Solstices & Equinoxes, Meaning, Difference, Diagram

Solstices and Equinoxes Meaning

A solstice and equinox are diametrically opposed. The earth’s seasons are caused by equinoxes and solstices. Seasons change on Earth because the planet is slightly tilted on its axis as it orbits the Sun. This means that at different times of the year, different parts of the Earth receive more or less sunlight. If the Earth were not tilted, the Sun would always appear directly above the Equator, the amount of light received at any given location would be constant, and there would be no seasons. There would also be no need to mark the equinoxes or solstices.

Solstices and Equinoxes Dates

On 21^st June, the Sun is vertical over the Tropic of Cancer. For every place, above the Tropic of Cancer, the sun is at the highest point in the sky. The northern hemisphere has the longest day on this day. At the Arctic Circle, the sun never sets below the horizon. This event is called the Summer Solstice.

On 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole is tilted toward the sun. The sun’s rays fall vertically at the Tropic of Capricorn. The sun doesn’t set below the horizon at the Antarctic Circle.  This event is called the Winter Solstice.

The equator receives direct sunlight on March 21st and September 23rd. Neither the North Pole nor the South Pole is tilted towards the Sun, as a result of which, all the places on earth experience equal days and equal nights. This event is called equinox- meaning equal night.  23rd of September is the Autumn Equinox while the 21st of March is Spring Equinox.

Solstices and Equinoxes Diagram

Below are the diagrams of  Solstices and Equinoxes:

Equinox Meaning

The Equinox is the time of year when the day and night are equal. This event occurs twice a year. The Dates of Equinox are on March 20 and September 23. An equinox occurs when the plane of the earth’s equator passes directly through the geometric plane of the sun, implying that the centre of the visible portion of the sun falls directly over the equator.

Vernal Equinox & Autumn Equinox

The vernal equinox occurs in the Northern Hemisphere in March, while the autumnal equinox occurs in September. In the case of the southern hemisphere, the opposite is true. The equinox date can change due to a variety of factors, including the leap year.

Without regard for the hemispheres, the generic names for both equinoxes are Northward equinox and Southward equinox. A Northward equinox, as the name implies, occurs when the Celestial equator is crossed by the solar declination in the northward direction and vice versa.

In most parts of the world, the northward equinox marks the start of spring and is celebrated as the new year on the Hindu, Persian, and Iranian calendars. The autumn season begins with the southward equinox. The equinoxes are the times of the year when the sun shines equally in both hemispheres of the earth.

This is also why, during an equinox, the sun appears to rise at one rotational pole of the Earth and set at the opposite rotational pole for an observer. This implies that the equinox is the time of year when the sun’s rays fall directly on the equatorial plane.

One notable effect of an equinox is that on days surrounding an equinox, the sun is directly behind the earth, causing the high energy to disable and overload geostationary satellite reception circuits. These effects can last anywhere between a few minutes and an hour.

Solstices Meaning

It is a Latin word that means ‘stalled sun’. It is a natural phenomenon that occurs twice a year in each hemisphere of the earth, once in the summer and once in the winter.

A solstice is an event that occurs when the sun appears to reach its most northerly or southerly expedition relative to the celestial equinoctial line on the celestial sphere. The term solstice comes from the Latin language. A year has two solstices.

Summer Solstice: The solstice occurs on either of the hemispheres that receives the most sunlight during the year.

Winter Solstice: Except for the equator, the day of the solstice has the least amount of sunlight of the year.

Summer Solstice & Winter Solstice

The Summer Solstice Date is on June 21st, and the Winter Solstice Date is on December 21st. Seasons are defined in several countries by references to the solstices and equinoxes. The latitude of the Earth interacts with the solstice in a variety of ways. The solstice is a maximum of radical exposure to sunlight at the poles, while it is barely noticeable at the Equator.

The solstices are referred to as the ‘June Solstice’ or the ‘December Solstice.’ The sun reaches its highest point in the sky for any observer on the North Pole in June; this is known as the June solstice. Similarly, the sun reaches its highest position in the sky for any observer on the south pole in December; this day is known as the December solstice. At the solstice, the sun is said to be standing. Throughout history, the winter solstice has been a significant time of year in many cultures. It also depicts the sun’s symbolic demise and rebirth.

Sun declination is approximately 23.5°N during the June solstice and 23.5°S during the December solstice. Because of the Earth’s axial tilt of 23.5°, the sun’s rays are extremely intense in either the Southern or Northern Hemispheres. The summer solstice is the longest day of the year, while the winter solstice is the shortest.

Solstice Geography Behind

The tilt of the Earth is responsible for the changing lengths of the days. The axis of rotation of the Earth is tilted at an angle of 23.5° to its orbital plane. This tilt, combined with factors such as the Earth’s spin and orbit, causes variations in the duration of sunlight, resulting in different lengths of days in different parts of the planet. The Northern Hemisphere is tilted in the direction of the Sun for half of the year, receiving direct sunlight during long summer days. It tilts away from the Sun during the other half of the year, making the days shorter. The tilt is also responsible for the Earth’s seasons.

This phenomenon causes the Sun to move from the northern to the southern hemispheres and vice versa, resulting in seasonal changes throughout the year.

Difference Between Solstices and Equinoxes

The below table shows you the difference between Solstices and Equinoxes:

Solstices and Equinoxes UPSC

The equinox and solstice are astronomical landmarks. During the equinox, the earth is either directly beneath or directly above the sun. The solstice occurs when the sun is at its highest point away from the Earth. Solstice is a significant event for farmers because it marks the beginning of the growing season.

This topic holds immense importance for the UPSC CSE examination and every aspirant should be well-prepared in this particular area.

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