Motions of the Earth
Summary
What cause the sun to rise in the east, and then later set in the west each day?Thisis because her Earth moving on its Axis. Apart from this movement the Earth also moves around the sun.Let us discuss about both movements.
1. Rotation of the Earth
When earth spins rotates around its axis, that movement of spinning is called rotation. The Earth rotates from the west towards east. It takes 24 hours or one day to make a complete rotation on its Axis. The Earth rotates about an imaginary line that passes through the North and South poles of the planet. This line is called the axis.
• Japan is known as Land of Rising Sun.This is because as it is located at the extreme east of the planet. So, it is said that the Sun first rises in Japan.
• Formation Day and Night The rotation of Earth produces the pattern of a night as different part of the Earth areexposed to sunlight. The Sun is always shining on one-half of the Earth. This is called day. The part of the Earth not facing the sun is in darkness, or night. So, we can say that day and night are caused by the rotation of the Earth. If there had been no rotation of the earth; one half of the earth would have been constantly in daylight and other the half would have been constantlyin dark. The portion under sunlight would have been too hot. On the other hand, the portion in dark would have been freezing cold. Such extremes of temperature could have made it impossible for life to thrive on our planet.
2. Revolution of the Earth
When earth spins or revolves around the sun, the movement is called revolution of the Earth.While rotating on its axis the Earth also revolves around the Sun. The path taken by the Earth while it revolution is known as the Earth’s orbit. Earth takes one full year (365 ¼ day)s to complete one revolution around the Sun.
• Change of Seasons
The revolution of the earth causes the change of seasons. It results in four seasons-summer, autumn, winter and spring. The Northern hemisphere experiences summer in June, the Southern hemisphere experiences winter at that time, and vice versa.
Leap Year
The Earth actually takes 365¼ days to go around the Sun once. But a year has 365 days. So, every four year we add a day(¼+ ¼+ ¼+ ¼ =1) to the month of February. That year is called leap year and has 366 days.
• At the North and South poles, days and nights are 6 months long: Sunrise at the South Pole is around the 21st of September every year. Sunset is around 22nd of March the following year. The reverse is the case at the North Pole. So, a polar day is about six months and the polar night is also about six months.
• On the 21st of March and 23rd of September days and nights are equal throughout the world as the sun rays are directly on the equator. These days are called Equinox.
Exercise
Ques 1. Fill in the blanks:
1. The time taken by Earth to complete one rotation is ____.
2. The motion of the earth spinning on its axis is called ____.
3. The path followed by the Earth around the Sun is called ____ .
4. An year which 366 days is called a ____ year.
5. ____ is known as the Land of Rising Sun.
6. The motion of the Earth which causes the change of seasons is called ____.
Ques 2. Correct the underlined words and rewrite the statement:
1. The Earth rotates from North to South.
2. Days and nights are formed by the rotation of the Sun.
3. The Northern hemisphere experiences summer in December.
4. The path followed by the Earth to revolve around the Sun is called the axis of the Earth.
5. Earth is the fifth planet from the Sun.
Ques 3. Answer the following questions:
1. State the difference between rotation and revolution.
2. How are days and nights formed?
3. What are the effects of rotation and revolution of the Earth?
4. The two days on which Earth experiences equal days and equal nights are? Explain this phenomenon.
5. What would havehappened if the Earth did not rotate?
6. Explain polar days and polar nights.
