From: Ben Pittenger (benpittenger@earthlink.net)
Date: Tue Jun 11 2002 - 08:05:18 PDT
Date: Tue, 11 Jun 2002 08:05:18 -0700 From: Ben Pittenger<benpittenger@earthlink.net> Subject: Eclipse fun Message-ID: <Springmail.0994.1023807918.0.46393200@webmail.pas.earthlink.net>
Yesterday afternoon I had the usual gathering of folks around the pinhole camera we made. Another neighbor brought out a welding mask (which I still don't fully trust. What is the word on whether these are safe? I ended up looking only for a short time, and even then, I tilted it to look through as long a cross-section of glass as possible, and to achieve as much reflection as possible. Is this just paranoia? Are these okay for viewing the sun? For how long?).
What I found most fun was observing pseudo-pinhole cameras, like projections through shadows of trees and through small holes made with our fingers and hands. The little sections of light that made it through the leaves of trees were all crescent moon-shaped (or would it be crescent-sun shaped?) It totally changed the overall sense I got of the tree's shadow! I got much more of a linear and parallel impression of the overall shadow, due to the elongation of the solar crescent images on the horizontal street. Talk about changing perception! Did others get a different sense of these shadows?
This all was experimental confirmation of what I remember Paul and Eric & co. telling us about in one of our workshops on physics during my summer new-teacher workshop - that the little round light spots in shadows of treas were really projections of the sun.
One thing (of many) I haven't come to understand yet, though, is how this phenomenon works when the various leaves aren't in one plane that is fairly perpendicular to the track of the sunlight. A regular pinhole camera has a (fairly) neat round hole in the plane of the tin foil or cardboard. But light through a tree passes leaves that are separated along the path of light by centimeters or meters. It just surprises me that the image can project fairly clearly through a "hole" of this sort. The explanation that the distance between the leaves is small compared to the distance from the sun popped into my mind, but the distance is large compared to the wavelengths of the light.
I also got some good projections on our wall by playing with our mini-binoculars - from both ends!
I hope everyone else had so much fun viewing!
Ben
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