REVOLUTION OF THE EARTH
- 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.