Equinox: what it is and when the phenomenon occurs

You may have already noticed that in summer the days are longer, while in winter the nights are longer. However, there are two days of the year when day and night are (almost) equal all over the planet: the equinox.

In this matter, the he will explain to you what the phenomenon is, why it occurs and when it occurs.

What is the equinox?

The equinox is an astronomical phenomenon that occurs when the Sun is directly above the Equator. Therefore, the hemispheres receive the same amount of light and, therefore, day and night have the same length everywhere on Earth. It is from this peculiarity that the word equinox derives, which in Latin means “equal night”.

Although it occurs every year, we can say that it is a rare event. This is because the Earth obeys both a translational motion around the Sun and a motion on its axis of rotation. Consequently, the incidence of light on the hemispheres will be different on almost every day of the year, except for these two dates.

It is interesting to note that during the equinoxes the Sun rises exactly in the east and sets exactly in the west.

When does the phenomenon occur?

This event takes place twice a year: once in early fall and once in early spring. Just like the solstice, which marks the beginning of summer and winter, the seasons reverse. That is, when the beginning of autumn is celebrated in the northern hemisphere, it is the beginning of spring in the southern hemisphere, and vice versa.

Specific dates may vary slightly from year to year, due to differences in Earth’s orbit around the Sun, which takes 365 and some hours. Therefore, every four years the phenomenon is slightly delayed. Thus, the autumnal equinox in Brazil falls between March 20 and 21, and the spring equinox between September 22 and 23 – in the countries of the northern hemisphere it is the other way around.

In the 2023 calendar, it looks like this:

With information from Toda Matter (1 AND two).

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Source: Olhar Digital