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Solar System: Planets !% Chance of CollidingFrom: Michael Winn
Subject: Philosophy
Date/Time 2009-06-12 03:57:56
Remote IP: 74.162.17.113
Messagenote: this will be of special interest to Greatest Kan & Li adepts working with the planets. 1% chance suggests great instability in what many believe to be inviolable.
michael
SOLAR SYSTEM'S PLANETS COULD SPIN OUT OF CONTROL
By Stephen Battersby
New Scientist
June 10, 2009
http://www.newscientist.com/article/mg20227125.000-solar-systems-planets-cou
ld-spin-out-of-control.html
The solar system's clockwork motion is by no means guaranteed: one day the
Earth could collide with Venus or tear Mars apart in a close encounter, a
new simulation has shown.
We know that the apparently reliable orbits of the planets are unstable in
the long run, because their weak gravitational effects on one another can
add up in unpredictable ways. Technically, the system is chaotic. Could this
very mild chaos lead to disaster?
Mercury is the key to catastrophe. It is especially susceptible to Jupiter's
influence because of a small celestial coincidence: Mercury's perihelion,
the point where it gets closest to the sun, slowly moves around at a rate of
about 1.5 degrees every 1000 years, and Jupiter's perihelion moves around
only a little slower. One day, the two will probably fall into sync, at
which time Jupiter's incessant gravitational tugs could accumulate and pull
Mercury off course.
A study led last year by Jaques Laskar of Paris Observatory in France found
a slim chance that Mercury's orbit could be pulled into a highly elongated
ellipse, putting it on a potential collision course with Venus. That work
used a mathematical trick to calculate average changes over many planetary
orbits, so the method was limited. "Close to a collision, it loses its
validity," says Laskar. He and his colleague Mickaël Gastineau have taken a
more thorough approach by directly simulating 2500 possible futures,
calculating the planets' orbits over 5 billion years, up to when the sun
turns into a red giant.
Each of the 2500 cases has slightly different initial conditions --
Mercury's position varies by about 1 metre between one simulation and the
next. In 20 cases, Mercury goes into a dangerous orbit and often ends up
colliding with Venus or plunging into the sun. Moving in such a warped
orbit, Mercury's gravity is more likely to shake other planets out of their
settled paths: in one simulated case its perturbations send Mars heading
towards Earth.
Laskar found that Mars could hit Earth directly, be thrown out of the solar
system, or come so close that Earth's gravity would tear it into pieces
which would rain down on our heads. Alternatively, the orbits of the inner
planets could be scrambled, so Earth collides with Mercury or Venus.
"We now have the definitive answer on solar system stability," says Gregory
Laughlin of the University of California at Santa Cruz. Fortunately, the
chance of the inner solar system one day going haywire is only 1 in 100.
- Solar System: Planets !% Chance of Colliding: (322) Michael Winn (1575) - - 2009-06-12 03:57 am
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