How Solar Eclipses occur

A Solar Eclipse, the apparent Transit (passage) of our gravity-tethered Moon across the face of our Sun (as viewed by us from Earth), is a relatively common celestial phenomenon, and occurs in 3 main forms: Partial, Annular & Total.

During a Total Solar Eclipse, the oval/circular/then oval again totally dark total shadow (umbra) of the moon (up to 150 miles wide) cast upon Earth’s surface, races from west sinuously eastwards at a speed varying from about 1,200 to 4,000 mph, with a path length up to almost 9,000 miles.  Around this racing dark total shadow, a vast area of Earth’s surface thousands of miles across is subjected to the similarly racing partial shadow of our Moon--the penumbra.


Solar eclipses occur on average just less than once a year, with only some of them being Total.  Of these, many spend two-thirds of their duration casting their shadow only over the oceans or the polar regions, and only touch land briefly, such that they are generally only directly experienced by a very limited number of people.