Changes in baseball chemistry could contribute to rise in home runs

Home run rates in Major League Baseball (MLB) games increased by over 60% between June 2014 and June 2019—prompting fans, players, and researchers alike to question whether the balls were deliberately altered, or “juiced.” Chemists have now cracked the balls open to see whether changes to their cores have helped them fly farther. Computed tomography scans and other analytical techniques revealed changes in the density and composition of the cores that could partially explain the surge in homers, though more research is needed to solidify any connection (ACS Omega 2019, DOI: 10.1021/acsomega.9b00405).

In 2018, ESPN asked scientists at the University of Southern California’s Keck School of Medicine to look inside the balls using computed tomography scans. The researchers scanned four baseballs used in MLB games between 2014 and the 2015 All-Star Game and found that the cork cores were 56.7% denser than four balls used through the 2017 season.

Building on this finding, Soumitra Basu’s group at Kent State University, led by then-graduate student Nathan Beals, turned to trusted chemical techniques like scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis. They determined that the newer baseballs were more porous than the older ones and contained about 10% less silicon.

A less dense, more porous core could make the ball bouncier and increase its speed off the bat, Basu says. Meredith J. Wills, a data scientist working in ball- and player-tracking at SportsMEDIA Technology and who was not affiliated with the study, agrees. She says that additional experiments are needed to match the chemistry to the physics.