Desert Diary
March 28, 2002

Physics/Boiling Water

     

This page was designed with CSS, and looks best in a CSS-aware browser--which, unfortunately, yours is not. However, the document should still be readable, though not presented in the most sophisticated manner.

Living deep in our sea of air, we are no more aware of weight impinging upon us than a sea-dwelling fish under tons of water. Yet, at sea level, some 14 pounds of air press against every square inch of our bodies, equalized by internal counter pressure. Only as we move from low desert into the highlands do some facets of this pressure become evident, as when shortness of breath reminds us of thinning air.

In these modern days of sophisticated instrumentation, we tend to forget the practical difficulties of the past--of even determining something as seemingly simple as elevation. Early exploratory pushes into the Southwest by United States forces took advantage of the decreasing weight of air as one ascends to estimate, in a roundabout way, the distance above sea level. As people who cook at high elevations soon learn, water boils at lower and lower temperatures as the air pressure on its surface decreases. Simple conversion tables and a thermometer reveal a camp's elevation by merely noting the temperature at which the coffee water boils.

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.

References

Web Resources