Title: Can one hear the shape of a drum?<br><br>

Abstract: The title is stolen from a famous 1966 article by Mark Kac, based on a talk he had given to the MAA/AMS. The article spawned a rich literature on inverse problems in mathematics and I will describe a little of this. Kac's question was finally answered negatively by Gordon, Webb, and Wolpert in 1992. I will raise some questions about their answer, as well as Kac's theorem that even if you cannot hear the shape, you can, at least, hear the size of drum.