Why does a female jogger's ponytail sway side to side when the motion of her body is up and down? And why is it so difficult to pour tea from a pot without dribbling some on the table? These are the sorts of questions that occasionally preoccupy Joseph Keller. For his efforts to elucidate the mysterious forces behind these everyday conundrums, Keller, an emeritus professor of mathematics and mechanical engineering, has been awarded not one, but two Ig Nobel Prizes. Bestowed annually by the editors of the tongue-in-cheek Annals of Improbable Research, the awards "celebrate the unusual, honor the imaginative—and spur people's interest in science, medicine and technology." Keller shared the 2012 physics prize for his 2010 paper, "Ponytail Motion," which explains that while ponytails could bob up and down, "that's unstable if the jogging frequency is twice the pendulum frequency," as it is for most runners. He was also retroactively awarded the 1999 physics prize for his contributions to the paper "Pouring Flows with Separation," in which he calculated the optimal curvature for a teapot spout to eliminate drips.
