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Saturday, February 16, 2008

Total Lunar Eclipse, Wednesday, February 20!

Don't miss this if you can help it! The last Total Lunar Eclipse visible from the United States until December of 2010 will take place on the evening of Wednesday, February 20! *

As this image* (taken from the official NASA page for this event) shows, the eclipse will be fully visible for most of the Western Hemisphere, and at least partially visible for everywhere but Australia, New Zealand, Eastern Russia, and most of Asia, including many of the islands of the Pacific.

For me, located snugly in the Eastern Time Zone, the Partial phase of the eclipse (when the Moon begins to move into the outer portion of the Earth's shadow, which exists because the Sun is an extended body in space, not a point source of light) will begin at 8:43 PM on the evening of Wednesday, February 20th. Totality (when the Moon moves entirely into the darker, inner portion of the Earth's shadow) will begin at 10:01 PM and end at 10:51 PM, with mid-eclipse at 10:26 PM. The Partial phase will end at 12:09 AM on the morning of Thursday, February 21st.

Those of you in other time zones can adjust the above numbers accordingly, or just check out the handy (but difficult to copy-and-paste!) table at NASA's page for this eclipse. Anyone in Europe hoping to catch a glimpse should remember that the eclipse will happen entirely after midnight, your time, so for you this will actually be a Thursday morning event.**

Things to watch out for:

The shadowed parts of the Moon are often much brighter at Totality than during the Partial phases! This is because the Earth has an atmosphere, and some of the sunlight that is blocked by the Earth (which appears much larger than the Sun in the Moon's sky)*** manages to sneak around the Earth by means of refraction through the atmosphere. From the Moon, the Earth would appear at Totality to suddenly be surrounded by a brightly glowing ring as the atmospere lights up - as many authors have put it, the Moon at Totality is lit up by the glow of every sunrise and sunset happening everywhere on Earth at that moment. But different atmospheric conditions of clouds, smoke, and volcanic dust cause the color of the Moon at Totality to vary from one eclipse to the next!

You can use a series of lunar eclipse observations to deduce that the Earth is a sphere! Notice that the edge of the Earth's shadow is round, regardless of how long ago the Sun set. That wouldn't happen if the Earth was flat - someone seeing the eclipse at sunrise or sunset would be seeing it through the "edge" of the flat Earth's shadow, which would appear like a line . The only shape that would always cast a round shadow is a sphere - or, at least, something sphere-like. In reality, Earth is an "oblate spheroid", slightly flattened at the poles and bulging at the equator.

Also, check out the stars around the Moon! That's something you don't see every day!...err, night. During one total eclipse many years ago, I was astonished by the sense of the three-dimensionality of the Moon, hanging like a purplish grapefruit against the distant stars.

...a very distant purplish grapefruit. How big do you think the Moon appears? The size of a dinner plate? A half-dollar? Grab a pencil with an eraser and hold it out at arm's length in front of the Moon. How do they compare?

Let's hope the weather cooperates, and we all have clear skies for viewing this amazing event! If you get pictures of it, let me know and I'll link to them!

*Yes, I know the image says "2008 Feb 21". They're using Coordinated Universal Time, which is the same as Greenwich Mean Time for our purposes. This event takes place in the early morning hours of Feb. 21, as far as Coordinated Universal Time is concerned.

**The Greenwich Mean Time figures are:
Partial phase begins 01:43 AM GMT
Totality begins 03:01 AM GMT
Mid-Totality 03:26 AM GMT
Totality ends 03:51 GMT
Partial phase ends 05:09 AM GMT

***The fact that the Moon and the Sun appear the same size in the Earth's sky is a remarkable and temporary coincidence - the Moon's orbit is gradually getting bigger, and in time it will be smaller than the Sun in Earth's sky, making Total Solar Eclipses a thing of the past.


Todd HellsKitchen said...

Thanks for telling me. I had no idea!

Kenny said...

I'm not sure whether to stay awake or get up early. I suspect the weather may dictate that. But the camera will be primed.

Gort said...

I hope it's clear and I will have my telescope out.

supertiff said...

and after all that, i'm thinking about that song 'total ecipse of the heart.'

what does that even mean, a total eclipse of the heart?

whimsicalnbrainpan said...

I hope the skies are clear. I missed the last one because it was cloudy.

There's something for you at my place.