eclipse

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Passage of one astronomical body through the shadow of another. The term is usually used for solar and lunar eclipses. A solar eclipse occurs when the Moon is between the Earth and the Sun (which can happen only at new Moon), the Moon blocking the Sun's rays and casting a shadow on the Earth's surface. A lunar eclipse occurs when the Earth is between the Moon and the Sun (which can happen only at full Moon), the Earth blocking the Sun's rays and casting a shadow on the Moon's surface.

During a total solar eclipse the Moon appears to cover the Sun's disc completely, as viewed from a small region around the centre of the Moon's shadow. In this area day turns into night. A total solar eclipse can last up to 7.5 minutes, and the Sun's corona can be seen. Between two and five solar eclipses occur each year but each is visible only in the band of the Earth's surface traversed by the Moon's shadow. Away from the centre of the shadow, the solar eclipse is partial; sunlight reaches the Earth around the edge of the Moon. When the Moon is at its furthest from the Earth it does not completely cover the face of the Sun, leaving a ring of sunlight visible. This is an annular eclipse (from the Latin word annulus meaning ‘ring’).

Lunar eclipses can also be partial or total. Total lunar eclipses last for up to 100 minutes; the maximum number each year is three. A lunar eclipse is visible from the whole night-time hemisphere of the Earth.

The number of stripes changed frequently until around 1800. Red, white, and blue became the colours of liberty and an inspiration for other revolutionary flags around the world. Effective date: 19 February 1937. >>