Kelvin, Perry and the Age of the Earth

Fourier had shown that temperature changes within a solid obey the diffusion equation, in which the rate of change of temperature at a point is proportional to the second spatial derivative of the temperature (the curvature of the line on a temperature-distance plot), with the constant of proportion...

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Bibliographic Details
Published in:American scientist 2007, Vol.95 (4), p.342
Main Authors: England, Philip C., Molnar, Peter, Richter, Frank M.
Format: Article
Language:English
Subjects:
Age
Earth
Heat transfer
Physics
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Summary:Fourier had shown that temperature changes within a solid obey the diffusion equation, in which the rate of change of temperature at a point is proportional to the second spatial derivative of the temperature (the curvature of the line on a temperature-distance plot), with the constant of proportionality being a property of the material called thermal diffiisivity . (This simple physical principle underlies the advice given in many cookbooks that one should take the turkey out of the oven as much as an hour before carving it, because its interior will continue to cook, without the exterior's drying out.) For the sake of having concrete numbers to use in this thought experiment, assume a temperature difference of 200 degrees Celsius between the interior of the oven and the interior of the freezer; 180 degrees is a pretty good temperature for roasting turkeys, and -20 degrees is a pretty gocxl temperature for freezing ice cream.
ISSN:0003-0996
1545-2786
DOI:10.1511/2007.66.3755