World Cafe Live
3025 Walnut Street
Philadelphia, PA 19104
Earth and Environmental Science, University of Pennsylvania
“The Secret Life of Pebbles: how the history of Earth and other planets is encoded in pebble shape”
Rounded pebbles in rivers and beaches are as common as they are admired. Stunningly, similarly smooth pebbles have also been discovered on the surfaces of Mars and Titan. How do pebbles get this way, considering that they are born as angular fragments of broken rock? While this question was first pondered by Aristotle, an answer has only begun to emerge in the last decade due a surprising confluence of abstract mathematics, experimental physics and field geology. In this talk I consider the life cycle of a pebble, and show how its ‘maturity’ can be determined from its degree of roundness. I explore how progress on this esoteric problem informs our understanding of the early solar system, and current environmental issues.