Philly Boy, Jersey Mud

In the world of baseball, every team in the Major Leagues uses something the sport has dubbed “magic mud,” muck found in a single secret location in South Jersey along the Delaware River. As it were, Doug Jerolmack, Edmund J. and Louise W. Kahn Endowed Term Professor of Earth and Environmental Science and Professor of Mechanical Engineering and Applied Mechanics, has spent his career trying to understand the mechanics of such materials.

So, when a sportswriter approached him and colleagues in 2019 to analyze the physical properties of the mud, he was intrigued. He teamed up with Paulo Arratia, Professor and Eduardo D. Glandt Distinguished Scholar in Penn Engineering; postdoctoral researcher Shravan Pradeep; and undergraduate researcher Xiangyu Chen. They explored the physics and chemistry of the magic mud to unravel what makes it so special.

Turns out, their experiments showed them that mud alters grip by reducing how slick a ball is, improving adhesion by creating a tacky film, and increasing friction just enough to help the pitcher. The researchers published their findings in the Proceedings of the National Academy of Sciences in late 2024—a win for science and for baseball.

We tell the story of the quest to understand this magic mud using a graphic-novel approach in Omnia for the first time. To maintain the experience of the piece as it appears in print, we’ve embedded it in a way that allows you to flip through it. In the bottom-right corner there’s an option to download a PDF for a more accessible version.