1. Define rotation and revolution

Rotation is the movement of the earth on its axis. The earth takes 24 hours to complete one rotation. Revolution is the movement of the earth around the sun in its orbit. The earth takes 365 ¼ days to complete one revolution.

2. The earth takes about …………………….. hours to complete one rotation.

24

3. Define the circle of illumination

The circle that divides the day from night on the globe is called the circle of illumination.

4. Why the rotation of the earth is important for the existence of life on earth.

If the earth did not rotate, the portion of the earth facing the sun will always receive the warmth and the other portion will not receive any heat or light at all. As a result, it will be freezing cold in that portion whereas it will be too hot in the portion receiving light and life will not be possible in such conditions.

5. The earth takes 365 ¼ days to complete one …………………………..

Revolution

6. What is a leap year?

A leap year is a year with 366 days. The earth takes 365 ¼ days to complete one revolution. However, for the sake of convenience, we consider the year as consisting of only 365 days. The six hours that are not included in a year are added to make one day over a span of four years. This day is added to the month of February. Hence, every 4th year, February has 29 days.

7. The earth moves around the sun in an …………………………. orbit.

Elliptical

8. Name the four seasons

Summer, winter, spring and autumn

9. Why do we have seasons?

Seasons change due to the change in the position of the earth around the sun.

10. What is the shape of earth’s orbit?

Elliptical orbit

11. What is summer solstice?

Northern hemisphere is tilted towards the sun on 21st June. Summer solstice is the position of the earth on that day in which the day is the longest and the night is the shortest. On this day, the rays of the sun fall directly on the Tropic of Cancer.

In the Southern hemisphere, the summer solstice is on December 22. On this day, the rays of the sun fall directly on the Tropic of Capricorn and places in the Southern hemisphere have the longest day and the shortest night on December 22.

12. What is equinox?

On 21st March and 23rd September, the rays of the sun fall directly on the equator. On this day, the whole earth experiences days and nights of the same duration. This is called equinox.

13. Which are the two motions of the earth?

The two motions of the earth are rotation and revolution.

14. What is orbital plane?

The plane formed by the orbit is known as the orbital plane.

15. Why does Southern hemisphere experiences winter and summer in different times than that of the Northern hemisphere?

Southern hemisphere is tilted towards the sun on 22nd December. Hence it is summer in the Southern hemisphere. At that time, it is winter in the Northern hemisphere because it is away from the sun. But on 21st June, Northern hemisphere is tilted towards the sun and hence it is summer there. Therefore, when it is summer in the northern hemisphere it is winter in the southern hemisphere.

16. Why do poles experience about six months day and six months night?

When the Northern hemisphere is tilted towards the sun, the North Pole receives light for the whole of the day. This position remains the same for 6 months.
In the Southern hemisphere, the South Pole does not get light during these 6 months. Hence, it experiences night for 6 months.