Autumnal Equinox: What You Should Know About It

The autumn equinox, which arrived at 10:21 a.m. ET on September 22, marks the advent of fall in the Northern Hemisphere and autumn in the southern. The term equinox is derived from the Latin word for equal nights, which refers to the nearly perfect split of 24 hours into 12 hours of day and night respectively, which takes place only on the two equinox days in a year.

The equinox is linked to the very reason due to which our planet has seasons. The Earth's axis has a23.5 degree tilt in relation to its orbital plane, which implies that as our planet orbits the sun, different hemispheres inch closer or farther away from sunlight. An equinox is a geometrical alignment of our star and planet, in which the former is positioned right above the latter's equator. Therefore, during an equinox, both the Northern and Southern Hemispheres receive nearly the same amount of sunshine. Furthermore, the spring and autumn equinoxes see the sun rising due east and setting due west.

Incidentally, the Northern Hemisphere will tilt farther away from the sun, which implies it will get sunlight at a steeper angle, as we proceed towards December. The occurrence will also result in longer shadows and cooler conditions which herald the advent of winter. Gradually, the sun will be seen reaching its lowest point, which will mark the December solstice. Incidentally, the changing of seasons has been, and continues to be, celebrated historically all around our world.  

The phenomena of equinoxes and seasons occur on other planets too, however on more extreme levels. For instance, the tilt of Mars is similar to our planet, resulting in a season pattern similar to ours; however, its distance from the sun means that winter lasts for 154 days on the red planet. On the other hand, Uranus with its 90-degree tilt and 84-year orbit has a 42-year long winter.