Subtle changes in the hearts of baseballs might help explain why the number of home runs has surged in Major League Baseball since June 2015, Chemical & Engineering News reports. Using tools including scanning electron microscopy, x-ray spectroscopy, and thermogravimetric analysis, researchers reported in ACS Omega in late 2019 that the cores of balls used in 2016 and 2017 were less dense than those in balls used from 2014 to June 2015. (June is when the league takes a brief break for the All-Star Game and teams restock their supplies of game balls, which are made by a single company, Rawlings.) The slight decrease in density likely doesn’t entirely explain the increase in long balls, the researchers say, but it could have contributed to the trend by making the balls bouncier.
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