In class on April 8, 1997, Amber Foley asked this question: "How does the atmosphere around the earth play a role in our idea of a wilderness? Is it more wild because because it has had less human impact?" This question leads to the following thoughts: even the atmosphere has been influenced by human activities. Here's how.
The atmosphere is really a lot closer to the earth than we might think -- it is a kind of thin skin on the surface of the earth. Viewing the earth from outer space the Apollo astronauts saw the colorful earth surrounded by blackness -- effectively the atmosphere ends where the blackness (of space) begins. As David Brower remarked, "This is the sudden insight from Apollo. There it is. That's all there is. We see through the eyes of the astronauts how fragile our life is, how thin is the epithelium of the atmosphere." (McPhee, Encounters with the Archdruid, 80)
The atmosphere IS thin and we have influenced its entire structure. Not only do we penetrate the atmosphere with our rockets and satellites, but also our chemicals.
When chlorofluorocarbons (CFCs) were invented in the early 1900s, they were seen as a way in which chemistry truly improved our lives. Until then refridgeration was accomplished using natural ice or explosive, toxic gasses in refridgeration units. CFCs proved themselves to be safe, non-explosive, and cheap. We have air-conditioning now because of CFCs. In the past we have also used CFCs in spray cans and in making styrofoam containers. To visualize a key property of CFCs, think about a Teflon pan -- nothing sticks to it. In the same way, a CFC molecule is like a gaseous Teflon molecule. Nothing sticks to it. When it leaves a spray can, it doesn't react with anything. This means that it is inert.
It was just happy by itself, and that was its downfall.
It was inert to the point of passing upwards, unimpeded, all the way to the stratosphere, where it was attacked by intense ultraviolet (UV) light. The UV light broke apart the CFC molecule into reactive pieces that systematically chewed up the ozone in the stratosphere.
The ozone is important! It functions as the earth's sun screen. When you put sun screen on your hand, for example, the molecules in the sun screen absorb ultraviolet light and convert its energy to heat. The heat is much less harmful to your skin than the UV light is. (Stay tuned for more on how this harm takes place. Some nice, bright spring day toward the end of the quarter, you'll hear all the bad news about UV rays and your body!)
By the same token, the ozone layer functions as the sun screen for the earth. When UV rays hit it, an ozone molecule absorbs the light and converts it to heat. With the ozone layer healthy we are, in effect, protected by a natural sun screen with a Sun Protection Factor (SPF) 30. As we deplete the ozone layer, we decrease the SPF towards 4.
CFCs are totally human-made chemicals. They did not exist in the natural world until they were made in a laboratory by chemists. They can thus serve as a marker of twentieth century life. An interesting example of their use as markers occurred recently in Maryland when the graves of the founding family were excavated.
The central focus of the study was to study how people lived and died in the seventeenth century. Additionally researchers wanted to find out what the air was like back then. Each coffin actually consisted of several nested coffins, each sealed securely before being inserted in the next outer layer. Scientists drilled sampling holes into the outer coffins, testing the air at each level. If they found CFCs in an inner sample, they knew that the air in the sample was modern. (CFCs were ubiquitous -- open a drawer in your apartment, or check the glove compartment in your car. Sample the air anywhere and you would have found CFCs present.)
As the researchers drilled into the first coffin layer, they found CFCs. But eventually they penetrated an inner coffin without CFCs.
Today thanks to the Montreal Protocol we are beginning to diminish the CFCs in our atmosphere -- hopefully before they send many of us to our own coffins before our time!
Jeanne Small (EWU Chemistry) with Bill Youngs (EWU History)