[meteorite-list] Future Planetary Collision?

From: Charley <cmb62_at_meteoritecentral.com>
Date: Thu, 11 Jun 2009 18:22:16 -0400
Message-ID: <E599B5A94F374C99AB648AC8E557E1D5_at_HAL1>

Hi Sterling,

Thanks for the links and also all the information you provided. The movie is
astounding to say the least but even more
amazing to me is the "spooky" part about the (non-official) resonance
between Venus and The Earth. Wow!

Thank you very much for the in depth explanation-I'm sure it took you a lot
of time and trouble to put it together and I
really appreciate the information.

I learn a lot from this list!

Best regards,

Charley

"Well, squids don't work. Hey! Let's
  try elephants !"

                    Hannibal

Sterling K. Webb wrote:
> Hi, Charley, List,
>
> I'd just spotted the same press release
> (it turns out) on Space.com:
> http://www.space.com/scienceastronomy/090610-planets-colllide.html
>
> The wobbly behavior of the Inner Solar System
> is not a new discovery. Here's a movie of the inner
> solar system's actual orbital evolution over the last
> 3,000,000 years:
> http://muller.lbl.gov/pages/innerplanets.html
> It can be downloaded 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. You can open it
> in a browser window if you have the Quick Time
> plugin (takes a bit to download).
>
> 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!"
>
> "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 (or has it?). Still, everything just
> 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.
>
> Venus is the one that worries me. The orbit of
> Venus has peculiarities, too. Venus's "year" is 224.7
> Earth days. Venus's "day" is 243.01 Earth days. But
> because Venus's axial rotation is backward measured
> against the Sun and stars, the Venusian "solar day"
> is only 116.75 Earth days long. Of course, we could
> just as well not describe Venus's rotation as "backward,"
> but just consider that Venus rotates "normally" but
> with its axis turned completely upside-down, by 177.4
> degrees! However you look at it, Venus is the only body
> of any size in the solar system to rotate "backward."
>
> If you regard "normal" rotation as required, as it is,
> by most theories of solar system formation, then you
> have to invoke a Big Whack to turn Venus upside-down!
> That would have to be one heck of a whack, too. The
> energy transfer would be so great it's hard to imagine
> the planet could have survived it.
>
> So, there's another theory: that the solar tides on the
> thick atmosphere have braked Venus down to a standstill
> and are now spinning'er up in the backward direction.
> Myself, I think the atmospheric torque is just not big
> enough to do the job, and since what little we know about
> the surface of Venus suggests that there are virtually no
> winds at all at the surface (and you have to have wind to
> apply atmospheric torque to the surface), I think it's hooey.
> The math is complex and not entirely convincing.
>
> The position of Venus in the Earth's sky cycles in the
> time it takes Venus to lap the Earth in its orbit, 593.92
> Earth days, the synodic period. Oddly, that period is
> almost 5 Venus days, to be exact, 5.0014 Venus days.
> This means, annoyingly, that when you're trying to
> radar map Venus from the Earth at the close approach
> when you have the highest resolution, you're looking
> at almost exactly the same patch of Venus you were
> looking at the last time! Over and over again.
>
> The synodic period of Venus, 593.92 Earth days,
> is almost exactly 8/5ths of an Earth year, so that every
> eight Earth years the positions of Earth and Venus line
> up very closely with only a tiny amount of drift in position
> from cycle to cycle. Every 152 Venus synodic cycles of
> 593.92 Earth days, the line-up returns to its original
> precise positions, creating a long cycle of precise
> repetitions of the positions of Venus and the Earth.
> This long cycle takes 243.01 Earth years.
>
> Now, if the number 243.01 seems familiar, it's
> because it "happens" to be the length of Venus's axial
> rotation in Earth days, the sidereal period! The extreme
> regularity of this cycle of Venusian positions with respect
> to the Earth creates the long and precisely repeating
> cycle of Venus's transits of the Sun, meaningless except
> that these mark the timing of the Sun's passage across
> the nodes of the mutual plane of Earth's and Venus's orbits.
>
> So, how many 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" <cmb62 at columbus.rr.com>
> To: <meteorite-list at 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 don't work. Hey! Let's
>> try elephants !"
>>
>> Hannibal
>>
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Received on Thu 11 Jun 2009 06:22:16 PM PDT