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16739Fwd = The cosmic timebomb

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  • Frits Westra
    Apr 1, 2004
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      The Independent


      The cosmic timebomb

      The asteroid that wiped out the dinosaurs was thrown to Earth in a moment
      of 'planetary madness'. And scientists can now predict when the heavens
      will go haywire again, says Marcus Chown
      31 March 2004

      There's something badly wrong with the pendulum clock in the corner of the
      room. Normally, it ticks rhythmically, its bob swinging back and forth
      with hypnotic regularity. Over time, however, the size of the swing
      gradually gets larger, the ticks louder and louder. And, very occasionally
      - in fact, so occasionally that nobody has yet ever observed it - the
      clock goes stark-staring mad, ticking completely erratically as the
      pendulum bob swings first to one side, then twice or three times as far to
      the other side.

      Surely, there is no clock that behaves like this? According to a team of
      geophysicists and mathematicians, there is: the clock in the sky. "For
      tens of millions of years, the planets circle the Sun with the
      predictability of clockwork," says Michael Ghil of the Ecole Normale
      Supérieure in Paris and the University of California at Los Angeles
      (UCLA). "Then, without the slightest warning, everything goes utterly

      The heavens are generally considered to be a paragon of predictability so
      this is a radical stuff. But it is only the beginning. Ghil and his
      colleagues, Ferenc Varadi and Bruce Runnegar at UCLA, believe the last
      time the solar system went insane was roughly 65 million years ago. "It
      seems too much of a coincidence," says Ghil. "We think it may have been
      connected with the extinction of the dinosaurs."

      The kind of planetary madness Ghil and his colleagues are talking about
      goes by the name of "chaos". Chaos is defined as erratic motion with no
      sign of any regularity. Loosely speaking, chaotic systems are infinitely
      sensitive to initial conditions, like a hurricane in the Caribbean that
      was triggered by the flutter of a butterfly's wings in distant Hawaii.

      In the solar system, the most important drivers of chaos are Jupiter and
      Saturn because they are the most massive of the planets. In their
      investigation of planetary chaos, it is therefore these two planets that
      Ghil and his colleagues have focused their attention on. The
      Jupiter-Saturn system is actually not inherently chaotic. However, it is
      known to skate close to the edge of chaos. The possibility therefore
      exists that, occasionally, something might cause it to teeter over the
      edge into planetary insanity.

      --[snipped -- full story at above URL]-----

      © 2003 Independent Digital (UK) Ltd