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Physics & Baseball: A Conversation with Dr. Alan Nathan

As Marketing Manager for Innovative Air Technologies, I have had the privilege of learning a lot about how desiccant dehumidification enriches lives. Think I’m kidding? Go eat a stale potato chip then talk to me about how much you love a crispy chip. You can thank desiccant dehumidification for that, my friend.

Part of my role at IAT is to create educational and marketing materials. As luck would have it, my most recent case study proved to be a fun and interesting one, as it involved 2 things I love. Science and baseball. Yes, I’m a nerd, I just own it.

In 2022, Major League Baseball passed a regulation that required all 30 ball clubs to store their baseballs in a consistent 70°F and 57% relative humidity. This can only be achieved in an enclosed space with precise air and humidity controls. Innovative Air Technologies was proud to serve the baseball community in providing many of the desiccant dehumidifiers for these spaces, called humidors.

As I was researching for our case study, I learned of an individual who has worked in the field of physics and baseball for years, Dr. Alan Nathan. Dr. Nathan has published many articles regarding the physics of baseball, and he graciously agreed to speak with me on this topic.

I have to be honest, this interview had me geeking out a little bit. I learned a lot of fascinating facts about how temperature and humidity can affect a baseball. I hope you enjoy reading the following highlights from my interview as much as I enjoyed chatting with Dr. Nathan.


How did you get into the physics of baseball… What got you started on that road? Ohhh that's a long story. Long ago, over 25 years ago, there was this book that actually was written in the early 90s called “The Physics of Baseball.” And… basically the story is I read the book and decided, you know, this is interesting stuff. You know, I'll spend some time myself and yeah, the story is longer than that but that's in a nutshell.

Summer Neal, Marketing Manager, Innovative Air Technologies, Covington, GA.
Download a printable version of this interview by clicking the link below.

So are you a baseball fan yourself? I am, yes.

Good deal. Now, who's your team? I promise not to judge. The Boston Red Sox.


Oh okay. I might be judging a little bit, but it's okay. We can still be friends. But I live in Atlanta, so I'm a hometown girl. Okay, so a few questions I wrote down… Did Major League Baseball consult you regarding the regulation that it passed? Yes, they did. I've been a consultant for Major League Baseball for several years now.


Baseball & Physics with Dr. Alan Nathan
Download PDF • 13.93MB

Oh okay. Excellent. So why 70° and 57% relative humidity? … How did you all come up with those numbers? Good question. So, when you store the baseball in the humidor, then… in effect, you're adjusting the moisture content of the ball, which affects... uh... primarily it affects this parameter called the coefficient of restitution. I talked about that in the in that PowerPoint, which is the bounciness of the ball. So, when the ball absorbs water, that coefficient of restitution is reduced and the ball isn’t hit as hard. If you extract water, you dry out the ball. That coefficient of restitution actually increases. The ball is more bouncy and it can be therefore hit harder. So… what Major League Baseball wanted to do was have the settings of the humidor the same everywhere, with maybe one exception, but the same everywhere. And so… they wanted the introduction of the humidor to have... They didn't want a huge change. They didn't want the effect to be huge. So, you know… if in a given location such as Arizona or Colorado, it's very dry, then raising the humidity will deaden the ball. On the other hand, if in a place like Miami, it's very humid in the summertime, uh putting it in the humidor at something like 58% will actually dry out the ball compared to what it would have been. And so they chose a temperature and relative humidity that is sort of, you know, the average of all major league cities.


So, you talk a lot about, you know, hitting the baseball. Have you done research as far as pitching the baseball? So, you know, when you store it in a humidor and you take it out, does the ball feel differently to a pitcher? Yeah, I haven't really studied that very much, but I can say several things, though. So within the, you know, another effect of absorbing moisture is the ball is a little bit heavier, but that's a very small effect. And I, I suspect that pitchers really are not sensitive to that effect. I'm just guessing. But the other thing is that generally the balls are removed from the humidor a few hours before game time. So on the other hand, it takes a long, long time for the balls to come to equilibrium with their environment. So you know, if the ball is stored at 58% relative humidity, it doesn't change very much in a couple of hours.


Gotcha. Okay. That was one of my questions. I was wondering, you know, because I think the regulation is that you can't take it out more than 2 hours before the game. I have to go back and look at my research. But I was wondering how quickly those properties changed. So I guess there was research behind that? I think I think that it takes days, not hours, but actually days for it to come to equilibrium.


Okay. So, storing it in a humidor, you know… it doesn't matter if you're in Miami or in Arizona. The outside climate, temperature, and humidity is not going to have a huge effect on the baseball during the actual game that's being played then? That is correct. Yes.


OK excellent. So, what might be looking at my questions here, you've answered a lot of them already, so I want to make sure I don't forget to ask anything. So… in more humid or less humid air that… this may be in your PowerPoint… does the ball… I guess it travels further in certain humidities, temperatures, elevations you know what causes it to travel further or less far when there's more humidity? Is it just because the ball is lighter or...? Yeah. Okay. So that's a good question. The… effect of the humidor on the flight of the ball is the principal effect… it’s that if the ball is heavier, then there's less air drag. If it's lighter, there's more air drag… so that is… I would say that there is not a huge effect of the humidor on the flight of the ball, but the actual humidity, temperature, elevation in the ballpark does affect the flight of the ball. So, it all has to do with air density. So, when the ball travels through the air, it collides with molecules of air. There are many, many, many collisions. And whenever the ball collides with an air molecule, it loses a little bit of its energy. And so, the ball because - this is the phenomenon known as air drag - and because of the air drag, the ball doesn't travel anywhere near as far as it would if the ball were just in a vacuum without air. Now the air resistance or air drag on the ball is directly related to the density of the air. So, whatever the, you know, whatever makes the air density high will increase the drag, it will reduce the fly ball distance. So, whatever makes the density low will have the opposite effect. And the air density is reduced at higher temperatures, it's reduced at higher elevations, and it's reduced at higher humidities. Now, a lot of conventional wisdom is a lot of people think it does the opposite at high humidity. But, you know, when… there's water in the air, the water molecules displace nitrogen, primarily nitrogen molecules. And a water molecule is less massive than the nitrogen molecule. So, when there's … water vapor in the air, the air is less dense. So, a baseball carries further.


Okay… Have you guys done research on how humidity affects a baseball bat? Ah interesting question. I personally have not done any research on this, but there are anecdotal stories about this. You know, so in humid weather, the the bats are made of wood … The bat is going to absorb water, making the bat a little bit heavier and batters... you know... so there's an interesting story Ted Williams you know the Ted Williams is?


The name sounds familiar yes. Okay. So, Ted Williams was one of the all-time greats in Major League Baseball. And so he played in the 40s and in the 50s for the Red Sox. And there is a story that in the summertime when it's humid he would put his bats in one of these a large industrial closed dryers to dry out … and because … he was very sensitive to the weight of the bat and he wanted it just right. And he didn't want the bat to be heavier due to absorbing water. So… it’s an effect … but I don't know if anyone's done a serious quantitative study of that.


Yes… when I found out that we made the dehumidifiers for a lot of the ballclubs, I started doing a lot of research and I thought, well, the bats are made of wood. Are we going to have a new regulation about how the bats are stored? But I guess it’s just like personal equipment, too. You know, everybody's got their own bat and how they… Yeah… the effect on the ball is a real effect. And it's … quite a measurable effect and we, “we” meaning myself and my collaborators, I referred to an article that I wrote on that experiment that we did where in a laboratory experiment where we actually measured the effect of the humidity on the this coefficient of restitution of the ball and the weight of the ball. And yeah, these are, these are measurable effects. So, you know, one of the things that's actually quite visible in Major League Baseball is effects that occur throughout the season where, you know, generally speaking it's dry in the spring, it's humid in the summer, it's dry again in the fall. And you could see those if you if you analyze the data carefully enough, you could actually see those effects. So, with the humidor, you help you help remove those effects of the ball actually changing throughout the course of the season.


Gotcha. Well, that is all is very, very interesting, I have to say. And I'm excited. I'm a huge baseball fan, so I was very excited that we were able to be a part of all of this… I really appreciate you taking a few minutes to chat with me today. Is there anything else that we didn't cover that you think would be pertinent to share? No, I think you asked all the right questions.


Well, thank you so much, Dr. Nathan. I really appreciate it. And okay. I will send you the case study when I'm all done with it. Okay. Good. Thank you. I appreciate it.


All right. Thank you so much. Have a wonderful day. Yeah, you too.



You can view our case study HERE.


Dr. Alan Nathan, Ph.D., Physics

Visit his website HERE.


















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