Date: Tue, 25 May 1999 10:16:00 +0000
From: HEIDI STRAHM BLACK <blackh@ognet.esuhsd.net>
To: Pinhole Listserv <pinhole@exploratorium.edu>
Subject: math & science
Sarah,
Inverse square is a natural consequence of spreading out in straight
lines. If you haven't already seen Paul Hewitt's explanation of inverse
square, check out the conceptual physics book. For some reason it
didn't really sink in until I saw the diagram as a pyramid one day when
I was working with a student and sitting sideways to the book. What we
are really dealing with are similar triangles. As we double the
distance from a source (the side of the triangle) we also double the
base of the triangle (the base). So where does the square fit in? We
are spreading out in width AND DEPTH, so the doubling is really double
times double, or 4 times the area. The inverse happens because the same
amount of light, photons, etc must be spread out over the area that is 4
times as great, so on each piece of area that is the size of the
original there is one fourth as much. -I can't teach without a
drawing!- Actually I created an inverse square law quilt (3
dimensional) to try to get this across to my students. It resembles the
3 tiered hanging kitchen baskets. The first level is 20 cm x 20 cm of
the brightest yellow fabric-with 36 yellow beads sewn on, the second
level is 4 20 x20 cm squares of medium yellow fabric with 9 beads on
each square, the last is 9 squares with 4 beads on each square. It
"seams" to help...