Collin Cunningham of MAKE produced this fun video about cymatics, the study of visible sound and vibration. As he shows, you can have a lot of fun with cornstarch, water, tone generator software, a guitar amp, and a speaker.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects