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.

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?

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