ECLIPSES

ECLIPSES
The total or partial obscuration of light from a celestial body as it passes through the shadow of another body is known as eclipse. On earth we are familiar with the solar and lunar eclipses. The moon, as a satellite of the earth, revolves round it; in the process it is bound to come in- between the sun and the earth at times. When both sun and moon are on the same side of the earth (i.e., in conjunction) so that all three bodies lie approximately on a straight line, the possibility exists for an eclipse of the sun, or solar eclipse.

It is a rare occurrence because the moon is so small and the plane of its orbit is tilted about 5° with respect to the plane of the ecliptic. It is for this reason that eclipses do not occur every month.' (Ectiptic is the apparent track of the sun throughout the year as a result of the earth's motion around it. The plane of the ecliptic is the plane passing through this path coincident with the place of the earth's orbit, and is imagined to be horizontal, passing through the globe's centre.) }Vhen the moon and sun are on the opposite sides of the earth (Le., in opposition), the possibility exists for an eclipse of the moon, or lunar eclipse. In this case the earth's shadow falls on the moon partly or completely covering it for a short while.

A solar eclipse occurs between sunrise and sunset at new moon; a lunar eclipse occurs at full moon. The chances of our seeing a lunar eclipse from a given place on earth are much better than for seeing a solar eclipse. In one year, up to se:ven eclipses can occur; either five solar and two lunar, or four solar and three lunar.
Incidentally, in a solar eclipse, the shadow of the moon
is some 45 km wide and crosses a belt of the earth several kilometres long.

In a lunar eclipse the earth's shadow is far larger than the moon and can cover the moon's surface for about 3 hours. A total lunar eclipse may last up to 1 hour 40 minutes. The moon does not become completely dark during most lunar eclipses. In many cases, it becomes reddish. The earth's atmosphere bends part of the sun's light around the earth and towards the moon.' This light is red because the atmosphere scatters the other colours present in sunlight in greater amounts than it does red, In the case of a total solar eclipse, the totally darkened period may be as long as 7 minutes and 40 seconds, but the average is about 2Vz minutes. The path of totality is wide but not wider than about 274 kilometres.