watching as the moon blocks out the light from the sun, it can be hard to imagine the amazing cosmic coincidence taking place. the diameter is some 400 times larger than the moon's. for a couple of minutes when the sun and moon are perfectly aligned, the moon completely covers the sun's disk. the sun's atmosphere can be seen in the dim light with stars and planets. this glowing atmosphere is much hotter than the surface of the sun, but no one is sure why. it's a question puzzling astronomers. this so-called totality exists in a narrow band when the moon's shadow falls on the earth. outside the zone, some can see a partial eclipse, where it looks