Scaling things up in size has some funny and important results. When you enlarge something without changing its shape, its volume increases more rapidly than its surface area. Think of a cube 1 inch on a side. The six sides give 6 square inches for the surface area compared to 1 cubic inch for the volume. At double the size; each side has 4 square inches for a total area of 24 square inches, four times the original; but the volume now is 8 cubic inches, eight times the volume of the original cube.
Important? Think of the spring dust storms in the desert. The dust is lifted by friction between the wind and the particles. Luckily for us, the bigger particles have less surface area compared to their volume, and that additional volume means relatively more weight. Luckily, wind friction works on the surface area, and so the friction isn't enough to lift the larger particles off of the ground. If it weren't for the volume-surface relationships—well, care to think about 10-pound boulders hurtling through the air?
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
