Fall has arrived! The days are getting shorter and the breeze is becoming crisp. Cheeks are flushed and we are undeniably drawn to step on that particularly crunchy looking leaf.

Autumn is more than just a demarcation of time and a change in wardrobe-it is an astronomical event. All of our seasons result from the tilt of the Earth's axis in combination with the Earth's elliptical orbit around the sun.

"Right now we are in the Autumnal equinox, from our perspective it looks like the sun is getting lower in the sky because the northern hemisphere is tilting away from the sun," said BYU astronomy professor J. Ward Moody.

When the Northern hemisphere is tilted away from the sun and we are near the perihelion, which is the part of the ellipse farthest away from the sun, our days become shorter, triggering an adjustment of color.

According to the United States Forest Service, leaves change color because the amount of sunlight that reaches them is reduced.

The reduced amount of sunlight slows the production of chlorophyll and the veins in the leaf that carry nutrition to the tree are sealed up in preparation for winter.

As the chlorophyll breaks down the production of carotenoids and anthocyanins begin. Carotenoids and anthocyanins are molecules that give fruit vivid color and show bruising. Without the overpowering green-colored chlorophyll the leaf shows its true colors.

Many students enjoy the change.

"I like the different colors of the trees, and I don't mind the cold," Kristen Gardener, a freshman from Idaho, said.

Fall holds benefits other than aesthetic pleasure.

"This is just a beautiful place, and in the fall my lips don't get too chapped," Jeff Murphy, a political science major from Calif., said.

While commenting about the cooler weather, Marshall Coe, a pre-law major from Cheyenne, Wyo., said, "This is a nice summer day in Wyoming. I actually really like it."

In the end, most students like autumn for the change, the flash of color and of course the gratifying crunch, as expressed by exercise science major Angelita Hendricks: "I like to step on crunchy leaves, the crunch is ... satisfying."



Copyright Brigham Young University 27 Oct 2008