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Re: [Phys-l] Bad physics in National park



Maybe I missed the point, but it really doesn't matter if the air is exposed to the sun or not. Air is basically transparent to sunlight so its temperature is really set by its interaction with the ground (conduction - convection). The temperature in the shade is usually a pretty good indicator of air temperature. In fact, reporting stations have thermometers placed in louvered boxes to prevent direct sunlight from striking the thermometer while providing a relatively free flow of air. The sunlight striking your body, of course, makes it feel hotter.

Bob at PC

________________________________________
From: phys-l-bounces@carnot.physics.buffalo.edu [phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Jacques Rutschmann [jr@colororange.com]
Sent: Saturday, May 23, 2009 12:57 PM
To: phys-l@carnot.physics.buffalo.edu; 11AA Jacques
Subject: Re: [Phys-l] Bad physics in National park

Grand Canyon National Park rangers are concerned about heat exhaustion:
At the bottom of the Grand Canyon, near Phantom Ranch, there is (was?) a
thermometer on a post with a sign that warns that the temperature is
whatever is indicated, but "yet higher in the sun". It seems that the
rangers are not aware that the temperature is a measurement of the
surrounding air. That air might or might not be in the sun, depending on
time of day and cloud cover. Maybe that's nitpicking, but National Parks
claim to educate the public on science, ecology, history etc...
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