Planet Orbit

When is the next planetary alignment?

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What will happen if there is a series of planetary alignments. Will the earth tilt over? No. Will tidal forces trigger earthquakes? No. Will the polar ice caps melt? No. Will you even be able to see the alignments? Not really.

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Several planets are assembling toward a rare alignment in April 2002, when five of them will crowd into a patch of sky small enough that all will be visible in a single glance. The setup will provide a planet-watching opportunity that won't be repeated for a century.

www.space.com

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If several planets are orbiting the sun at known speeds and current positions, how many years will it be before those planets are perfectly aligned? This is a frequently asked question, but it's a bit tricky, because it involves the issue gravitational harmonics, which tend to force the periods of the planetary orbits to be rational multiples of each other. However, setting this aside, and assuming arbitrary real constants for the periods of the planets, the answer is that - except in very special cases - the planets will never be perfectly aligned (assuming we have more than two planets).

www.mathpages.com

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Given that the solar system has been around for several billion years, the odds are that the planets have been reasonably well lined up any number of times.

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