All the
planets in our solar system have two types of motions i.e. rotation and
revolution.
The earth
also has two motions one is called rotation on its axis and revolution around
the sun.
Let’s check
out what rotation, revolution and axis are.
To understand
these movements one must know their meaning. Let’s know
about axis
What is Axis ?
Axis is an
imaginary line joining the two poles (north and south) on which the earth makes
its movement.
Rotation:
the movement of the earth on its axis like top.
The earth takes about 24 hours
to complete one rotation on its axis.
Revolution:
The movement of the earth around the sun is called revolution of the earth. The
earth takes 365 days 6 hours to complete its one revolution. While
rotating on its axis, the earth also makes a movement around the sun.
Let’s get
into detail of the movement of the earth.
Axis: It’s
an imaginary line which joins North Pole to the South Pole passing through the center of the earth. The movement of the earth is very fast. It moves at the
speed of 1600 km per hour. The axis of
the earth is tilted at an angle of 23.5 from a perpendicular to the orbital
plane. Thus the axis of the earth makes an angle of 66.5 with the plane of
earth’s orbit. This tilting of the axis is called the inclination of the
Earth’s Axis. While
rotating on its axis the earth also moves around the sun. The speed of the
earth in its journey around the sun is nearly 120,000 kilometers per hour.
Axis and
its revolution around the sun are responsible for many events like day and night,
change of seasons, etc.
Rotation
Rotation is
the moving around of the earth on its axis from west to east.
Effects of Earth’s Rotation
1.
East-west movement: You must have seen that the sun rises in the east and sets
in the west. During the day the sun appears to be moving from east to west. Because
of the earth’s movement, this phenomenon occurs. The earth moves from west east
on its axis. That’s why we see the sun rising in the east and setting in the
west.
2. Day and
night: Rotation makes day and night on the earth which affects light, heat,
humidity and wind movement.
Circulation
of air and water: The earth’s rotation causes a consistent change in the
direction of the flow of winds and ocean waters.
Read this please: Causes of Earthquake
The effect of the tilted axis
The earth
receives light from the sun. due to the spherical shape of the earth, only half
of it gets light from the sun at a time the portion facing the sun experiences
day while the other half away from the sun experiences night. The circle that
divides the day from night on the globe is called the circle of illumination. During
summer days are longer than the nights while in winter nights are longer than
days.
This
happens because of the tilted axis. The earth is tilted at an angle of 66.5
thus , the Northern hemisphere remains inclined towards the sun for about six
months. As the earth goes on its
revolution, The Northern Hemisphere is away from the sun for another six
months
Days and
night are equal on equator throughout the year as the sun rays falls directly on
it. Thus, the regions those come under
equator experience equal days and nights.
Revolution
The
movement of the earth around the sun is called revolution.
It completes one
revolution in 365 days 6 hours. For our convenience we count only 365 days in a
year and ignore 6 hours. The six hours becomes one day after every fourth year
and that’s why we add one more day in the month of February (called leap year)
which usually consists of 29 days.
 |
| Revolution around the sun |
Let’s find
the out other effects of revolution of the earth.
Changing Seasons
While
rotating on its axis the earth also makes a movement around the sun called
revolution. Thus changing seasons are due to both rotation and revolution of
the earth.
The
particular portion of the earth keeps facing sun light for about six months
during the course of its revolution.
Thus the
area around the earth receives maximum heat is summer. As it moves towards Polar
Regions the sun rays decreases causing changes in the season on the earth.
Let’s
understand through the dates here
Rotation
and revolution takes place simultaneously causing the seasonal changes on the
earth
21 June
North Pole
is inclined towards the sun. The sun rays directly fall on tropic of cancer.
Thus, all the regions that come under the tropic of cancer have summer causing
longer days and shorter nights in Northern Hemisphere. It is also called summer
solstice.
22 December
This is
just reverse position of 21 June. North Pole is away from the sun while South
Pole inclined towards the sun. Sun rays vertically fall on tropic of Capricorn.
Days are longer and nights are shorter in Southern Hemisphere. Thus, summer in
southern hemisphere as in Australia, South America and winter in the northern
hemisphere as in England, India. It is known as Winter solstice.
21 March
Neither
North nor South Pole inclines towards the sun. Thus sun rays fall directly on
the equator. Sun rays passes through
both the poles.
As result
all places on earth have equal days and equal nights. This is called equinox
(Vernal or spring equinox)
23 September
It is
autumn in the Northern Hemisphere and is called the Autumn Equinox.
In the
Southern Hemisphere, the seasons are opposite to the seasons in the Northern
Hemisphere. It is also called Autumn Equinox.
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