Alaska's Being Followed by a Moon Shadow
If dusk falls early on March 8, 1997, blame the moon.
The orb that orbits us will throw its shadow over the earth that day. Just before sunset, the moon will intercept up to 70 percent of the sun's rays before they reach Alaska. People in Mongolia and southern Russia will experience a total solar eclipse.
We shouldn't need to dig out the flashlights here, but our partial solar eclipse may bug the birds, said Hans Nielsen, a professor of geophysics at the Geophysical Institute.
"I think it will be dark enough that the birds will think that it's evening and head for the nest," Nielsen said.
Occurring somewhere on Earth about every two years, total solar eclipses have been recorded since ancient time. As is recorded in the Chinese "Book of History," an eclipse on Oct. 22, 2136 B.C. surprised the Chinese. When the sky darkened, many assembled in panic to perform their usual eclipse rituals of shouting, beating drums, and shooting arrows into the sky to scare the dragon that was eating the sun. Pity the official court astronomers, Hsi and Ho. They were drinking rice wine at the time and failed to predict the eclipse. They were beheaded for their negligence.
The risks of drinking wine aren't so great for today's astronomers, who have calculated the dates of solar eclipses for the next few centuries. Solar eclipses occur only because of a neat coincidence--the moon, which is about 400 times smaller than the sun, happens to be about 400 times closer to the earth than the sun. When you finish with the calculations, the moon is just large enough to block out the sun and prevent direct sunlight from reaching the earth during a total solar eclipse.
Solar eclipses happen during a new moon, when the moon's orbit stations it between the earth and the sun. Eclipses don't happen during every new moon, which occur about every 29 days, because the plane of the moon's orbit around the earth is not the same as the plane of Earth's orbit around the sun. The shadow of the new moon is usually projected into space--either above the North Pole or below the South Pole.
On those days when the shadow does intersect with the earth, such as March 8, 1997, odd things happen here on the earth's surface. The moon's shadow--a disc with a diameter of 80 to 100 miles that travels at almost 3,000 miles per hour across the ground--cools the air below it from five to 10 degrees Celsius.
To view the partial solar eclipse from Alaska, Fred Espenak of NASA's Goddard Space Flight Center suggested using two sheets of cardboard. After poking a pinhole through one sheet of cardboard, hold it up so sunlight projects onto the other piece of cardboard. Although the image will be tiny, you can see the moon's shadow take a bite out of the sun. Throughout this procedure, of course, you should follow your mother's advice and avoid looking directly at our nearest star, which will damage your retinas despite the fact it's 93 million miles away.
Espenak said the March 8 partial eclipse over Alaska will start at about 4:30 p.m. and will last until sunset (which occurs at 6:20 p.m. in Fairbanks). It should be darkest as most of the moon shadow covers Alaska at about 5:30 p.m.
Although Alaskans will only experience a partial eclipse, the moon's path will cause a total eclipse over parts of Asia. Espenak, a man who has seen the sun go black a dozen times, is traveling to Mongolia to witness the total eclipse.
If you want to see a total eclipse without leaving Alaska, all you need is longevity and a ticket to Point Hope. Northwest Alaska will experience a total eclipse in March, 2033.
