Earth (Diameter: 12,756 km) moves around the Sun (Speed: about 30 km/sec) approximately once every 365 days. Moon (Diameter: 3,476 km) - which is about 385,000 km away from the Earth - moves around the Earth - approximately once every 29 days (Speed: about 1 km/sec).

These two motions - the motion of the Earth around the Sun and the motion of the Moon around the Earth - bring the Moon in between the Sun and the Earth - approximately once every 29 days. This is when we get the New Moon (i.e half of the Moon receiving the Sun's light is hidden from Earth and the portion of the Moon that doesn't receive the Sun's light is facing the Earth). Every year - there are 12 such occasions - once every lunar month.

Occasionally (at least twice a year) - the Moon comes just about exactly in between the Sun and the Earth, blocking the Sun (as viewed from the Earth). Depending on how much of the Sun is blocked, we get a total solar eclipse (Sun will be entirely covered by the Moon) or a partial solar eclipse (part of the Sun is covered by the Moon).

When the Moon comes in between the Sun and the Earth, it creates two types of shadows - the dark shadow, Umbra and the light shadow, Penumbra. The regions on Earth where Umbra falls will get to see a Total Eclipse and the regions on Earth where Penumbra falls will get to see a Partial Eclipse. Sometimes, the Earth may wholly pass through the Penumbra only (because of its orbit around Sun) - resulting in just a Partial Eclipse everywhere.

On rare occasions, another kind of Solar Eclipse also takes place. Because of its elliptic orbit, sometime during its orbit, the Moon gets closer to Sun than the normal (up to 13% away from the Earth than the average) - causing another shadow called the Antumbra. At these times, the Moon would look much smaller than the Sun. When an eclipse occurs now, the Moon will not block the Sun completely. It would appear to be inside the Sun. This is called the Annular Solar Eclipse.

Total Solar Eclipses are such spectacular occasions - viewable only at certain part of earth everytime such an eclipse occurs - people travel miles across the seas to view it! Upcoming solar eclipses are on March 19, 2007 (Partial), September 11, 2007 (Partial), February 7, 2008 (Annular), August 1, 2008 (Total), January 26, 2009 (Annular), July 22, 2009 (Total), January 15, 2010 (Annular) and July 11, 2010 (Total). Depending on time of the day and the viewing location, these eclipses will be visible or not visible from Earth.