Eclipses take place because the Earth revolves around the sun and the moon revolves around the Earth. As the two bodies revolve counter clockwise, at some point the moon passes in front of the sun.

The size and distance of the moon and sun are such that they both appear the same size in the sky. When the sun passes behind the moon it is briefly blotted out entirely.

A solar eclipse occurs at the start of the moon's new phase. An eclipse of the moon occurs when the moon passes into the shadow of the Earth at the moon's full phase.

When the moon passes between the Earth and the sun, it casts its shadow on the Earth's surface. Those people in the shadow are the ones who see all or part of the sun disappear.

But because the shadow of the moon moves across the Earth so quickly (roughly 1,700 kph or 1,054 mph), a total eclipse never lasts longer than a few minutes.

The moon's shadow is 3,700 km (2,294 miles) across. Only within the very central region of this shadow, called the umbra, does a total eclipse occur.

In outer section of the shadow, called the penumbra, the eclipse is a partial one.

The further out in the penumbra that the eclipse is viewed the less the sun is obscured.

Although a total eclipse occurs somewhere on Earth every couple of years, to see one is quite rare because the umbral shadow is relatively small, and never any wider than 270 km (167 miles). The width of the umbral shadow for this eclipse is roughly 150 km (93 miles) in diameter.
 

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