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  1. #1
    Randy Ellig's Avatar
    Randy Ellig Guest

    Default Stability of Solar System

    How stable is our solar system?
    Where all the planets ,we have today,around
    4.5 billion years ago?
    I attended a public lecture awhile back in which the speaker(sorry can't
    recall his name) told us
    computer simulations of our solar system indicate
    that Mercury will be ejected from our system sometime in the distant future.
    This got me thinking about the distant past .
    I wonder how many planet's we started out with?
    Any thought's

  2. #2
    Sam Wormley's Avatar
    Sam Wormley Guest

    Default Stability of Solar System

    Randy Ellig wrote:

    The further back in time... the greater number of bodies.
    Have you a quantitative definition for planets?

  3. #3
    Olga Kulodnai's Avatar
    Olga Kulodnai Guest

    Default Stability of Solar System

    Must weigh more than a breadbox and last longer than RichA's attention

    Sam Wormley wrote:

  4. #4
    Uncle Bob's Avatar
    Uncle Bob Guest

    Default Stability of Solar System

    Randy Ellig wrote:

    From what I have read, the planet Mercury will be enveloped by the
    swelling red giant sun in about 1.6 billion years. The same model
    projects that Venus, Earth and Mars will be pushed away from the sun to
    approximate distances of 1, 2 and 3 AU respectively by a combination of
    increased solar winds and eventually the puffing off of the sun's
    "atmosphere" to form a planetary nebula, much like the Ring or Dumbell
    This all sounds very disturbing, but for some reason, I'm not worried
    about it in the least.

    We "started out" with no planets. There was a protoplanetary disc
    circling the sun early on. From this disk, some theories suggest,
    planets accreted by gravity. As their mass increased, the began sending
    smaller bodies whizzing all over the place. This created the earth's
    moon, by collision, then ruined it's showroom shine by bombardment.

    Gravity pretty much cleaned out the space between the planet's orbits
    over time. Outside the planet's orbits (which is to say, beyond
    Neptune's orbit), the Kuiper Belt remained, unaccreted debris from the
    early solar system. There, smaller objects sometimes collided, forming
    KBOs (Kuiper Belt Objects), of which, according to some, Pluto and it's
    moon Charon, and Quorar are two excellent examples.

    Even further out, and stretching to a distance of 3 light years or so,
    the Oort Cloud forms a spherical envelope of objects surrounding the
    solar system. Passing stars and tidal forces send some of these objects
    into the inner solar system, and we observe their passage as comets.

    Some KBOs are also seen as comets, but they can be distinguished by
    their relatively short periods and orbit directions. Generally they
    orbit the sun in the same direction as the planets. Not necessarily so
    with Oort Cloud objects.

    Science has yet to locate the planet Krypton, or explain how an infant
    from that world survived a journey in a chemical rocket that crashed on
    earth and grew up to become Superman. Funding for this kind of research
    is difficult to secure.

    Clear Skies,
    Uncle Bob

  5. #5
    Wally Anglesea™'s Avatar
    Wally Anglesea™ Guest

    Default Stability of Solar System

    On Thu, 26 May 2005 00:08:55 -0400, "Randy Ellig" <>

    OH my God! When? I need to get photographs! :-)

    There's no real way of knowing, but I'd suggest that the way we look
    now is pretty much it, that is, it would have only been smaller
    objects than Pluto that we lost.


    Find out about Australia's most dangerous Doomsday Cult:

    Astronomy pages:

    "You can't fool me, it's turtles all the way down."

  6. #6
    Bob May's Avatar
    Bob May Guest

    Default Stability of Solar System

    One of the things that you have to remember about computer simulations is
    that they are DIGITAL representations of what is happening. This means that
    the numbers put into the simulation are only approximations of reality.
    Sadly, slide rules are no longer used but if they were, people would be a
    lot more aware of the problems of approximations. With slide rules, the
    error band of what is the right answer becomes significant a lot faster than
    using a calculator.

    Why isn't there an Ozone Hole at the NORTH Pole?

  7. #7
    Chris L Peterson's Avatar
    Chris L Peterson Guest

    Default Stability of Solar System

    On Thu, 26 May 2005 00:08:55 -0400, "Randy Ellig" <>

    Strictly speaking, no body in the Solar System is in a stable orbit. The
    dynamics of the Solar System reflect metastability, and are chaotic.
    That said, the region of metastability is broad, and I don't believe
    that any calculation is possible that could predict the ejection of
    Mercury beyond a probabilistic solution. The situation is further
    complicated by the unpredictable interaction of planets with large
    objects occasionally entering the inner Solar System, either from
    interstellar space or from the Oort cloud. In the absence of such
    events, however, I have read that there is a high probability of the
    current planets still being here, and in similar orbits, when the Sun
    stops burning (the inner planets may be orbiting inside the enlarged Sun
    at some point, however).


    Chris L Peterson
    Cloudbait Observatory

  8. #8
    RichA's Avatar
    RichA Guest

    Default Stability of Solar System

    On Thu, 26 May 2005 04:38:43 GMT, Sam Wormley <>

    Anything larger and rounder than Pluto
    that doesn't orbit another planet.

  9. #9
    Tim Killian's Avatar
    Tim Killian Guest

    Default Stability of Solar System

    There are no computer models accurate enough to predict planetary
    motions/positions beyond a few hundred thousand years on either side of
    "right now". What happens in the distant future, or what transpired in
    the distant past is anybody's guess.

    Randy Ellig wrote:

  10. #10's Avatar Guest

    Default Stability of Solar System

    But if they are box-turtles then the stacking is stable. If they are
    snappers then the state is metastable. I wonder which it is


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