The equinox is the moment when the circle of illumination passes through the poles as a result of the Sun's rays hitting perpendicular to the Equator.

During the Spring Equinox on March 21, which heralds spring, day and night are actually equalized. This happens twice a year, in spring and fall.

In the Northern and Southern Hemispheres, the Sun's rays fall at an angle of 90° to the Equator at noon. At that moment the shadow length is zero at the equator. From this date, the Sun's rays begin to fall perpendicular to the Northern Hemisphere. From this date, the days begin to be longer than the nights in the Northern Hemisphere. In the Southern Hemisphere, the opposite happens. This date is the beginning of Spring in the Northern Hemisphere and the beginning of autumn in the Southern Hemisphere. The circle of illumination is tangent to the poles, and the Sun is visible at both poles on this date. On Earth, the duration of day and night is equal to each other. This date is the beginning of six months of night time at the South Pole and the beginning of six months of day time at the North Pole.

Every year there are two equinoxes on Earth: one on March 21, called the vernal equinox, and the other on September 22, called the autumnal equinox, with different dates in the Northern and Southern Hemispheres.

The March equinox is the vernal equinox in the Northern Hemisphere and the autumnal equinox in the Southern Hemisphere. Likewise, the September equinox is the fall equinox in the Northern Hemisphere and the spring equinox in the Southern Hemisphere.


There are many more effects that we can all notice at the time of the March equinox. In the Northern Hemisphere, the March equinox allows the sun to rise earlier, set later and plants to sprout.

South of the equator, it is the opposite season - later sunrise, earlier sunset, colder winds, drying and falling leaves.

Equinoxes and solstices are caused by the tilt of the Earth on its axis and the relentless motion of its orbit. You can think of the equinox as an event in the imaginary dome of our sky, or as an event in the Earth's orbit around the Sun.


March 21 (equinox): Day and night become equal, spring begins in the northern hemisphere, while the southern hemisphere enters autumn.

June 21 (summer solstice): The longest day and shortest night of the year.

It is also known as the summer solstice. Summer begins in the northern hemisphere while winter begins in the southern hemisphere.

September 23 (equinox): Day and night become equal. In the northern hemisphere, summer ends and fall begins. In the southern hemisphere, it is the transition to spring.


1- The Sun's rays come perpendicular to the Equator.

2- The Sun's rays come at the same angles to both hemispheres.

3- Tidal amplitude increases in stagnant waters on Earth.

4- From March 21 to September 23, the days are longer in the Northern Hemisphere than in the Southern Hemisphere as the rays are perpendicular to the points north of the Equator. From September 23 to March 21, the days are longer in the Southern Hemisphere than in the Northern Hemisphere.

5- March 21 is the start of 6 months of daylight at the North Pole and September 23 is the start of 6 months of daylight at the South Pole. At the equinoxes, the Sun rises exactly in the east and sets exactly in the west.

6- Although the amount of energy coming from the Sun to both hemispheres is equal, the temperatures are not equal due to different temperature accumulation.

7- Since the Sun's rays pass tangentially to the poles, the circle of illumination is formed over the poles. Twilight is experienced at the poles.

8- Day and night periods are equal all over the world (Equinox).

9- The Sun rises and sets at the same time at all points on the same meridian.

10- It is the beginning of the spring seasons in both hemispheres. March 21 is the spring of the Northern Hemisphere and the fall of the Southern Hemisphere. September 23 is the spring of the Southern Hemisphere and the fall of the Northern Hemisphere.

How About a Vacation in the Solar System?

How About a Vacation in the Solar System?

Hey there, future space explorers! Get ready for an out-of-this-world journey through our solar system, where planets come alive with amazing facts and cool comparisons.

Why Do Astronauts Wear Space Suits?

Why Do Astronauts Wear Space Suits?

Why do astronauts wear space suits? Is the space environment dangerous for humans? In this article, we examined astronaut suits.



NASA aims to launch manned missions to the Moon again. Although one of the main goals here may seem to establish a permanent settlement on the lunar surface, the real goal is actually much bigger.

Pi Day

Pi Day

In many parts of the world, March 14th, the 14th day of the 3rd month, is celebrated as "Pi Day" every year.

Go To Top