Movement of the earth in its orbit around the sun. It’s in anticlockwise direction. The orbit of the earth’s revolution is elliptical. Takes 365 ¼ days in a year or 366 days in a leap year (every 4 years). The sun moves from the tropic of cancer to the equator and then towards tropic of Capricorn and back to the tropic of cancer. 21st march and 23rd September are called equinoxes because the length of day and night is equal.
The sun is vertically overhead at noon at the equator. 21st June is called summer solstice because its summer in the N hemisphere. The sun is vertically overhead at noon at the tropic of cancer. 22nd December is called winter solstice because its winter in the S. hemisphere. The sun is vertically overhead at noon at noon at the tropic of Capricorn. Solstice is the period of maximum tilting of the earth towards the sun.
Effects of the Revolution of the earth
- Causes the four seasons summer, autumn, winter and spring due to the movement of overhead sun causing changes in the heat belt.
- Causes variation of day and night’s lengths due to the earth’s axis being inclined to the path of revolution at an angle of 60◦.
- Equinoxes have equal lengths of day and night.
- Summers have longer days and shorter nights.
- Winters have longer nights and shorter days.
- Causes changes in the altitude of the midday sun due to the earth’s orbit being elliptical.
- Highest altitude during equinox
- Lowest altitude during solstices
- Causes lunar eclipse due to revolution bringing the earth in line with the sun and the moon.
PROBLEMS ENCOUNTERED IN FIELD WORK