Movement of the Earth |Effects of Rotation & Revolution

While standing here on the earth we might not observe its movement. But two movements of the earth take place simultaneously. These are rotation and revolution. The rotation and revolution affect the environment on earth in many ways. In this post, we will learn about the effects of rotation and the revolution of the earth.

The main effects of the rotation of the earth are:

• The occurrence of day and night,
• Change in the direction of wind and ocean currents.

The main effects of the revolution of the earth are:

• Change in seasons.

ROTATION

Have you seen a top spinning?

The movement of the earth on its axis is called Rotation. The earth also spins like a top.

The earth spins from west to east on an imaginary line or axis passing through its center. This imaginary axis passes through the Geographic North and South Poles and tilts at an angle of 66-1/2^o to the plane of the earth’s orbit.

Effects of Rotation of the Earth

Some important effects of the rotation of the earth are:

• The earth takes 24 hours to complete one rotation around its axis. To be precise earth takes 23 hours 56 minutes and 40.91 seconds to complete this movement. The rotation of the earth causes day and night. As the earth rotates on its axis, the portion of the earth facing the Sun experiences Day. The other portion which is away from the Sun experiences Night. As the earth keeps rotating, day and night occur alternately.
• The rotation of the earth affects the direction of the winds.
• It also affects the direction of the flow of water in the oceans.

Japan lies in the extreme east and sees the Sun first. Thus, it is called the land of the Rising Sun. Its time is ahead of places in the West.

REVOLUTION

The movement of the earth around the Sun in its orbit is called Revolution.While the earth rotates on its axis, it also moves around the Sun along a fixed elliptical path. This fixed path is called Orbit. Although we might not feel it, but the Earth whirls through space nearly at the speed of 30 km/s. The earth completes this journey around the sun in one solar year i.e. 365-1/4 days.

The earth takes 365-1/4 days to complete one revolution around the Sun. To be precise it is 365 days 5 hours 48 minutes and 45.51 seconds. However, our calendar shows only 365 days in a year. So, what happens to 1/4 day? So, to correct the same, after every four years, we add this 1/4 day as one extra day to February. This year is known as the leap year with February having 29 days.

Effects of Revolution of the Earth

One of the most important effects of the revolution of the earth is that it causes Seasons.

Causes of change in seasons are:

1. The revolution of the earth around the sun, and
2. A fixed inclination (tilt) of the earth’s axis at an angle of 23-1/2^o to its plane of rotation.

As the earth rotates and revolves around the Sun, one part of the earth tilts towards the Sun and the other part away from the Sun. The part of the earth that tilts towards the Sun gets more sunlight and has Summer, whereas, the other part away from the Sun receives less sunlight and has Winter. When the North Pole tilts towards the Sun, the Northern Hemisphere experiences the Summer season, and the Southern Hemisphere experiences the Winter season. Similarly, when the South Pole tilts towards the Sun, the Southern Hemisphere experiences the Summer season, and the Northern Hemisphere experiences the Winter season.

The four seasons: The revolution of the earth on its tilted axis causes seasons. The earth experiences 4 seasons in a year – summer, winter, spring, and autumn.

1. Spring: on March 21 the Sun is directly overhead the equator. This is the season of spring in the north temperate zone.
2. Summer: On June 21 the Sun is directly overhead the Tropic of Cancer. Thus, during this period the north temperate zone experiences summer.
3. Autumn: On September 23 the Sun returns to the equator, and the north temperate zone, experiences the season of autumn.
4. Winter: On December 22 the Sun is at the Tropic of Capricorn and the north temperate zone experiences winter.

In the south temperate zone, the seasons are the reverse of those mentioned above, at the same time of the year.

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OTHER EFFECTS OF ROTATION AND REVOLUTION OF THE EARTH

Equinox and Solstice are the two other effects of the movement of the earth.

Equinox:

‘Equi’ means equal and ‘nox’ means night, so Equinox means equal day and night. There are two days in a year when the sun shines directly over the equator, and day and night are equal.Equinoxes are those dates when the nights and days are equal. During the movement when both the poles of the earth are at an equal distance from the Sun, the rays of the Sun fall directly on the equator. Therefore, on this day the Earth experiences an equinox. An equinox occurs twice a year, one on March 21 and another on September 23. On March 21, the earth experiences Spring or Vernal equinox. On September 23, it is the Autumnal Equinox.

Solstice:

‘Sol’ means Sun and Solstice means standing still of the Sun. There are two days in a year when the Sun shines brightly on the Tropic of Cancer and Tropic of Capricorn.The solstice is the time of the year when the difference between the length of days and the length of nights is the largest. During these days the sun shines vertically over a tropic. On June 21 the Sun shines directly on the Tropic of Cancer. All the places in the Northern Hemisphere experience their longest day on this date. This is called Summer Solstice. When the South Pole tilts towards the Sun, the Southern Hemisphere experiences the summer season, and the Northern Hemisphere experiences the winter season. The Sun shines brightly on the Tropic of Capricorn. On December 22, Northern Hemisphere experiences the shortest day. This is Winter Solstice. The reverse is true in the case of the southern region.

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