[meteorite-list] INNER SOLAR SYSTEM

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun Sep 24 21:56:35 2006
Message-ID: <002701c6e045$d08b8e90$be7f4b44_at_ATARIENGINE>

Hi,

    We all know the orbits of the planets vary slightly. The
obliquity, or tilt of the Earth's axis oscillates from 22.1?
to 24.5? in a 41,000 year long cycle, as does orbital
inclination, and the orbit's eccentricity has a small variation
over a 102,000 year cycle from almost zero to 0.070. The
equinoxes precess in a 23,000 year cycle. As you can
tell, these numbers don't change that much, so things
should appear to be pretty calm.

    The other planets in the inner solar system go through
similar cycles, equally non-dramatic, although I vaguely
remembered that Mars was a bit more extreme than the
rest of us. It doesn't seem like it would be very dramatic
or exciting to watch, if you could watch it change. Then,
I watched this movie of the inner solar system's orbital
evolution over the last 3,000,000 years:
http://muller.lbl.gov/pages/innerplanets.html or directly
from here: http://muller.lbl.gov/images/inner.mov

    The movie that you can view or download from this
page is about 12 Mbytes long, and in .mov format. I
used QuickTime Player (.mov is its native format) because
you can step through it frame by frame (right/left arrows).
Real Player and Windows Media Player (10) will also play it.

    The scale of the animation is not exaggerated or amplified.
If you could sit in space and watch the inner solar system
trace each orbit with a visible line, this is what you'd see.
The units on the edges of the background plane are AU's.
The site rather modestly says, "Even if you are an expert,
you may be surprised at what you see!"

    "Astounded" is more the word that comes to my mind.
"Drunk drivers at NASCAR track" would be a good title,
if you pasted in some little cartoon racers with sponsor
patches. Is this the renowned "stability" of the solar system
we hear so much about?

    And, of course, it IS stable. Nothing has gone wrong in
the last three million years nor for a long time before that.
Still, everything wobbles like crazy...

    Currently, Venus can approach as close as 24.7 million
miles and Mars as close as 34.7 million miles, but it would
seem that in the past (and future too) their close approaches
could be as near as roughly half that distance.

    I found this movie to be utterly fascinating (could be just
me). After a few times through it, I would concentrate on
just watching one planet at a time: Mercury slides back and
forth like it was shifting the Sun from one elliptical focus
point to the other; Mars' orbit expands and contracts; Venus
and the Earth pull up close and flirt with resonance lock; they
all rock back and forth.

    As with any good movie, I was disappointed that it was
"only" three million years long.


Sterling K. Webb
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Received on Sun 24 Sep 2006 09:56:27 PM PDT