See how our seasons come from Earth's tilt and yearly loop around the sun, which changes the ice cover, vegetation, and sunlight across the planet.

The official first day of fall, otherwise known as the autumnal equinox, is this weekend in the Northern Hemisphere. According to Encyclopedia Britannica, it is one of only two days, the other being the vernal equinox, when the sun is directly above the Equator, essentially dividing night and day into equal portions.