243.01 Earth day sidereal periods of
Venus does the transit cycle take? Why, 365.24 of them,
which happens to be the number of days in the Earth
year, just as 243.01 is the number of Earth days in the
Venus day.
Personally, I find that just plain spooky. Officially, these
coincidences are just that: coincidences. The Earth and
Venus are not in an 8:5 resonance, officially, yet when you
either regress or progress the orbits, these regularities
do not go away. They drift in and out of greater or lesser
regularity for as far as the floating point calculations can
go, for millions of years, without any divergence. It is an
extremely stable configuration.
There was a lot of argument in the 1960's about whether
this was really a resonance or not, and by the 70's, it was
branded an annoying coincidence. Personally, I think it's
too neat to be a coincidence, so I was cheered last year when
I ran across a AGU paper that calculated that the differences
between the atmospheric tidal torques and the solid tidal
torques generated by Venus's tiny eccentricity acted to push
Venus back and forth and avoid the adjacent two planets
falling into a recurring perfect face-to-face lock, Venus with
the Earth, by minutely altering the length of Venus' day!
I stand on spooky as the best description of the
universe. Oddly, shifting from one dangerous situation
to another makes life in the universe fairly safe. The danger
in a dangerous situation is that you stay in that situation.
If two planets have a resonant lock and keep meeting
face-to-face, the two will increase the eccentricity (but
not the period) of each other's orbit by the slow repetition
of tugging at each other every close pass, making each
successive pass closer and closer and closer... So it's a
good thing that something always messes up that doomed
arrangement, like the meddling of Jupiter.
These articles about simulations are always interesting,
but there are always things that can get overlooked. Take
the solar wind. Among other things, when you calculate
backwards, you have to keep changing the mass of the
Sun! The solar wind carries mass away from the Sun so
that it becomes progressively lighter over long timespans.
You have to work out the rate of mass loss and keep
adding that mass back into the Sun as you go back
millions, even billions, of years in time! This constantly
changes the central force in your motion equations.
I don't doubt the calculations... exactly. The principal,
Laskar, has been doing these simulations for more than
20 years. He says an Earth-Venus bump is the most likely
bad news (and that's obvious without a super-computer).
They say their model is more accurate because Laskar
and Gastineau's model relies on non-averaged equations and accounts
for general relativity. Well, their model is not the first to
account for general relativity. The reason that they present
the results of many runs of their model is this: even though
the math is now accurate enough to calculate long periods,
every few million years (about 12) you run into a chaos
bottleneck, a divergence, which is a fork in the road with
a 50%-50% chance that one of two paths is correct.
What they have done is flipped a coin every 12,000,000
years or so and gone on, then repeated the run and gone
the other way this time, with each divergence. So they
get statistics, not certainty. 12 times out of 2500 times,
the Earth did such and so, they say. What does that
prove? Anything at all?
There is no certainty. On the micro-scale, the universe
is quantum chaos. Particles tunnel right through force
barriers by de-materializing and re-materializing on the other
side. Electrons act like waves one minute and then turn into
particles the next instant. God plays dice with the universe;
matter transforms at random. It's a mess, Lord.
On the macro-scale of everyday life, the universe is
deterministic. My computer works (most of the time); my
car engine runs; gravity always makes things fall at the
same accelerated rate. Objects that act like particles never
turn into waves and vanish -- Phfft! It's so orderly.
But on the super-macro-scale of deep space and deep
time, the universe goes back to being in a state of quantum
chaos at a long slow pace, seemingly deterministic until it
goes just as random and whacky as the micro-scale universe.
As for the solar system, enjoy it while it lasts.
Sterling K. Webb
-
- Original Message -
From: Charley cm...@columbus.rr.com
To: meteorite-list@meteoritecentral.com
Sent: Thursday, June 11, 2009 11:49 AM
Subject: [meteorite-list] Future Planetary Collision?
Hi List,
Maybe a bit off topic although lots of meteoroids would be created.
A French researcher says we may have a collision with Venus or Mars in
3.5 billion years.
http://www.chinadaily.com.cn/world/2009-06/11/content_8271159.htm
Best regards,
Charley
Well, squids
