Seasons: Earth’s Rotation and Revolution

Observation of Seasons

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.

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

The cycles we notice result from this rotation and revolution of the Earth. Earth’s motions are responsible for 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 the stars appear to change their position in the sky.

Explanation:

Earth’s axis is tilted 23.5 degrees from a line perpendicular to the plane of its orbit. The tilt of Earth’s rotation causes the angle at which the Sun’s rays strike Earth’s surface to vary through the year.

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.

The Earth orbits the sun in a year. It tilts on its axis and circles the sun in an elliptical pattern. Small changes in the angle of Earth’s tilt and the shape of its orbit around the Sun bring about climate change. 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.

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 21^st March and September 23^rd, 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.

Observation:

1. The equator receives vertical sun rays from the sun on March 21 and September 23.
2. Both the North and South Poles are located at an equal distance from the sun.
3. The length of days and nights is the same everywhere.
4. The earth’s hemispheres are neither extremely hot nor extremely cold. The spring season begins on March 21 and the autumn season begins on September 23 in the Northern Hemisphere. In the southern hemisphere, it is the opposite.
5. The times of sunrise at one pole and sunset at the other coincide on the equinoxes.

The Earth‘s Revolution Around the Sun:

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 the 21^st of 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.

Observation:

1. While the south pole is tilted away from the sun, the north pole is inclined toward it.
2. The tropic of Cancer (23 1/2°) is covered by the vertical fall of the sun’s rays.
3. The sun heats and illuminates a large section of the northern hemisphere.
4. In the northern hemisphere, the day lasts longer than the night. The place in the northern hemisphere experiences the summer season.
5. On June 21, the northern hemisphere experiences its longest day and its shortest night.

In the southern hemisphere, all the previous circumstances are reversed.

Winter Solstice:

The Winter Solstice occurs on 22^nd 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.

Observation:

1. The North Pole is turned away from the sun, whereas the South Pole is inclined toward it.
2. Over the tropic of Capricorn (23 1/2° S), the sun’s rays are directed vertically.
3. The sun heats and illuminates a significant section of the southern hemisphere.
4. In the southern hemisphere, the days are longer than the nights. It is summer in several parts of the southern hemisphere.
5. In the southern hemisphere, the longest day and shortest nightfall are on December 22.

In the northern hemisphere, all the above circumstances are reversed.

Situations at Arctic and Antarctic Circles:

During the summer solstice in the northern hemisphere, the Sun will never set in the Arctic Circle and never rise in the Antarctic Circle.

During the winter solstice in the northern hemisphere, the Sun will never rise in the Arctic Circle and never set in the Antarctic Circle.