Step outside on a sunny day, look down and examine your shadow. It's dark in the middle, pale and fuzzy around the edges, and it always points away from the sun.
Although we seldom see it, Earth has a shadow, too, much like your own: dark inside, pale outside, pointing away from the sun. Way away. Earth's shadow stretches almost a million miles into space, far enough to reach the moon.
On Saturday, Nov. 8th, the full moon will glide through our planet's shadow. Observers on every continent except Australia can see the event, which astronomers call a lunar eclipse.
Right: Frank Reddy of Celestial Delights created this animation of the upcoming lunar eclipse.
Sky watchers will first notice a shadowy darkness creeping over the moon's northeastern limb at 23:32 Universal Time (UT) on Nov. 8th. Watching Earth's shadow sweep across the moon's terrain is fun. Even better is totality, when the entire moon is covered in shadow. Totality begins at 01:06 UT on Nov. 9th and lasts for 25 minutes. (Note: the table below converts UT to US standard time zones.)
The totally eclipsed moon won't be totally dark--and that's what makes totality delightful. Earth's atmosphere bends sunlight into our planet's shadow and onto the moon. This sunlight is reddened as it travels a great distance through our dusty atmosphere, and so the moon looks red. Sunsets on Earth look red for the same reason.
Above: Times printed in light gray denote events that happen before local moonrise, which on Nov. 8th will be between 4:45 p.m. and 5:00 p.m. for most observers. So, e.g., almost none of the eclipse will be visible from Hawaii; all of it will be visible from the Eastern time zone.
This is the second lunar eclipse of 2003. Observers of the first one in May might remember that the moon was nearly invisible during totality. This eclipse will be different. During totality on Nov. 8/9th the moon will remain relatively bright, and there will be a pleasing gradient of color across the face of the moon--pale-white on one side, crimson-red on the other.
Why the difference? It has to do with the structure of Earth's shadow and where the moon glides through it.
Earth's shadow is shaped like a cone with two parts. The umbra (on the inside) is dark while the penumbra (on the outside) is pale. Remember your personal shadow? It has these parts, too. The umbra is where the sun's light is completely blocked. The penumbra, that pale fringe around the umbra, is where the sun's light is only partially blocked.
Lunar eclipses are considered total when the moon passes completely into Earth's umbral shadow. In May 2003 the moon passed close to the middle of the umbra. The eclipse was therefore long (52 minutes of totality) and dark. In November 2003 the moon will merely skim the umbra, producing an eclipse that's shorter (25 minutes of totality) and brighter.
Right: Earth's cone-shaped shadow and the moon's path through it on Nov. 8th and 9th, 2003.
The total phase on Nov. 9th lasts from 01:06 UT until 01:31 UT. Then Earth's shadow will begin to recede, and by 03:04 UT it will all be over, the shadow gone, the glaring full moon back to normal.
People in Europe and western Africa will be able to watch the entire eclipse. For them it occurs while the moon is high in the night sky. North Americans near the Atlantic Ocean will also have a splendid view. North Americans on the Pacific side of the continent, however, are going to see just the last half of the event; the first half happens before moonrise. Even half an eclipse is worth watching, though. And just in case you're wondering what this lunar eclipse might look like from the moon, read the short science fiction story "Lunar Eclipse 2105" from Science@NASA.
For more information about this eclipse and others please visit NASA's Eclipse Home Page.
Eclipsed Moon Montage -- from Astronomy Picture of the Day
Lunar eclipse photo gallery -- from SpaceWeather.com
Lunar Eclipse Visibility Map -- from NASA
What is UT? Universal Time. Eclipse times in this article are given in terms of UT. If you need help translating that to your local time zone, visit time.gov or check the US Naval Observatory's standard time zone conversions.