The sun's light and warmth fall unequally on the northern and southern halves of the planet, so during different seasons, the Northern Hemisphere is tilted toward or away from the sun, meaning the temperatures and daylight wax and wane.

During an equinox, places around the globe experience nearly equal amounts of daytime and nighttime. The second occurrence this year happens on Sunday.

The autumnal equinox brings fall to the Northern Hemisphere today as the sun passes directly over the equator at noon. But are day and night actually equal length today?

The autumn equinox, which comes around every September for the Northern Hemisphere, marks the official astronomical start of fall. This year, the equinox arrives Sunday, Sept. 22 at 8:44 a.m. Eastern, according to The Farmers' Almanac.

If you get up early enough, you can experience an equinox sunrise. The autumnal equinox heralds the arrival of fall in the northern hemisphere.

Today marks the autumnal equinox, or the first day of astronomical fall. Have you ever wondered why it occurs on a different day and at a different time each year? Let’s break it down! Let’s start with the basics.