9) Eclipse time limits

Columbus knew that lunar eclipses don't go on forever. Astronomers say none can last more than 3 hours and 40 minutes. Totality cannot run more than 1 hour and 40 minutes.

The period of totality for the Nov. 8-9 eclipse will be just 25 minutes.

An eclipse on May 4, 2004 -- best visible in Europe -- will have a period of totality of 1 hour and 16 minutes.

Why the difference? Earth's shadow is cone-shaped. Envision a slice of it, a two-dimensional circle through which the Moon can pass. Longer stretches of totality mean the Moon is traversing the center of the circle. Shorter total eclipses occur when the Moon's path is nearer the top or the bottom of the shadow.

Eclipse Overview | Minute-by-Minute Guide | All about the Moon

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