For the love of baseball—and physics!

Bill Bell
for Illinois Physics

Illinois Physics Emeritus Professor Alan Nathan’s office sits in the middle of a nondescript hallway on the north side of Loomis Laboratory. Stopping in front of the door, I notice a Boston Red Sox sticker with his name on it. Those who aren’t familiar with Nathan could guess at the very least that he likes the Red Sox. Entering his office, they’d quickly realize that “likes” is an understatement.

“There’s a tremendous amount of subtlety to the game of baseball. It looks simple on the face of it. But if you try to explain the rules of the game to someone who’s never watched it before, you realize how subtle it is. It’s that subtlety that I find the most charming part about it.”

Everywhere you look is baseball memorabilia. To the left, wooden baseball bats lean against the wall under a chalkboard. To the right are a couple baseballs, one in a cup, one rolling around the desk. Hanging on the back wall is a 2018 Boston Red Sox World Series Championship banner.

And in the center is Nathan, sitting in his swivel chair with his legs crossed, his right arm propping his chin up from the arm rest. He confidently answers a series of questions he’s probably been asked at some point before. It’s not the first time he’s been asked to communicate his expertise in the physics of baseball in an interview.

But before too long, one of my questions catches him off guard: “Why do you love the game of baseball?”

It seems an obvious enough question—Nathan’s office decor clearly illustrates that he loves the sport. A lot. And everything he has shared points to the same thing: Nathan’s passion for the game has driven him to research baseball in its closest details for over a quarter-century.

Nathan sits back in his chair and looks up at the ceiling, as though pondering a complex physics problem. He noticeably takes more time to craft this response.

“There’s a tremendous amount of subtlety to the game of baseball,” Nathan proffers. “It looks simple on the face of it. But if you try to explain the rules of the game to someone who’s never watched it before, you realize how subtle it is. It’s that subtlety that I find the most charming part about it.

“The fact that no two baseball stadiums are alike—I find that fascinating. The fact that you can do a statistical analysis on a particular question, and there’s a lot of noise in that analysis—finding the signal among all the noise is an interesting kind of problem.”

Solving these kinds of problems has made Nathan one of the leading experts in the country on the physics of baseball. Over the years, he has been interviewed countless times, for news articles, podcasts, video series, and TV.

The ball-bat collision

So how did it all begin? Before Nathan was heading Major League Baseball (MLB) research committees and working on baseball’s most pressing physics questions, his research focus was experimental nuclear physics. He joined the faculty at Illinois Physics in 1977.

It wasn’t until just before the autumn of 1996 that Nathan began researching the game’s physics. The Rumford, Maine native reviewed work being done by early pioneers in the physics of baseball for a public lecture he gave as part of the Saturday Physics for Everyone series, titled “When Ash Meets Cowhide: The Physics of Baseball.” Nathan had come across a seminal 1991 article by the late Purdue University Physics Professor Lonnie Van Zandt and was intrigued. He began reading the paper, all the while trying to derive the same results himself—which he was able to do, up to a point.

“I worked through all the details of the Van Zandt paper that treat the bat as a dynamic object that is capable of vibrations,” Nathan recalls. “I then worked out an extension of his work to include the effect of those vibrations during the ball-bat collision.”

In response to Van Zandt’s paper, Nathan published an article accounting for energy conservation in the calculations.

“The initial energy of the ball coming off the bat must go somewhere, whether some of it goes into the ball, or some of it goes into the bat,” explains Nathan.

Switching up the rules

Nathan’s paper on ball-bat collisions garnered some public attention and led to Nathan being asked to serve on an NCAA committee tasked with establishing techniques for regulating the performance of aluminum bats.

“This involved understanding what makes aluminum bats perform better than wood bats, a problem well suited to a physics-based analysis,” notes Nathan. “Once those differences are understood, coming up with a performance metric that can be used to regulate the bats is straightforward.”

The committee met once or twice a year, and Nathan was for the most part working independently on his research into the matter, having an occasional phone conversation with other committee members on technical aspects here and there. It happened that the other members of the committee were taking a different tack than Nathan, one that wouldn’t provide the clarity needed to write the NCAA regulations.

“They had already gone off in a certain direction, and the more I thought about it, the more I felt like that was the wrong direction. It’s not that they were wrong, it was more that it was more complicated than it needed to be,” Nathan remembers. “So, I steered them in another direction, proposing a new technique and some new analyses. And in the end, we advised the adoption of a different performance standard than the one that was used at that time. I wrote a detailed position paper on the subject and distributed it to the members of the committee. Ultimately, the committee thought it was a good idea.”

The NCAA Baseball Rules Committee also thought it was a good idea. The new bats, which are now used in both the NCAA and high school baseball, must adhere to the so-called “BBCOR specification,” which essentially makes aluminum bats perform similarly to wood bats.

“It seems to have stood the test of time,” notes Nathan. “This work was done in 2008, and 16 years later, they’re still using it.”

A new data source and new connections

Another major vein of Nathan’s research into the physics of baseball began in 2006, when the PITCHf/x pitch-tracking system was first introduced by MLB. The technology employed cameras to measure the full trajectory of every pitch, providing real data for analysis, such as velocity, position, and break.

The new technology piqued Nathan’s curiosity. In fact, he was so intrigued by Sportvision’s innovation that he reached out to the company. He discovered that the brains behind the system, Marv White, received his bachelor’s degree from Illinois Physics in 1969. Nathan recognized that he wasn’t the only one who had taken the initiative to study the data the pitch tracker was generating in an attempt to understand what the device was teaching them—and the new technology was calling for specialized input.

“There were all kinds of people during the 2007 season who were doing analyses of the data—I was doing some, and other people were doing some. That led me to the idea we should have a conference devoted to just this topic. I proposed the idea to Marv White, and he agreed to sponsor it,” Nathan shares. “It was a great opportunity—I was talking to baseball people, including people from Major League teams.”

Nathan attended the conference on the pitch tracker system over the four years it was held, publishing several articles in that time.

“They were absolutely superb experiences,” Nathan says of his work with the pitch-tracker conferences. “These meetings were highly focused and just a lot of fun.”

A proliferation of home runs

More recently, Nathan’s physics-of-baseball research has focused on a question that had baffled MLB officials: what caused the increase in home run rates in the 2015 to 2019 seasons?

It was in 2017 that Nathan received a phone call from an unfamiliar area code. He didn’t hesitate to answer—at this point, he was regularly getting inquiries from across the country. Never could he have imagined the opportunity being offered from the other end of the line.

Morgan Sword, MLB’s senior vice president in charge of league economics and operations, was calling to ask Nathan to chair an MLB committee to investigate the increase of home runs over the previous three seasons.

“When they asked me if I wanted to chair the committee, it was like, ‘Yeah, yeah, twist my arm more.’ Yeah, how could I not be interested in chairing this committee? It’s almost like this whole problem was created just for me. I really felt that way,” Nathan says.

Nathan’s task on the committee wasn’t to analyze the data. He says there were members better at digging into the data at a more efficient rate. Where Nathan excels is in interpreting the information.

Others brought him their findings—a year’s worth of data and research—and he stitched the results together to find their significance. It took him over a month to compile the findings into a report sent to MLB on December 31, 2017—the deadline given to the committee.

So, what did the report say?

“We figured out that it wasn’t the launch conditions that had changed. They stayed on average the same. It was how the ball carries through the air that changed,” Nathan explains. “We determined that the so-called drag coefficient is the thing that had changed, and we measured how much it changed. To draw the connection to how the change in drag coefficient affects the change in home runs is a physics problem. My major contribution was showing that the change in drag coefficient was consistent with and could explain the change in home runs. This was the crowning achievement of the project.”

But there’s more to the story. As Nathan explains it, “As often happens with research, problems get solved and new problems get uncovered. The solved problem is that the changes in home runs could be explained by variation of the drag coefficient of the ball.  The new problem is that we can’t really figure out how two baseballs that look and feel essentially identical could have different drag coefficients. It almost certainly has to do with subtle features of the seams, but we haven’t been able to figure it out yet. That work is ongoing.”

When Nathan talks about his work with MLB, he perks up in his seat and smiles constantly.

“You know, when this home-run increase happened and I got the call, I was almost too willing to chair this committee—and why not? For me, this is the dream job. The two major things I’ve worked on are the physics of the ball-bat collision and the physics of the flight of the ball through the air, and this involved both of those. It was definitely a fun project to work on.”

Mentoring the next generation

In addition to his work with baseball organizations, Nathan has mentored undergraduate students in the physics of baseball. One such student, then-freshman Charlie Young, contacted him in 2016 about working on various projects on the physics and analytics of baseball. Over the next four years, Nathan and Young grew from mentor and mentee into equal coworkers and wrote several papers together. Nathan connected Young to Illini baseball coaches, leading him to organize a group of like-minded undergraduates to do baseball analytics for the team. Young now works as an analyst for the Houston Astros, and he even has a World Series ring.

Currently, Nathan is working with physics major Riku Komatani, who is on the same trajectory. He will graduate in May and shortly thereafter begin working with the Seattle Mariners. Comments Nathan, “Needless to say, both experiences have been personally very rewarding.”

Nathan admits that when he first started researching the physics of baseball, it wasn’t to benefit the baseball fans or to have an impact on the Major Leagues—it was really for himself. He wanted to understand the sport in all of its subtleties.

In the intricacies of baseball’s physics, Nathan’s love of the sport has evolved into something far more than what he could have imagined, and this is what pushes him to continue trying to unlock the mysteries of baseball.

“I started doing this for my own interest. And I went many years doing this because it was fun and interesting for me to do. No one was paying me to do it. They are now,” Nathan laughs. “But I was just doing it as a little side hobby in addition to all the other little things I was doing. So yeah, I never thought it would lead to this at all.”

“At some point, I’ll stop doing this,” Nathan adds.

Is that what he tells himself?

“It is inevitable. And I would certainly like to think that when I’ve finished doing this, I have either dropped dead or moved on to something else—and that I have made useful contributions to the sport.”

For more information about Nathan’s research in the physics of baseball or to learn about the pioneers of this field, please visit his homepage on the Illinois Physics website.