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No sense making a will. Just as well spend it all while there's still time. :-)

On 6/11/09, Peter Fogg  wrote:
>
>
> A force known as orbital chaos may cause our solar system to go haywire,
> leading to a possible collision between earth and Venus or Mars, according
> to a study released on Wednesday.
>
> The good news is that the likelihood of such a smash-up is small, around
> one-in-2500.
>
> And even if the planets did careen into one another, it would not happen
> before another 3.5 billion years.
>
> Indeed, there is a 99 per cent chance that the sun's posse of planets will
> continue to circle in an orderly pattern throughout the expected life span
> of our life-giving star, another five billion years, the study found.
>
> After that, the sun will likely expand into a red giant, engulfing earth and
> its other inner planets - Mercury, Venus and Mars - in the process.
>
> Astronomers have long been able to calculate the movement of planets with
> great accuracy hundreds, even thousands of years in advance. This is how
> eclipses have been predicted.
>
> But peering further into the future of celestial mechanics with exactitude
> is still beyond our reach, said Jacques Laskar, a researcher at the
> Observatoire de Paris and lead author of the study.
>
> "The most precise long term solutions for the orbital motion of the solar
> system are not valid over more than a few tens of millions of years," he
> said in an interview.
>
> Using powerful computers, Laskar and colleague Mickael Gastineau generated
> numerical simulations of orbital instability over the next five billion
> years.
>
> Unlike previous models, they took into account Albert Einstein's theory of
> general relativity. Over a short time span, this made little difference, but
> over the long haul it resulted in dramatically different orbital paths.
>
> The researchers looked at 2,501 possible scenarios, 25 of which ended with a
> severely disrupted solar system.
>
> "There is one scenario in which Mars passes very close to earth," 794
> kilometres to be exact, said Laskar.
>
> "When you come that close, it is almost the same as a collision because the
> planets get torn apart."
>
> Life on earth, if there still were any, would almost certainly cease to
> exist.
>
> To get a more fine-grained view of how this might unfold, Laskar and
> Gastineau ran an additional 200 computer models, slightly changing the path
> of Mars each time.
>
> All but five of them ended in a two-way collision involving the sun, earth,
> Mercury, Venus or Mars. A quarter of them saw earth smashed to pieces.
>
> The key to all the scenarios of extreme orbital chaos was the rock closest
> to the sun, found the study, published in the British journal Nature.
>
> "Mercury is the trigger, and would be the first planet to be destabilised
> because it has the smallest mass," explained Laskar.
>
> At some point Mercury's orbit would get into resonance with that of Jupiter,
> throwing the smaller orb even more out of kilter, he said.
>
> Once this happens, the so-called "angular momentum" from the much larger
> Jupiter would wreak havoc on the other inner planets' orbits too.
>
> "The simulations indicate that Mercury, in spite of its diminutive size,
> poses the greatest risk to our present order," noted University of
> California scientist Gregory Laughlin in a commentary, also published in
> Nature.
>  >
>

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