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Desert Diary
Physics/Phlogiston Theory


People are often surprised that scientists usually consider that theories cannot be proven, only potentially disproven. Instead, scientists talk of having great confidence in explanations such as the atomic, heliocentric, and evolution theories, but having less confidence in theories with weaker evidence. Why this great caution by scientists? Perhaps because they've seen strong theories overturned in the past.

Consider the phlogiston theory of the late 17th and much of the 18th century. This held that burnable substances consisted of the true substance, called the calx, and phlogiston. Burning was the escape of phlogiston, and the calx was the dephlogisticated material. Air, though, could hold only so much phlogiston, so burning in an enclosed space saturated the air, and with the phlogiston no longer able to escape, the flame went out. A lit candle in an overturned glass tumbler shows this nicely.

Phlogiston theory explained the burning phenomenon beautifully for a long time, but was doomed when the present-day theory of combustion explained more and explained it better. Good theories explain phenomena very well; better theories explain them even better.
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Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


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.