News & Features

Alan Nathan

A Few Minutes With Alan Nathan

At the Sapora Symposium, University of Illinois emeritus professor of physics Alan Nathan speaks with College of Applied Health Sciences media relations specialist Vince Lara about his research on the physics of baseball.

Click here to see the full transcript.

VINCE LARA: This is Vince Lara at the College of Applied Health Sciences at the University of Illinois. Today I spend a few minutes with Alan Nathan, emeritus professor of physics at Illinois, and renowned baseball physicist. Alan recently gave a presentation at the Sapora Symposium on the campus of Illinois.

Alan, Rob Arthur, who you know, recently wrote about the baseball-- "Did they dejuice the baseball? Did they rejuice the baseball? The answer is both, depending on the day." I'm wondering what your opinion is.

ALAN NATHAN: Well, the thing that Rob did was he looked at so-called drag coefficient. So it's a measure of how much speed the ball loses as its going through the air. So it's a very important factor for fly balls. The more the air drag, the less likely it is to be a home run. Turns out, you can measure these things actually very, very well, just with all of the pitching data that we have from Statcast. We have thousands and thousands and thousands of pitches that we can analyze, and if you look over the last couple of years, and even within any given year, you see a lot of fluctuations up and down of this quantity, suggesting that the ball itself is quite variable from one ball to the other, and you see changes from year to year. So for example, in 2018, the drag was somewhat higher than it had been in 2017. The ball didn't carry as far, and consequently fewer home runs. Things reversed again in 2019, where the drag was down-- home runs were up. And then the post-season happened, and home runs are up, home runs were down, and then they were up, and it became a rather confused situation. I think it's probably fair to say it's still a somewhat confused situation. Although one thing I would say about the postseason, of course-- you have fewer games being played than on a typical day during the regular season, so you sort of have to take that into account. But--

VINCE LARA: And better pitching, too.

ALAN NATHAN: And better pitching, colder weather on the average. I mean, there are all kinds of things you have to take into account.

VINCE LARA: Mm-hmm. OK. You know, Rob also wrote at the beginning of this season, that the ball had lower drag, and that was something that was later corroborated by MLB officials. Your 2014 study however, found that the primary reason for variation is due to a difference in the drag properties of different types of baseball. And there's even variation within a given type. So are you talking about the seam height, or are you talking about the inside of the ball, are you like-- what sorts of things were you looking at in that study?

ALAN NATHAN: Yeah. Well, the study that I did in 2014 was entirely simply looking at trajectories of baseballs, and measuring how far they'd gone. We didn't dissect the ball or do anything on the inside of the ball. What we did do is we did measure the seam height, and we found that there was a definite correlation between the seam height and the drag. So the higher the seams, the more drag, the less well the ball carries. We found that particularly when looking at different types of balls. So at the time, the NCAA was using a raised seam baseball. They have since switched to a flat seam baseball. And we definitely found that that raised seam baseball simply didn't carry as far. In fact, the fact that the ball didn't carry as far led the NCAA to switch to a flat seam ball, to basically get more home runs.


ALAN NATHAN: So we didn't look at the interior of the ball, we didn't look at the seams. Now in our initial study from Major League Baseball, which took place in 2017-- the report was issued in 2018-- we were looking at the home run increase over the 2015-17 period, and we found you could pretty much attribute all that increase in home runs to drag. However, we really were not able at that time to figure out what exactly changed in the ball that would lead to more drag-- or less drag, and therefore more home runs. Now for sure it's true that, as I said, the drag was up, homers down in 2018, and the reverse in 2019. The home committee of Major League Baseball sort of got back into action around mid-season this year, and we're--

VINCE LARA: Which you're part of.

ALAN NATHAN: Which I'm part of. And we are getting close.


ALAN NATHAN: We're getting close to the point where we're going to go public with our findings.

VINCE LARA: Interesting.

ALAN NATHAN: I can't talk about it, what they are, but we're getting quite close to that. Hopefully maybe at the Winter Meetings, which will be in a few weeks.

VINCE LARA: OK. You know, Rob Manfred has said-- and Rawlings has said-- that the baseball recipe remains the same, regardless of year. However, Meredith Willis, who you also know, and Rob Arthur concluded this year that ball construction was different, including lower seam height. Do you have any insight into that? Like, how that happens? If baseball's saying it's not-- you know, baseball's saying that the recipe is the same.

ALAN NATHAN: Well, for sure. I believe it's true that the recipe is the same. I mean, I really do believe-- I visited the plant in Costa Rica where the balls are made a couple of years ago. We've talked extensively with people from Rawlings. There are changes that are made, but largely due to the fact that you're dealing with organic materials-- wool, leather, cotton-- and there's variation in those materials. So-- but the process really hasn't changed. There could very well be differences from one ball to another within a given year, differences in average properties of the balls from one year to another, and that's just a natural consequence of the materials that are used and the actual process that's made. I mean, there's a lot of hand work that's done to create a baseball, particularly sewing the cotton threads through the leather on the outside-- that's all done by hand.

So for sure, Meredith Wills has taken some balls apart, she's found differences from one year to the next. Her latest article came out, in fact, just yesterday, and she looked at the postseason balls, and-- OK, she drew some conclusions there. What she hasn't done-- because she really has no way to do it-- is to show in any conclusive way that whatever changes she does see actually affect the drag on the ball. That is something that we, our group, is actually uniquely able to do, because we can take baseballs-- we have large samples of baseballs, we can take them into the laboratory, we can measure their drag with very, very high precision, much higher precision than you can actually measure by tracking pitches in a ballgame. And we can measure seam height very accurately, we could measure the roundness of the ball, we can measure the thickness of the seam, and the surface of the ball. I mean, the drag is largely a surface effect. It's the air interacting with the ball, and the only thing the air sees is the surface of the ball. So you know, you could pretty well isolate it. Is it-- to be something associated with the leather, the smoothness of the leather, for example? Or something to do with the seams? And if you look at a baseball, there's a lot of little holes there in the leather, and the seams are sticking up, and there's a lot going on there, and no one has been able to model this from a fundamental physics point of view from First Principles. So ultimately, you're stuck with just doing the best measurements you can, which is I believe what we're able to actually do.

VINCE LARA: Now, the very fact that Major League Baseball has your committee, and the very fact that you looked at things like a humidor in the Diamondbacks’ park in Chase Field, says to me that Major League Baseball is concerned about this explosion of home runs. Now--

ALAN NATHAN: I have no inside information.


ALAN NATHAN: I don't question people's motivations at all, so I can't say what's on their mind. I don't interact directly with Rob Manfred.


ALAN NATHAN: I do interact with the people I interact with-- Reed MacPhail. MacPhail's a famous name in baseball, this is the fourth generation MacPhail.

VINCE LARA: OK, fourth generation.

ALAN NATHAN: And Morgan Sword is the other person I interact with. And I can tell you, from having talked with him extensively, that-- I don't know what their bosses are thinking, but they for sure are very concerned.


ALAN NATHAN: And I can also say that having--

VINCE LARA: Are they concerned because it's affecting the integrity of the game?

ALAN NATHAN: I guess-- I don't know. Look, I don't want to characterize why they're concerned. I know they're concerned. I mean, maybe they're just concerned because they're getting a lot of bad publicity, I don't know.

VINCE LARA: Right, right.

ALAN NATHAN: But they are concerned. And I know Rawlings is concerned. I think Rawlings is largely concerned because of bad publicity.


ALAN NATHAN: They really don't like all the bad publicity they're getting, and sometimes they're even a little defensive about it. But all by way of saying, that I think they're-- I believe, personally, that they're all honest brokers, that they really are-- for whatever their reasons-- are trying to figure out why there is an increase in home runs. If the ball has changed, what has changed? How can we, going forward, better control the production of the ball? And I really do believe that they are genuinely concerned about that, but I don't know their motivations for being concerned.

VINCE LARA: I'm going to ask you something that I asked Charlie Young, who was on an earlier podcast. Which came first for you, your love of baseball or your love of physics?

ALAN NATHAN: It's an interesting question. So I like to tell people that I have been a physicist all of my professional life. I've been a baseball fan virtually all of my life. Now, it is true that I had a long career as a nuclear physicist-- faculty member here at the University of Illinois, teaching physics, doing research. And it was really well into the game that I got interested in baseball. So although I've-- in applying physics to baseball, I've been interested in baseball, but in the specific job of applying physics to baseball, it's been much more recent. It's been over 20 years, but still I was well into my career when that happened.

VINCE LARA: What sparked that?

ALAN NATHAN: Interesting question.


ALAN NATHAN: There's actually an interesting story. So the physics department has this outreach program where we give talks on Saturday mornings-- used to be for high school honor students, but now they've opened it up to the public, they call it Physics for Everyone. And way back in 1997, it was my turn to give a talk. And normally the faculty talk about their research but they present it in a way that the general public can understand it. So I was thinking of doing something like that, but then there was this book called The Physics of Baseball, written by another physics professor, that I had had in my bookshelf for about five or six years. I bought the book, I thought I'll do this one someday, but I never read it. All right, so then I said, you know, I'm going to talk about the physics of baseball, which will force me to read the book, and I'll learn something and it'll be a one shot deal but it'll be kind of fun. And it would have been a one shot deal, never to be returned to, except that there was a News Gazette reporter in the audience who interviewed me afterwards, wrote it up in the front page of the Sunday paper, and then everyone started calling me up to give talks, and this and that, and then it just sort of blossomed from there.

VINCE LARA: My thanks to Alan Nathan. This has been "A Few Minutes With."

back to news