These DAV Class 6 SST Notes and DAV Class 6 SST Chapter 4 Notes – The Motions of the Earth (Day-Night and Seasons) hold significant importance as study material for students.
The Motions of the Earth (Day-Night and Seasons) Class 6 DAV Notes
→ The earth is continuously spinning on its imaginary axis from west to east. It completes one round in about 24 hours. This motion of the earth is called rotation.
→ The earth also revolves around the sun in its fixed path or orbit. This motion of the earth is called revolution.
→ The earth’s axis is tittled to one side and makes an angle of 23%° from the vertical line. This tilt of the axis of the earth is called the inclination of the earth’s axis.
→ The rotation of the earth causes day and night. As the earth rotates, the day follows the night and the night follows the day turn by turn.
→ The revolution of the earth causes seasons. The earth takes 365% days or one year to complete one revolution around the sun. The year of 366 days is called a leap year.
→ There are four seasons in a year- summer, winter, spring and autumn. Seasons change due to the change in the position of the earth around the sun.
→ The rays of the sun are vertical at the Tropic of Cancer. Hence, these areas are extremely hot.
→ The Arctic Circle faces the sun for 24 hours. The region around the North Pole faces the sun for a period of about six months.
→ In the Northern Hemisphere the longest day and the shortest night occur on 21st June. In the Southern Hemisphere, the situation is just the opposite. The day is the shortest and night is the longest on this day. This position of the earth is called summer solstice.
→ In the Northern Hemisphere, the shortest day and the longest night occur on 22nd December. It is winter in this hemisphere. This position in the Northern Hemisphere is called winter solstice. In the Southern Hemisphere the longest day and the shortest night occur on 22nd December.
→ On 21st March, the duration of day and night becomes equal in both the hemispheres. Both the hemispheres receive equal amount of heat. It is spring in the Northern Hemisphere and is called vernal equinox.
→ Rotation: The movement of the earth on its exis.
→ Revolution: The movement of the earth around the sun in a fixed path or orbit.
→ Orbital plane:The plane formed by the orbit.
→ Leap year: The year in which February is of 29 days instead of 28 days.
→ Orbit: The earth revolves round the sun in its fixed path is called orbit.
→ Equinox: Equal night.
→ Axis : A line that joins the North Pole and South Pole about which the earth rotates.
→ Inclination : Degree of sloping.
→ Vertical rays : The rays which fall directly overhead. It covers minimum distance in the atmosphere.