The reason is that while the earth blocks all sunlight from directly hitting the moon, the lower frequency red light bends and wraps around the earth and still hits the moon.
Tonight's total eclipse to color the moon
by John Stanley - Dec. 20, 2010 12:00 AM
The Arizona Republic
One of the best lunar eclipses in years will be visible - weather permitting - tonight.
Over the course of the 5 1/2-hour eclipse, the moon will grow gradually darker, turning colors that typically range from burnt orange to brick red to a lustrous umber, then slowly return to normal.
"What we're going to see is the moon slowly changing color as it passes through the shadow of the Earth," said Mike George, planetarium director for the Arizona Science Center.
Although the eclipse begins at 10:29 p.m., the moon won't look any different for 30 minutes or so, said Alan MacRobert, a senior editor at Sky & Telescope magazine. By midnight, the eclipse will be obvious.
Observing the curved shadow slicing across the moon is how the ancient Greeks deduced that the Earth is a sphere, MacRobert said.
The best part of the total lunar eclipse will be from 12:41 a.m. to 1:53 a.m., when the moon will be darkest, completely covered by the Earth's shadow. The moon's exact hue depends on global atmospheric conditions and is impossible to predict.
Since the southern, or bottom, part of the moon passes closer to the center of the Earth's shadow, it likely will be darker than the northern half, George said.
Special equipment isn't needed to observe a lunar eclipse, but binoculars or telescopes will help show the details.
"We go through most of our lives like ants in an anthill," MacRobert said. "We only see what is right around us. Astronomy prompts us ants to stop and look around at the enormously larger world we're all a part of."
The last total lunar eclipse in North America was almost three years ago, and it will be 2014 before the next one is visible across the United States.
Lunar science
A lunar eclipse occurs when the sun, Earth and moon align and the moon passes through the Earth's shadow. We don't see a lunar eclipse every month because the moon's orbit is slightly tilted with respect to the Earth.
If you'd like to do more than watch the eclipse, here are a couple of projects for amateur astronomers:
- John Westfall, a science editor with the Association of Lunar and Planetary Observers, is collecting naked-eye timing observations of the different stages of the eclipse.
Details: alpo-astronomy.org/eclipse/TLE21DEC10.html.
- You can record the times of the shadow crossing specific lunar craters and other surface features.
Details: skyandtelescope.com/cratertimings.
How a lunar eclipse helped Columbus' crew avoid hunger
February 1504 - Christopher Columbus was in a bad way.
In the course of his fourth visit to the New World, badly leaking ships left him stranded on what is now Jamaica.
The inhabitants, initially hospitable, had grown hostile at the crew's transgressions and had threatened to cut off the crew's food supply.
While consulting his ephemerides, charts that give the positions of astronomical objects at given times, Columbus realized that astronomers had predicted that a lunar eclipse would be visible in a couple of days.
The day before the eclipse, he told the local leaders that if they didn't change their minds, the moon would disappear from the sky.
They scoffed, but after the eclipse occurred, as predicted on Feb. 29, they relented.
Four months later, Columbus and his crew were rescued. He returned to Spain in November, never to return to the New World.
"The story sounds too good to be true," said Alan MacRobert, a senior editor at Sky & Telescope magazine. "But it really happened."
- John Stanley
Entire nation gets a 'ringside seat' to total lunar eclipse
By Elizabeth Weise, USA TODAY
If you step outside late tonight into early Tuesday morning, you may notice the moon looks like a luminous rotten orange. It's a total lunar eclipse that will be visible to everyone in North and Central America, including Alaska and Hawaii.
"We've all got a ringside seat to this one," says Alan MacRobert, editor of Sky & Telescope magazine. "We'll be watching it together."
During a lunar eclipse, the Earth lines up directly between the sun and the moon, so there is no direct sunlight to hit and reflect off the moon's surface. The only light that reaches it is "filtered and bending through our atmosphere," MacRobert says. That gives it the color of "all of the world's sunrises and sunsets" together.
The total eclipse will last for 72 minutes, a deeper "night within a night," as he puts it. The moon will be partially eclipsed for about an hour as it goes into and out of the Earth's shadow. The total eclipse will last from 2:41 to 3:53 a.m. ET.
"It's going to take a long time to watch the whole eclipse, about 3½ hours," says Rebecca Johnson, editor of StarDate magazine.
The color the moon takes on during the eclipse depends on what's in Earth's upper atmosphere, or stratosphere, says Fred Espenak, a scientist emeritus with NASA's Goddard Space Flight Center and eclipse specialist.
"Volcanoes throw up sulfur dioxide, and when that gets to the upper atmosphere in the stratosphere, it combines with water vapor, creating a smog of sulfuric acid that reddens the light even more. So the more volcanic activity you have on Earth, the more it darkens and reddens the eclipse."
Richard Keen, an atmospheric scientist at the University of Colorado-Boulder, says the stratosphere is fairly clear right now, so this eclipse will be pretty light, most likely bright red to bright orange. "So it will be very colorful," Espenak says.
Most places on Earth see total lunar eclipses every three to five years. They tend to "occur in clumps," Espenak says.
There will be three over the next 12 months: Tonight, June 15 and Dec. 10. The June eclipse won't be visible from North America, and next December's will be visible only in the western part of the continent. "But the one coming up is ideally situated for all of the United States," he says.
In past ages, "these things spooked the bejesus out of people before people understood what caused them," MacRobert says.
Today, science museums, parks, colleges and universities across the nation will be hosting viewing parties. Astronomers and telescopes will be on hand to explain what's happening and give the public a closer look into the awe-inspiring sight of the moon slowly disappearing from the sky.