Total Lunar Eclipse – December 20, 2010

Seth Jarvis

If you are awake between 11:30 PM (Mountain Time) Monday night  December 21 and 3:30 AM Tuesday morning  the 21st), and your skies are clear, step outside and have a gander at a celestial wonder.

 The Moon will be passing through Earth’s shadow during those hours and people on the night-time side of Earth will be treated to the sight of a Total Lunar Eclipse.

 When the Moon enters Earth’s umbra (the portion of the shadow that covers 100% of the Moon, shown as the inner of the two circles in the attached jpeg images) the Moon will turn a dark blood red.  That color is the result of sunlight on the opposite side of the world filtering through our atmosphere and refracting around Earth to escape past our planet to fall onto the Moon.  That reddened light is then being reflected back to us.

At about 11:30 PM (Mountain) the Moon begins to enter the "penumbra," the region of Earth's shadow that completely blocks sunlight.

At about 11:30 PM (Mountain) the Moon is fully within the punumbra (the region of partial shadow) and begins to enter the umbra, the region of Earth's shadow that completely blocks sunlight.

 

 

 

 

 

 

 

 

 

 

 

 

By 12:30 AM, the Moon is fully within the umbra, and the only sunlight reaching the Moon is light that has passed through Earth's atmosphere.

By 12:30 AM, the Moon is fully within the umbra, and the only sunlight reaching the Moon is light that has passed through Earth's atmosphere.

 

 

 

 

 

 

 

 

 

 

 

 

At about 3:00 AM, the Moon begins to emerge from the umbra, and gradually receives direct sunlight.

At about 2:30 AM the Moon begins to emerge from the umbra and transit through the penumbra, and gradually begins to receive direct sunlight.

 

 

 

 

 

 

 

 

 

 

 

 

By about 3AM, the show's over. Even though the Moon is still in Earth's penumbra, it will look about as bright as it normally does during Full Moon.

By about 3AM, the show's over. Even though the Moon is still in Earth's penumbra, it will look about as bright as it normally does during Full Moon.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

If the New Moon and Full Moon are caused by the Sun, Earth and Moon lining up once every orbit  of the Moon around Earth, then why aren’t there a solar and lunar eclipse every month?

The reason is because the Moon’s orbit is tilted slightly relative to Earth’s orbit around the Sun. Most of the time Earth’s shadow is a little above or below the Moon.

In ancient times the darkening and reddening of the Moon during an eclipse was thought to be due to a celestial monster devouring it.  Sacrifices, bonfires and loud noises were (and in some remote places, still are) employed to chase away the ravenous beast.  Fortunately, these “scare away the dragon” techniques always work!  After a couple of hours the Moon would always recover and go about its business in the heavens.

In 1504 Christopher Columbus, on his fourth voyage of exploration in the New World, found himself and his crew stranded in St. Ann’s Bay, Jamaica, his ships having been too badly damaged by wood worms and storms to continue his voyage.

The locals had been supporting Columbus and his crew for over a year while they awaited rescue, and the feeling was that their guests had over-stayed their welcome.  They wanted Columbus and his ill-mannered crew to leave.

Columbus consulted his shipboard ephemeris (tables of astronomical phenomena and their positions in the sky) and found that in the early evening on February 29th a total lunar eclipse would be visible from their location.

Calling the tribal leaders to a meeting, Columbus threatened that if he and his crew were not supplied with provisions, then he would cause the Moon to disappear from the sky.  The locals would have certainly had previous experiences with eclipses, but for someone to claim to be able to control such a thing would have to be pretty impressive.  Right on schedule, the Moon began to darken and turn red. 

“Columbus and the Lunar Eclipse” from Astronomie Populaire (1879) by Camille Flammarion

“Columbus and the Lunar Eclipse” from Astronomie Populaire (1879) by Camille Flammarion

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The tribal elders pleaded with Columbus to restore the Moon.  Columbus said he’d need to think about it, and retreated to his hut – knowing that he had about an hour to wait.  On schedule, Columbus came out of his hut and announced that so long as he and his crew were kept provisioned with food and other necessities for a while longer, he’d be willing to restore the Moon.  The deal was struck and, ta-da!  the Moon emerged from shadow and all was well.  Columbus and his crew were rescued later that summer.

The last time a total lunar eclipse was visible from the western U.S. was February 20, 2008.  If for some reason you can’t see the eclipse this Monday night then you’ll just have to be patient – the next total Lunar Eclipse you will be able to see from Utah won’t be until April 14, 2014.

Keep your fingers crossed for clear skies!

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