The discussion about the meaning of "Kraft" illustrates the
difficulties we can have with communication of scientific ideas because
of the meanings of words. The example I use with students is that in
everyday language we use the words "force", "energy", and "power"
interchangeably, yet each of these things has a very precise unique
meaning in physics. However, even physicists are not always as careful
as they should be. Some time ago I grumbled on this list about how
we ourselves use the word "velocity" when we should use "speed". And
it's fascinating to look at how words were used in the past. Several
examples can be found in Joule's paper describing his paddle wheel
method for measuring the mechanical equivalent of heat, which is
reprinted in "Great Experiments in Physics", edited by Morris Shamos
(from Dover Press). Joule constantly uses "temperature" to mean "heat"
and "force" to mean "energy". His conclusion is that "773.64
foot-pounds will be the force which ... is equivalent to 1 [degree]
Fahr. in a lb of water". It reminds me of the statement by a Fermilab
physicist in the first "Infinite Voyage" program on PBS many years
ago, in which he informed us that 'the total energy collected by all
the radio telescopes that have operated is less than the force of a
single snowflake landing on the ground'.