Moon takes stage in a ballet with Earth's shadow Thursday
By Dan Vergano, USA TODAY
Clouds permitting, sky watchers in the Americas, Western Europe and Africa will enjoy a total lunar eclipse Thursday, one of nature's most compelling special effects. The partial lunar eclipse will start at 10:03 p.m. ET as the Earth blocks sunlight from the moon, gradually sliding into full eclipse at 11:14 p.m. ET. African and Euro-pean viewers will see the eclipse before or at dawn Friday.
In the USA, viewing will be best in the western and central states, but storm clouds and rain threaten elsewhere.
In Europe, skies should be clear over Spain, southern France and Italy, but clouds may impede viewing in the United Kingdom and from northern France to Germany. Mostly clear viewing is forecast for northern and southern Africa, but clouds and thunderstorms could block the view in central Africa.
The moon technically begins the eclipse about an hour before the partial eclipse phase, as the moon begins to pass into a region of half-shadow on the Earth's dark side called the penumbra.
During the total eclipse, the moon will pass entirely into the full shadow of the Earth, a region called the umbra, from the Latin word for shadow. It leaves it an hour later at 12:06 a.m. ET.
"You'll actually see the hard-edged shadow of the Earth as the total eclipse begins," says astronomer Fred Espenak of NASA's Goddard Space Flight Center in Greenbelt, Md. The partial eclipse ends at 1:17 a.m. ET. And the moon finally exits the penumbra about an hour later.
A faint red or gray glow will cover the moon during the total eclipse, making it still faintly visible. The glow comes from sunlight scattered off the edges of the Earth, which is bathed in light from the setting and rising sun, even as it places the moon in shadow.
Partial lunar eclipses occur when the moon passes only partway through the umbra region. The amount of dust in the Earth's atmosphere affects the size of the umbra and can throw off eclipse time predictions by a few moments, a measurement of some interest to atmospheric scientists.
Though lunar eclipses offer little scientific value to astronomers, Espenak says they are a powerful reminder of our place in the solar system. He maintains a Web site on eclipses at http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html.
The last total lunar eclipse took place in 2001; typically there are up to three every year.
Anyone who misses out on the event has a second chance this year. On Nov. 8, a total lunar eclipse is expected to be viewable from North and South America.
Two more should take place in 2004.