My recent re-reading of parts of Principia reminded me of a quote I
mostly remember, but for which I have lost the exact wording and author.
I am hoping someone on the list can help me re-attribute it. First some
background: When Newton stated his 3rd law, he used the example of a
horse pulling on a stone to explain the law.
"LAW III. To every action there is always opposed an equal reaction; or
the mutual actions of two bodies upon each other are always equal, and
directed to contrary parts."
"Whatever draws or presses another is as much drawn or pressed by that
other. If you press a stone with your finger, the finger is also pressed
by the stone. If a horse draws a stone tied to a rope, the horse (if I
may so say) will be equally drawn back towards the stone: for the
distended rope, by the same endeavour to relax or unbend itself, will
draw the horse as much towards the stone as it does the stone towards
the horse, and will obstruct the progress of the one as much as it
advances that of the other."
Later, someone was interpreting Newton's 3rd law to mean there is no
difference between action and reaction, and that cause and effect are
indistinguishable. At this point, someone else responded with the quote
I am trying to pin down, which I paraphrase here: "I am certain Newton
did not expect us to believe that stones skulk willfully about the
English countryside, sneaking up on unsuspecting horses and dragging
them hither and yon."
Is anyone familiar with the exact quote, and its author?
\\//,
Larry
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Larry Cartwright <exit60@ia4u.net>
Physics and Physical Science Teacher
Charlotte HS, Charlotte MI USA
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