What is a total solar eclipse?

A total solar eclipse occurs when the disk of the moon appears to completely cover the disk of the sun in the sky. The moon orbits an average of 239,000 miles (385,000 kilometers) from Earth — just the right distance to seem the same size in the sky as the much-larger sun.

During a total solar eclipse, the disk of the moon blocks out the last sliver of light from the sun, and the sun's outer atmosphere, the corona, becomes visible. The corona is far from an indistinct haze; sky-watchers report seeing great jets and ribbons of light, twisting and curling out into the sky.

During totality, the area inside the moon's shadow is cloaked in twilight. Just before and just after totality, observers can see this cloak of darkness moving toward them across the landscape, and then moving away.