(a) Distinguish between rotation and revolution of the earth (b) Highlight any two effects of either rotation or revolution of the earth (c) With the aid of...

(a) Distinction between rotation and revolution of the earth

(b) Two effects of the rotation of the earth

1. Alternation of day and night: as the earth spins on its axis, the half facing the sun experiences day while the half turned away experiences night, and the two alternate every 24 hours.
2. Deflection of winds and ocean currents (Coriolis effect): the earth’s rotation deflects moving winds and ocean currents (to the right in the Northern Hemisphere and to the left in the Southern Hemisphere) and also produces the difference in local time between places on different meridians.

(c) An eclipse of the sun (solar eclipse)

An eclipse of the sun occurs when the Moon comes exactly between the Sun and the Earth, so that the three bodies lie in a straight line and the Moon’s shadow falls on the Earth, cutting off the sun’s light from part of the earth’s surface. It can happen only at new moon.

Because the Moon is much smaller than the Sun, its shadow has two parts. The dark, cone-shaped inner shadow is the umbra; where its tip touches the earth the sun is completely hidden and observers there see a total eclipse. Surrounding it is the lighter shadow, the penumbra; places within it see only part of the sun covered, giving a partial eclipse. As the Earth rotates and the Moon moves in its orbit, the shadow sweeps across the earth, so the eclipse lasts only a short time at any one place.