From: Paul Doherty (pauld@exploratorium.edu)
Date: Wed Sep 15 1999 - 12:24:26 PDT
Message-Id: <l0311070db405a0a2c304@[192.174.2.173]> Date: Wed, 15 Sep 1999 11:24:26 -0800 From: Paul Doherty <pauld@exploratorium.edu> Subject: ABC report on physcical sci text errors
Last week ABC news did an expose on Physical Science textbooks.
They reported (gasp!) that there were errors in the textbooks.
We all know that. Unfortunately the "error" they chose to use to illustrate
that there were mistakes was this one.
"People weight less on mountains than in mines."
The unfortunate part of this is that it is not an error.
The reviewer must have assumed an earth of constant density.
In a constant density earth a person's weight decreases with depth. So that
it is theoretically possible that a person would weight less in a mine than
on a mountain. But in the real earth which is denser at the center the
force of gravity actually increases with depth at least down to the depth
of the deepest mines.
Also if the reviewer were to actually do the numbers he (it was a he) would
find that the decrease in weight (assuming again the constant density
earth) in the deepest mine (about 3 km down) is the same as the reduction
in weight on a 1500 meter high mountain. A rather short mountain.
The moral is when you're picking an easy target for errors like a physical
science book at least make sure that you pick a real error.
Paul D
Paul "But it is more complicated than that!" Doherty,
Senior Staff Scientist, The Exploratorium.
pauld@exploratorium.edu, www.exo.net/~pauld
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