NASA发布的8月1日日食录像视频Solar Eclipse on August 1

Total Solar Eclipse on August 1: Where, How to See It

On August 1, 2008, a total solar eclipse will darken the skies across a narrow swath of Earth's Northern Hemisphere, seen as a blue line on the image above.

Starting around 8:30 a.m. Greenwich mean time, the eclipse will sweep across northern Canada into central Russia and Mongolia before ending in China.

The sun will be completely obscured for just under two and a half minutes, "a tad on the short side," according to astrophysicist Fred Espenak, an eclipse expert based at the NASA Goddard Space Flight Center.

A typical eclipse lasts for three minutes, Espenak said, and the longest possible is seven and a half minutes.

When it starts, this year's full eclipse will be visible from a narrow arc spanning the Northern Hemisphere.

Its path will begin in Canada and continue northeast across Greenland and the Arctic, then southeast through central Russia, Mongolia, and China.

The eclipse will start around 8:30 a.m. Greenwich mean time in the eastern part of the arc, leading to totality in just under an hour.

In a much wider swath of the globe—including northeastern North America along with most of Europe and Asia—people will be able to see a partial eclipse.

"Drop Dead Gorgeous"

The moon crosses between Earth and the sun once a month during the new moon. For an eclipse to happen, the moon has to come directly between the two bodies—it can't be too high or low relative to Earth. (See photos of the full moon from Earth and space.)

Sometimes the moon will be close enough that just an edge will pass in between, resulting in a partial eclipse.

About 25 percent of eclipses are total eclipses, and there are about seven of these a decade, Espenak said. But at any given geographic location, a total eclipse will be visible an average of once in 375 years.

The last total solar eclipse visible from the United States was in 1979, and it was seen mostly in the Pacific Northwest.

When a total solar eclipse takes place, about half the daytime world doesn't see any of it, Espenak said. Another 49 percent of people see it as a partial eclipse.
Less than one percent of people see totality, which Espenak describes as "drop dead gorgeous."

"On a scale of one to ten, a partial eclipse is of some interest," he said. "A total eclipse on that scale is ten million. It can't be compared to anything else. It should be on everybody's life list."

Of course, the weather can throw a monkey wrench in any observation plans.

This year, conditions in China are likely to be most favorable for getting a good look at the full eclipse, according to weather data analyzed by Espenak and Jay Anderson from the University of Manitoba in Canada.

Their calculations show that the skies above China in August are cloudy around 35 percent of the time, compared with upward of 90 percent of the time in many other parts of the eclipse's path.

"It's always a crapshoot," Espenak said. "You try to stack the odds in your favor."

Pop Tarts and Bad Omens

Tom Burns, director of the Perkins Observatory in Delaware, Ohio, helped put together a viewing-safety Web site during the Christmas eclipse of 2001.

He was hearing too often, he recalled, of people trying to view the partial eclipse through sunglasses, compact discs, or—surprisingly—Pop Tart bags.

"The only time it's safe to observe an eclipse through a Pop Tart bag is if the Pop Tart is still in it," he said.

He and his colleagues, who frequently instruct groups of sky-gazers on safe sun-watching, instead recommend special eclipse glasses.

Eclipses haven't always been eagerly anticipated, NASA's Espenak added. In ancient times the events were often seen as bad omens.

A total solar eclipse that may be tied to a real event was described in Homer's epic poem The Odyssey as spreading "an evil mist" over the world while suitors courted Odysseus's wife.

And an eclipse viewed in England in A.D. 1133 was seen as portending the death of King Henry I.

Even today, in some places, fears persist.

"A lot of … women believe viewing an eclipse will cause birth defects if they're pregnant," Espenak said. "I've seen this in Mexico, India, Indonesia, Bolivia."

For the growing population of sky-gazers who would love to see an eclipse and can't make it northward this year, it might be best to make reservations to visit southern Illinois, he added.

Weather permitting, people there will get to see total solar eclipses in 2017 and 2024.









There is more to know:
日食观测爱好者的盛宴 Greatest hits for eclipse fans
神秘的热带雨林  
侏罗纪时代 Jurassic
鸟瞰China: An Aerial View
维多利亚的秘密
美丽北极光  
看看真正的雪莲长什么样  
贵州乡村风光
水下精灵 Underwater Creatures