saros or saros period

The length of one cycle of solar and lunar eclipses, at the end of which the pattern of eclipses recurs, except that the area on Earth from which an eclipse is visible will be about 120 degrees of terrestrial longitude to the west of the area where it was last observed.

One saros period is the amount of time required for the motions of the Earth and moon to carry the centers of the sun and moon back to almost exactly the same relative position. The saros period is 6,585.32 days or 18 years 11.33 days, or 233 lunations.

The interval was discovered by the Babylonians, but the name is more recent. In Babylonia, saros was the name of the number 3,600.

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