Newspaper article The Christian Science Monitor

What Can You Learn from Watching a Lunar Eclipse?

Newspaper article The Christian Science Monitor

What Can You Learn from Watching a Lunar Eclipse?

Article excerpt

The Oct. 8 lunar eclipse has stargazers giddy with anticipation, because it promises a seemingly impossible view of both the eclipsed moon and the rising sun at the same time. But since the days of the ancient Greeks, astronomers have revered lunar eclipses of all kinds as keys to some of the mysteries of the solar system.

A lunar eclipse occurs when the sun, the Earth, and the moon fall into alignment so that the Earth's shadow obscures the moon. The phenomenon is one of the solar system's many tricks of light and shadow that have fascinated people for millenniums. Some ancients regarded the disappearance of the moon with fear and trepidation; others saw it as a cause for ritualistic celebration. Classical Greek philosophers, as was their custom, took a more analytical approach.

Proof that the Earth is roundContrary to popular belief, Christopher Columbus was not the first to suggest that the Earth was round. One of the first recorded arguments for a spherical earth comes from Aristotle - nearly 2,000 years before Columbus - says University of Puget Sound science historian James Evans.

"He mentions in his book 'On the Heavens,' that during an eclipse of the moon, you see the shadow of the Earth falling on the moon and it always looks circular in shape," Professor Evans explains. "He offered other arguments, but that's a pretty good argument right there."

Like many of the ancient Greeks' models, Aristotle's theory has held up only in part. Today, we know that that Earth is not a perfect sphere but is an oblate spheroid, with a heavier concentration of mass around the equator than at the poles, as proposed by Isaac Newton in the late 17th century.

A key to the day and night skyAncient Greek astronomers relied on the lunar eclipse to compare the nighttime and daytime sky.

"One of the ways that the ancients used to measure the longitudes of the stars would be to measure how far a star is from the middle of the moon in degrees during the middle of the eclipse of the moon," Evans says.

While the position of the sun is not visible at night, it can be easily determined during an eclipse when the moon is diametrically opposite the sun, Evans explains. …

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