(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...
Question 1 Report
(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 suitable diagram describe an eclipse of the sun
Answer Details
(a) Distinction between rotation and revolution of the earth
| Rotation | Revolution |
|---|---|
| It is the spinning of the earth on its own axis. | It is the movement of the earth in its orbit around the sun. |
| The earth turns from west to east. | The earth travels along an elliptical path round the sun. |
| One complete rotation takes about 24 hours (one day). | One complete revolution takes about 365¼ days (one year). |
| It is a movement about the earth’s axis. | It is a movement along the earth’s orbit round the sun. |
| It causes day and night. | It causes the seasons and the varying length of day and night. |
(b) Two effects of the rotation of the earth
- 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.
- 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.
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