[Gk. ekleipsis, a failing.] When a body which does not allow light to pass through it (an opaque body) is exposed to the light of the sun or of any other luminous body it casts a shadow behind. An eclipse of the moon is caused by the moon entering the shadow of the earth ; which can only happen at the time of full moon, when the earth lies directly between the sun and moon. An eclipse of the sun takes place when the moon, coming between the earth and the sun, intercepts the sun's light. This can only happen at the time of new moon, when the moon comes directly between the sun and the earth. Usually the moon hides the whole disc of the sun, producing a total eclipse; but occasionally a thin band of sunlight is visible round the edge of the moon, and then we have what is known as an annular eclipse (annulus, a ring). This is because the moon is not always at the same distance from the earth when the eclipse happens, and at its greatest distance the apparent size of the moon is less than that of the sun. If the moon is a little out of the central line between the earth and sun a partial eclipse is produced.
ECLIPSE OF THE SUN.