Re: poly: Re: the Moon and life on Earth

CurtAdams wrote:
>
> In a message dated 1/19/98 12:55:22 PM, carlf@atg.com wrote:
>
> >>(Having a large moon has
> >>sometimes been cited as a 'reason' for Earth to be fecund.)
> >
> >By whom, and on what grounds? I read this in a Larry Niven story years
> >ago, but I don't recall seeing it anywhere more authoritative.
>
> I saw it in a tertiary source a while back. The reason is that
> the moon stabilizes the Earth's axis of rotation. Without that
> stabilization the axis drifts widely over time, including sometimes
> tilting at 90 degrees like Uranus right now, which is thought
> incompatible with complex life.

 The hypothesis I heard a long time ago had to do with the tidal effects
on estuaries/ coastlines. It may have had more to do with creatures
leaving the sea than with single-cell life.

I'm not so sure about the axis-stabilization theory, that the Moon
is necessary. I suppose it would provide some stability by creating
a tidal bulge, which produces an oblate spheroid rotating about its
smallest principle axis (a minimum energy configuration).
But where is the perturbation for a 90 degree knock down of a moonless
Earth?

Uranus has probably been that way since shortly after the formation
of the Solar System. A friend of a friend (whose name I can't
remember right now) is working on a beautiful theory for this,
to the effect that a tilted (to Uranus' orbit) disk of material
existed back then, of which Pluto/Charon might be a remnant. Twice
each Uranus year, the planet moved through the disk. The relative
motion causes material from the disk to be preferentially deposited
near the poles of an 'upright' planet. If the nodes of Uranus' orbit
don't precess
too much over the relavant time scale, this produces the required
angular momentum component.

-- 
Forrest Bishop
Chairman,
Institute of Atomic-Scale Engineering
http://www.speakeasy.org/~forrestb