Alva Review-Courier -

NEW YORK (AP) — Fall is in the air — officially.

The equinox arrives on Saturday, marking the start of the fall season for the Northern Hemisphere.

But what does that actually mean? Here's what to know about how we split up the year using the Earth's orbit.

WHAT IS THE EQUINOX?

As the Earth travels around the sun, it does so at an angle.

For most of the year, the Earth's axis is tilted either toward or away from the sun. That means the sun's warmth and light fall unequally on the northern and southern halves of the planet.

During the equinox, the Earth's axis and its orbit line up so th...