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# Earth’s Revolution, Rotation, and Tilt

Class 7
Jun 12, 2023

Introduction:

An imaginary line that passes through the North and South Poles is known as the Earth’s axis. The Earth rotates by spinning over its axis.

The Earth moves around the Sun as it rotates around its own axis. It is known as the Earth’s revolution.

The cycles we notice result from this rotation and revolution of the Earth. The Earth’s motions are responsible for the change in day and night, the seasons, and the tides.

The Earth’s one full rotation on its axis lasts for 24 hours. The duration of that rotation is called one day. During this rotation, the side of the Earth facing the Sun is always in the light (daytime). It is dark (nighttime) on the side that faces away from the Sun.

The planet Earth rotates counterclockwise when viewed from the North Pole. As Earth turns, the Sun, the Moon, and stars appear to change their position in the sky.

Explanation:

You may observe the Sun traveling from east to west across the sky as the Earth spins. In the east, the sun rises, and in the west, it sets.

It appears that way because of the Earth’s rotation.  As Earth rotates counterclockwise. The Sun, the Moon, and the stars appear to change position in the sky.

## Earth’s Spin, Tilt, and Orbit

The amount of solar radiation received by any region of the Earth depends on various factors such as

• Earth’s spin
• Earth’s tilt
• The changes in the shape of the Earth’s orbit

Small changes in the angle of Earth’s tilt and the shape of its orbit around the Sun bring about changes in climate.

### Earth’s Rotation: Proof

In order to demonstrate the rotation of the Earth in 1851, French scientist Leon Foucault created Foucault’s pendulum. That was the first time it had been demonstrated experimentally.

### Foucault’s Experiment

He hung a heavy iron weight from a long wire. He pulled the weight to one side and then released it. The weight swung back and forth in a straight line.

Observation:

If Earth did not rotate, the pendulum would not change direction as it was swinging. But it did, or at least it appeared to. The direction of the pendulum appeared to change because Earth rotated beneath it. The figure below shows how this might look.

Conclusion:

If we imagine a pendulum at the North Pole. The pendulum always swings in the same direction. But because of Earth’s rotation, its direction appears to change to observers on Earth.

The freely swinging Foucault’s pendulum exhibits a predictable shift in route, supporting the rotation of the Earth.

### Earth’s Revolution, Rotation, and Tilt:

The Earth orbits the Sun in a year. It tilts on its axis and circles the Sun in an elliptical pattern. All these variables have an impact on how much solar energy we receive, which in turn affects the climate of the Earth. Seasonal variations result from the tilt of the Earth, whereas daily variations in light and temperature are caused by its rotation.

#### Seasonal Changes and Earth Rotation:

The orbital axis and the Earth’s rotation axis are tilted at an angle of around 23.5°. Due to this inclination, seasons such as spring, summer, autumn, and winter fluctuate.

From June to August, the sun shines more brightly in the northern hemisphere. As a result, winter arrives in the southern hemisphere while summer arrives in the northern hemisphere.

#### The Earth Tilts on Its Axis

The Earth is tilted on its axis. This means that as the Earth rotates, one hemisphere has longer days with shorter nights. At the same time, the other hemisphere has shorter days and longer nights.

For example, in the Northern Hemisphere summer begins on June 21. On this date, the North Pole is pointed directly toward the Sun. This is the longest day and shortest night of the year in the Northern Hemisphere. The South Pole has pointed away from the Sun. This means that the Southern Hemisphere experiences its longest night and shortest day.

The hemisphere that is tilted away from the Sun is cooler because it receives fewer direct rays. As Earth orbits the Sun, the Northern Hemisphere goes from winter to spring, then summer and fall.

The Southern Hemisphere does the opposite from summer to fall to winter to spring. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa.

#### The Earth‘s Revolution Around the Sun:

Every year on 21st March and September 23rd, direct rays of the Sun fall on the equator. On these days the poles of the Earth are not tilted towards the Sun; hence, the whole Earth experiences equal days and nights. These are called equinoxes.

The Summer and Winter solstice occurs when Earth’s axis is either closest or farthest from the Sun.

##### Summer Solstice:

The summer solstice occurs on 21st June when the North Pole is tilted closest to the Sun. The summer solstice brings the longest day in the Northern Hemisphere, as it is tilted towards the Sun, whereas the southern hemisphere has the longest night as it is tilted away from the Sun.

##### Winter Solstice:

The Winter Solstice occurs on 22nd December when the North Pole is tilted farthest from the Sun. The Winter solstice brings the longest night in the Northern Hemisphere, as it is tilted away from the Sun, whereas the southern hemisphere has the longest day as it is tilted towards the Sun.

### Changes in the Earth’s orbit:

The gravitational pull of the Sun, Moon, and giant planets in the solar system, primarily Jupiter and Saturn, is what propels the Earth around the Sun. The Earth’s spin, tilt, and orbit are gradually altered over a long period of time by the gravitational pull of other solar system objects.

The blue and yellow dotted ovals in the figure below illustrate how gravitational forces will gradually transform the Earth’s orbit from a circular to an elliptical shape over a period of 100,000–400,000 years. Over a period of 19,000 to 24,000 years, the tilt of the Earth changes direction.

Furthermore, the tilt of the Earth’s axis toward or away from the Sun will shift every 41,000 years. The amount of sunlight absorbed and emitted by various portions of the Earth can fluctuate when little variations in the Earth’s spin, tilt, and orbit occur over such a long period of time.

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