On Monday, September 15th, 2025, MLB Marlins coach and former JILAn, Dr. Aaron Leanhardt, gave the first Life After JILA talk of the fall semester, with a record-breaking turnout for the seminar series. Over 60 JILAns, including PIs, graduate students, postdoctoral researchers, and undergraduate students, attended Dr. Leanhardt’s talk about his journey from academia to professional baseball. Dr. Leanhardt got his PhD from MIT and then joined the Cornell group as a postdoc in 2003, staying until 2007 when he became an Assistant Professor at the University of Michigan. After 7 years as a professor, he left academia to coach baseball, landing a job in the Yankees' minor league system in 2018. After working with the Yankees for 6 years in various coaching roles, he started as the Marlins' field coordinator for the 2025 MLB season.
Dr. Leanhardt started his baseball career much earlier than 2018, playing in a recreational softball league with other JILAns while he was a postdoctoral researcher. He chose 19 as his jersey number for the league because it is the atomic weight of fluorine, and, at that point, the Cornell group was using the hafnium fluoride ion to measure the electron's electric dipole moment. His current Marlins jersey number is also a reference to his postdoctoral research; 72, his number, is the atomic number of hafnium. He joked that he would change his number to 90 if the Cornell group beat the limit on the error in the electric dipole moment with Thorium, earning a loud laugh from the audience.
Near the end of his time with the Yankees, Dr. Leanhardt developed the torpedo bat, an innovative design that puts the largest part of the bat in the middle, where the player hits the ball. Crucially, the torpedo bat weighs the same as a standard bat, as required by MLB regulations, which has led to its adoption by many players in the league. At the beginning of the 2025 season, Dr. Leanhardt switched teams, becoming the field coordinator for the Miami Marlins, where he develops drills to help players improve their performance. He analyzes game and training data to help identify skills that need improvement and then uses physics education research techniques to devise creative exercises to communicate those skills to the players. During the talk, he referenced different physics experiences he brought to baseball, making analogies to concepts such as an overdamped spring.
During the Q&A, Dr. Leanhardt was asked multiple times about his journey from physics to baseball. One attendee asked how JILA compares to the MLB, and Dr. Leanhardt explained how both jobs involve problem-solving, but that they focus on distinct types of problems. He also used the Q&A as an opportunity to teach the audience some baseball slang, explaining the term “standardized mud,” which refers to the league-approved type of mud that pitchers rub on the baseball, or “pearl,” before pitching. After many questions and lots of laughs, Leanhardt joined some attendees at the Sink, where he shared more about his career path from physics to baseball.
Written by Emma Nelson, JILA Graduate Student