Cbse class 6, Social Studies
Movements of Earth Rotation Revolution and Seasons
What is Rotation of Earth?
The spinning movement of Earth on its own Imaginary axis in the space is termed as Rotation. Not only earth all the heavenly bodies in space are rotating on its own axis.
What is Earth’s Axis?
Earth’s axis is an imaginary line that passes through north and south pole and it is tilted at an angle of 23½ degree. Earth takes 24 hours to complete one full rotation.It is called as “One Earth day”
If Earth is rotating then why don’t we feel the rotation?
Earth is rotating at the speed of 2200 km/hr.We are not feeling it because Earth is moving at the steady state and we are also moving along with it. We may experience rotation only when earth suddenly moves at faster rate.
In which direction do Earth rotates?
Everyday we see Sun,Moon and stars rising on the Eastern side and sets on western side.This means that Earth rotates from West to East.
What are the effects of rotation?
Earth takes 24 hours to complete one full rotation. This causes day and night. When one portion of the earth faces sun it is day and the other side marks the night.
Define Dawn and Dusk?
Dawn means the entire period between night and day.
Dusk means the entire period between day and night.
What is Revolution?
The movement of earth around the sun is called as revolution. The path along Earth revolves around sun is fixed and it is called as Orbit. Earth takes 365 days 6 hours to complete one revolution. Earth’s Orbit is elliptical in shape. It is called as “One Solar year”
What are the effects of revolution?
The seasons are caused by the revolution of the earth and its tilt in the Earth’s axis by 23.5 degrees. If the earth axis is not tilted, we will not experience change in the season. There are four main seasons. Summer, Autumn, Winter and Spring. Revolution causes Summer and Winter Solstice, Autumn and Spring Equinoxes.
Define Solstice?
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Solstice in latin “Sol” meaning Sun and “Sistere” meaning to stand still. Solstice occur when one of the Earth’s pole has its maximum tilt away from the sun.
Solstice occur twice the year. Summer solstice and Winter Solstice.
What are the major differences between summer and winter solstice?
| S.No Summer Solstice | Winter Solstice | |
| 1. | It is also termed as Estival solstice / Mid Summer. | It is also termed as Hibernal Solstice/ Mid Winter. |
| 2. | It is day when sun reaches its highest point in the sky. | It is the day in which when sun reaches lowest point in the sky. |
| 3. | During summer Solstice Earth’s Maximum tilt is towards the sun. | During Winter Solstice Earth’s Maximum tilt is away from the sun. |
| 4. | Summer Solstice have longer days and shorter nights | Winter Solstice have shorter daylight and longer nights |
| 5. | June 21/22 mark longer day in northern hemisphere. | December 22 marks shortest day in northern hemisphere. |
| 6. | At poles during Summer solstice there will be more brightness. | At poles during winter Solstice there will darkness or twilight. |
Note: The dates for summer and winter solstice are reversed in southern hemisphere.
What is Equinox?
Equinox comes from two lain words “aequus” means Equal and “Nox or Noctis” meaning Night.
Equinox also termed as “Equinoctial Point”
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Equinox experienced when the sun crosses the celestial equator during which day and night are of equal.
During equinox the sun is directly above the equator.
In equinox, day and night are of equal length. 12 hours day and 12 hours night. Equinox is experienced during March 20(Vernal equinox) and September 22(Autumnal equinox)
List the major differences between Vernal and Autumnal equinoxes?
| S.No | Vernal Equinox | Autumnal Equinox |
| 1. | It marks the first day of the Spring season. | It marks the first day of the Autumn season |
| 2. | It occur when sun passes the equator moving from southern to northern hemisphere. | It occurs when the sun passes the equator moving from northern to southern hemisphere. |
| 3. | North pole begins to come near the sun. | North pole begins to tilt away from sun. |
| 4. | It occurs in March 20 in northern hemisphere. | It occurs in September 22 in northern hemisphere. |
| 5. | It occurs in September 22 in southern hemisphere. | It occurs in March 20 in southern hemisphere. |
Do Equinox occur in same day every year? Explain?
No,Equinox dates varies one or two days every year. This is because earth takes 365 ¼ days to complete one revolution. The quarters are added and makes a day which we call as leap year. Leap year comes once in four years.Due to this Equinox dates varies by one or two before or after.
List the difference between Solstice and Equinox?
| S.no | Solstice | Equinox |
| 1. | Solstice occur when one of the Earth’s pole has its maximum tilt away from sun. | Equinox is experienced when sun crosses the celestial equator during which, day and night are of equal length. |
| 2. | Solstice marks longest and shortest day of the Earth. | Equinox marks the equal length of day and night. |
| 3. | There are Summer and Winter solstice | There are Vernal and Autumnal equinox |
| 4. | June 21 – Longest Day. December 22 – Shortest day. | March 20 -Vernal equinox September 22 Autumnal equinox. |
Now let us see different seasons in the world. Before knowing about seasons we need to know about the weather.
Define Weather?
Our Earth is surrounded by layer of air called as Atmosphere. Sometimes the air is hot or chill.Change in the temperature of air is called as Weather. Weather keeps on changing from day to day and from hour to hour.
Define Season?
When the weather remain same for a longer period it is referred as Seasons. Seasons are division of year, marked by change in weather,intensity of sun rays on Earth and revolution of earth around the sun. Major seasons of the world are
Summer,Autumn,Winter and Spring.
Is there is difference in seasonal change in tropical and temperate countries. Explain? Yes, there is variation in seasonal change in tropical and temperate countries.This is because the tropical countries are present in torrid zones and they receive direct rays of the sun. But in temperate countries the intensity of sunlight is comparatively less,since it receive slanting rays of sun.
| S.No | Month | Northern Hemisphere | Southern Hemisphere |
| 1. | March | Spring | Autumn |
| 2. | June | Summer | Winter |
| 3. | September | Autumn | Spring |
| 4. | December | Winter | Summer |
Spring —– March, April, May
Summer —– June,July, August
Autumn —– September, October, November
Winter —– December, January, February
Characteristics of each seasons:
| Summer | Autumn/ Fall | Winter | Spring |
| Temperature is very high | Temperature is neither hot nor cold | Temperature is very low | Temperature is neither hot nor cold |
| Hot and dry Climate | Pleasant climate | Very cold and freezing Climate | Mild and Pleasant Climate |
| Days are long Nights are short | Days and night are same length | Days are short and Nights are long | Neither short nor long days |
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| Fruits and Vegetables are in full growth. | Leaves color change and fall. | Due to snow, leaves shed all their leaves. | Trees sprout new leaves, Flowers bloom and birds build nest. |
Seasons in India:
In India there is slight change in season. We have Summer, Winter and Monsoon/Rainy
| Content | Summer | Winter | Monsoon/Rainy |
| Month | April, May | November, December January | June, July August |
| Temperature Hot and dry | Climate | Air is cool Sun is not bright | Cool winds from sea form clouds brings rain |
| Water bodies | In some places lakes and ponds dry | Lakes and pond freeze mainly in North India | Lakes and ponds are filled with rain water |
| Dress | Colorful cotton clothes | Warm Woolen Clothes | Warm clothes we use Rain coat when it is raining. |
| Crops | Fruits and Vegetables are in full growth | Trees shed leaves due to extreme Chillness | Crops looks fresh and green |
| *Seasonal Fruit | Mangoes,Plum Black and blue berries etc. | Lemons, Oranges, Grapefruit etc. | Apples,Apricot Avocado etc |
*Seasonal fruits refers to some fruits and vegetables are harvested only during particular seasons. Eating seasonal fruits keeps our body healthy and it is economical too.
What is Hibernation?
Hibernation is a period during which animals remain in dormant (inactive) stage. It is 6/7
mainly during winter. During hibernation period the animals have a low body temperature, low metabolic rate. Ex: Polar bears, Hedgehogs etc.
Define Migration?
Migration usually refers to movement of birds from one region or place of habitat to another. Mostly birds fly north in spring to breed in temperate countries and return in autumn in warmer regions to south.
Ex: Geese flying south for winter.
Thanks.
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