( CLASS - 6th ) CHAPTER - 4 The Motions of the Earth

1. What is rotation ? How much time does earth take in completing one rotation ?

Rotation – Rotation is the movement of the Earth on its axis from West to East.

                          It completes one round in about 24 hours.

2. What is meant by the revolution of the earth?

•Revolution – Revolution is the movement of the Earth around the Sun in a fixed path or orbit. 

3. What is a leap year?

A leap year is a year that has one extra day in it. A leap year occurs roughly every four years. Most years have 365 days, but a leap year has 366 days. The extra day is added onto the end of the shortest month, February; in a leap year, February has 29 days (instead of its usual 28 days). February 29 is called leap day.

4 .What is an equinox ? Which seasons are indicated by it in both the hemispheres ?

Equinox is the position of the Earth when the rays of the Sun fall directly on the Equator. At this position, neither of the Poles is tilted towards the Sun. As a result, the entire Earth has equal days and equal nights.

Vernal equinox and autumnal equinox seasons are indicated by it in both the hemispheres

5 .Why does the duration of day and night change in a year ?

The change between day and night is caused by the rotation of the earth on its axis. The changing lengths of days and nights depends on where you are on earth and time of year. Also daylight hours are affected by the tilt of the earth's axis is called Inclination of the earth’s axis  and it's path around the sun

1.Why are days & nights equal  on 21st March at all places on the earth ?Explain  

Days and nights are equal at all places on earth on March 21 because on this day sun rays will fall in the vertical direction towards the equator or at the center position of the earth. This supplies the equal light distribution from pole to pole which makes the day and night duration same.

2. Explain with the help of a diagram, why seasons are reversed between Northern and Southern Hemispheres.

Simply because of the tilt of the Earth.

Because of this inclination, the northern hemisphere, receives more energy from the Sun, While the southern hemisphere receives less.

This corresponds to the boreal summer (in the northern hemisphere) and the southern winter (in the southern hemisphere).

Six months later, It's the opposite because the southern hemisphere is better exposed to solar radiation.

In spring and autumn, the radiation received in the two hemispheres is identical. But the temperature is different, because a hemisphere coming out of winter and its soil and water have yet to be reheated, While the other hemisphere comes out of the summer and still enjoys its soil and water heat.

3. Why does the month of February have 29 days, after every four years ? Explain

The total duration of Earth's revolution around the sun is 365 days and 6 hours. After every four years the 6×4 hours i.e. 24 hour i.e. 1 day is added in the month of February. Such years are also known as leap years. They have 366 days.

Earth takes 365 days and 6 hours to complete one revolution around the sun. 

For a non leap year we count only 365 days and ignore the six hours. Those 6 hours keep getting added up every year and after 4 years become a day 6 hours multiplied by four= 24 hours which is one day. That day is 29th of February.

4. How do day and night occur on the earth ? Explain with the help of a diagram.

Day and night occur due to rotation of earth on its own axis. Part of earth which faces the sun ,experiences day.While part of earth away from Sun getting no light, experiences night. 

Earth is like a ball which spins as well as rotates around its axis.