IF there is a kind of music of the spheres, as Kepler suggested
centuries ago, it could be thought of as the accompaniment to
the solar system's stately cotillion of planets gliding around
the Sun, spinning and sometimes nodding, most with partners,
each responding in subtle ways to all the others. Orderly and
predictably harmonic this may seem, and in the short term it is,
but scientists analyzing the motions of planets with powerful
computers are realizing that there is a certain cacophony, as it
were, to the music of the spheres. In the new scientific
lexicon, the solar system is chaotic. This means that over great
spans of time an accumulation of small gravitational
disturbances from neighboring planets, combined with their own
slightly wobbly rotations, can cause significant fluctuations in
the orbits and orientations of the planets. The changes are
exponential, and this compounding effect leads to striking
consequences over time scales of four million years. Scientists
conclude that such behavior is ess