probably not, considering the disparity of masses.  And far from 
maintaining our rotational speed, the moon slows us down by several 
milliseconds a year; a day during the age of dinos was considerably 
shorter than it is now.  In the distant future, the earth will become 
tidally locked to the moon & a "day" will be as long as it takes for the 
moon to complete an orbit around the earth.  And I don't see any reason 
at all for the axial tilt of the earth to change absent a moon.  It's a 
gyroscope, after all, and there aren't any forces operating to change 
it, with or without moon--again, check moonless or effectively moonless 
planets w/ considerable axial tilts.  And if the axial tilt was zero, 
there would still be seasons due to the eccentricity of the ellipse; 
they just wouldn't be as pronounced as they are now (& not the 
same--you'd get "summer" and "winter" at the same time in both 
hemispheres & it would be reversed from what it is now in the northern 
hemisphere; our summer currently starts at aphelion).

>There are clearly seasons on Dragaera.  And from observations about planting/harvesting times and such in various books, they appear to be quite similar to ours. 
>

I don't recall winter, however. . . .

Snarkhunter