"This then led to the half of the Sophisticated Shadows exhibit where you can see that a shadow is a missing image.
"The shadow of a butterfly or the shadow of an airplane, if it's high enough, is actually round because it's blocking an image of the sun. Here's a sort of positive way to show that. Through all these holes in the outline of the plane, you have an image of the sun going through each place. Now if I pull this back farther and farther, the images of the sun keep getting bigger and bigger, but their centers never get any farther apart. So at some point, when you get back far enough, each one of these images of the sun will be so big that they'll resolve into one large image of the sun.
