Last modified 9/15/08

Plenary Lecture

Shadow geometry

presented by

Stephen Robinson

Professor of Mathematics and Department Chair
Wake Forest University
Winston Salem, NC

Abstract: Suppose that you use a flashlight and a rectangular card to cast a shadow on the wall. Outline the shadow, especially the corners, with bright markers and then set the card and the flashlight aside. Now bring a friend into the room and ask them "Can you tell me where the flashlight and the card were when I created this shadow?" How can your friend solve the problem? Will two different friends find the same solution? What if you were to cast the shadow of a three-dimensional shape like a cube instead? In this talk I will describe some of the wonderful ideas of Projective Geometry that are motivated by problems such as this. I will also describe an important medical application. All levels of mathematical preparation are welcome.

Given shadow.   A solution to the problem.