Skywatchers in the United States are preparing for a spectacular eclipse in their country's 241-year history. A total solar eclipse will sweep across the nation today, from Oregon on the west coast to South Carolina on the eastern seaboard.<br/><br/>It is the first such eclipse to make landfall exclusively in the US since the country's independence in 1776. Total solar eclipses see the Moon slip between the Earth and the Sun. The Moon's diameter appears to be the same size as that of our star and so blocks out its light. A giant shadow cast by this occultation then races across the surface of the Earth, plunging locations into darkness for a couple of minutes or more.<br/><br/>Those not directly under the Moon's shadow get to experience a partial eclipse which on this occasion will encompass all of North America and northern parts of South America. There are even parts of western Europe, including the UK and Ireland, that will snatch a sight of the Moon's disc taking a bite out of the Sun just as it sets.