Photo of moon at right: ©2000 Fred Espenak for NASA.
About 500 years ago, a lunar eclipse saved Christopher
Columbus from the wrath of angry islanders.
Marooned on the sandy shores of Jamaica in 1503, the explorer and his crew depended on the hospitable natives for food and supplies. But, as we know from history books, Columbus wasn't always the gracious guest. Arrogant and rude, the explorer alienated the very people he relied on for survival.
As a result, the natives got restless and cut off all aid to the sailors. Columbus, of course, would not tolerate such actions. After consulting his almanac and sand glass, the navigator, who used the stars to guide him through oceans, knew that there'd soon be a lunar eclipse, which would cause the moon to vanish as it passed through the Earth's shadow.
"Columbus told the natives that if they did not cooperate he would confer with God and remove the moon from the sky," says Fred Espenak, a leading expert on eclipses and an astrophysicist at NASA's Goddard Space Flight Center in Maryland.
The natives thought Columbus was bluffing, but then they watched one of the brightest objects in the sky fade into the night. "They were terrified," tells Espenak. As with all lunar eclipses, the moon eventually reappeared. "When it came back, the locals repented and the supplies started flowing." About four months later, Columbus and his crew were rescued.
Tonight, Thurs., May 15, starting just after 10 p.m. EDT, the moon once again will disappear into the dark shadow of the Earth. It's the first total lunar eclipse visible from all of the United States since January 2000 and a great opportunity to witness the motion of our solar system. Pop outside and take a look. What you see could change your life, just as it had done for Columbus.
A lunar eclipse is born when two conditions mingle: the moon must be full, and it must pass through part of Earth's shadow. Photos by Leroy Sanchez, courtesy Los Alamos National Laboratory.
Total Lunacy
As long as the moon has circled the Earth and the
Earth has circled the sun, lunar eclipses have altered the evening sky.
On average, two occur each year, but not all are visible. One reason is
because only the nighttime half of the planet can view an eclipse - that's
barring bad weather, of course.
Here's what happens:
As the sun shines on the Earth, the Earth casts a shadow. This shadow is comprised of two parts: the penumbra, which is the outer part, and the umbra, which is the inner part and the darker of the two.
During a total lunar eclipse, the moon doesn't simply fade to black. In fact, it often takes on a reddish hue, ranging from peach to crimson. This has to do with the way the atmosphere scatters sunlight.
"The light that reaches the moon during a lunar eclipse is filtered and bent," explains Espenak. "Most of the blue light has been removed by the Earth's atmosphere." What remains is mostly red light, which reaches the moon and reflects back toward Earth. Without the Earth's atmosphere, the moon during a lunar eclipse would look like a lump of coal suspended in the night sky.
Because the atmosphere plays a role in what color the moon appears during an eclipse, the particles in the atmosphere also play a role. For instance, the volcanic ash that Mount Pinatubo spewed into the upper atmosphere in 1991 changed the color of the six lunar eclipses that followed. Some were so dark that the moon was nearly invisible. Despite the fact that more than 12,000 eclipses - both partial and total - will have occurred from 2,000 B.C. to 3,000 A.D. (Espenak has calculated the timing of them all), very few ever look alike.
Besides atmospheric conditions, the moon's path through the Earth's shadow also makes each one unique. During the total lunar eclipse of July 16, 2000, the moon was in the umbra for 1 hour and 47 minutes - the maximum duration possible. The one that happens tonight, Espenak predicts, will stay enshrouded in the umbra for about 53 minutes.
* =morning of May 16. EDT=Eastern Daylight Time,
CDT=Central Daylight Time, MDT=Mountain Daylight Time, PDT=Pacific Daylight
Time, GMT=Greenwich Mean Time, GMT +1 or 2=GMT + 1 or 2 hours.
Data from NASA/Goddard.
"The lunar eclipses are always different in one way or another," says Espenak, who has turned his hobby of photographing these celestial events into a life-long passion. "The colors are always a little unexpected."
The next total lunar eclipse visible from the United States will occur Nov. 8 of this year. The moon's time in the umbra will last only about 24 minutes. Regardless, Espenak says, "It is unusual to have these two total eclipses in one year. Usually, you have to wait several years to see another."
Moon-gazers may look forward to lunar eclipses so they can see the moon in a different light, but astronomers look forward to them so they can see stars in a different light. Because the moon is the second brightest object in the night sky, it outshines the fainter light from distant stars, which makes them difficult to study. Espenak says that when the moon is dimmer, such as during a total lunar eclipse, astronomers have a rare opportunity to examine stars in the absence of radiant moonlight.
The greatest value of eclipses, however, is as an educational tool that generates excitement among children and adults alike, says Espenak. Lunar eclipses, different from solar eclipses, are safe to view. And you don't need the Hubble Space Telescope, he adds. "You can watch [lunar eclipses] in your own backyard, without special equipment or even binoculars."
This time-lapse photograph series was shot during
a 1993 lunar eclipse. The faint red glow visible in the central image
was cast by sunlight refracted through Earth's dusty atmosphere. Photo:
NASA.
The sublime and beautiful
Espenak, nicknamed "Mr. Eclipse" for about 10 years
now, recalls the first time he saw a lunar eclipse. "I was 7 or 8 [years
old] and my family went to the drive-in. But, instead of watching the
movie, I watched the eclipse."
For him, the event is about the sublime and beautiful.
Watching a lunar eclipse, he says, "is an aesthetic type of activity." But ask him what makes it so aesthetic, and he'll answer: "That's like asking [someone] why a sunset or the 'Mona Lisa' is beautiful - it's in the eye of the beholder."
But not all people behold a lunar eclipse. Some shun it.
"In days gone by," says Mr. Eclipse, "they were omens of misfortune, the deaths of kings, famine, disease, petulance, the bad fates of warring factions."
The ancient aristocrat Thucydides, who recorded first-hand the events of the Peloponnesian War waged between Athens and Sparta from about 431 to 404 B.C., attributes the ultimate defeat of the Athenian army to a lunar eclipse. According to his account, a total eclipse occurred just as the Athenians were about to pull out after a two-year siege. The soldiers took the eclipse as a sign that they should stay. But, during the delay, enemies attacked their army and fleet, eventually destroying them. This loss, historians noted later, contributed significantly to the ultimate demise of Ancient Greek civilization.
Even today, lunar eclipses carry superstitious signs. Some people in Japan believe an eclipse indicates a disease on the moon and, to protect themselves, cover their drinking wells before the celestial event. In India, some people shut themselves in their homes to avoid the "bad rays" emitted during a lunar eclipse.
Such superstitions are held around the world, says Espenak, who often receives e-mails from individuals wary of eclipses and their power.
Why do lunar eclipses affect us so deeply?
A lunar eclipse, Espenak explains, places man in the
cosmos: "Normally, you can't see things happening in the sky because they
operate on long-time scales. But with an eclipse, you can see things change
in minutes. When you watch one, you feel a part of nature. You see the
mechanics of the solar system and perceive the motion of the heavens."
Perhaps this is why the Athenians lost the Peloponnesian War or why Columbus's trick on the islanders saved his own life. Tonight, as the moon once again enters the dark shadow of the Earth, maybe Sudden Acute Respiratory Syndrome will be wiped out or the war on terrorism will end. Who knows? Only the Earth's shadow.
-- Emily Carlson 
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