“Ant-Man” is in theaters Friday, so once again I contacted professor James Kakalios of the University of Minnesota, author of “The Physics of Superheroes” and scientific consultant to movies such as “Watchmen” and “The Amazing Spider-Man.”1 The last time we talked, Kakalios went over the real-life physics behind Thor’s hammer and Captain America’s shield. So when a movie about a guy who shrinks and can talk to ants came out, I figured there was no earthly way it could be science’d away.
I was wrong.
This interview has been lightly edited for length and clarity.
Walt Hickey: So, what does physics say about this shrinking thing?
James Kakalios: We’re made of atoms, and the neighboring atoms are all touching each other. One method of changing your size that’s out: Just squeeze the atoms closer together. The atoms in your body are already touching other atoms. The reason why they don’t just pull super close together is because as they get closer and closer, the electron clouds from neighboring atoms overlap. Electrons are all negatively charged, and similarly charged objects repel each other, and when they get closer the repelling force is really strong.
So the bottom line is, to squeeze the atoms close enough to reduce someone’s size — and keep the atoms they have — would require pressures that would definitely not get clearance from the Comics Code Authority.
WH: So playing this out mentally, you would become a human-size atom smasher?
JK: Well, an atom squisher. The atom smasher tends to just collide them once. Here you’d have to put them in the olive oil press. Then when you release the pressure, it’s not gonna be good.
The other technique that people talk about is removing mass, removing atoms.
WH: Would it just be a pile of carbon next to him every time he shrunk down?
JK: Presumably you’d want to remove them uniformly, so that you’re the size of an insect but don’t have a normal-sized brain or something. That would look very grotesque. So there’s all sorts of problems of uniformly taking them out, where do they go, how do you get them back, and that’s just getting into hand-waving stuff. We’re trying to do some serious science here, obviously.
WH: Of course.
JK: So the other option: What determines the size of atoms anyway? Physics actually has an understanding of why atoms have the size they do. They all tend to be roughly the same size. They all are about a third of a nanometer.
What determines that size? We can calculate this with quantum mechanics, and it turns out to be the ratio of fundamental constants: Planck’s constant and the mass of an electron and the charge of the electron and this and that. The thing that all these constants have in common is that they’re constant. They don’t change.
In order to change the size of an atom, what you’d need to do is — and this is where the suspension of disbelief comes in — you have to have some sort of mechanism by which you’d change the values of these constants. There’s a lot of other properties of matter that depend on these constants, in addition to just the size of an atom. If you change Planck’s constant, all the rest of chemistry gets thrown into a mess.
Not only are we magically changing the value of Planck’s constant, but we’re equally magically protecting us from all the harm that this would do aside from changing the size.
So let’s just change the Bohr radius, which is related to the average size of an atom. If you could magically do that, if you changed Planck’s constant by a factor of 10, the radius of an atom would decrease by a factor of 100; you’d go from 6 feet tall to three-fourths of an inch tall. You’re now within a factor of three of being the size of an ant. This is a mechanism by which you could see how you might change the size.
WH: What would that do to his voice? Would the relatively larger oxygen give it a sulfur hexafluoride or helium effect?
JK: That’s got nothing to do with the air, that’s just physics. Think about a pendulum that’s swinging back and forth: When you shrink the length of the pendulum it goes faster and faster; the frequency of the pendulum goes up.
Our normal speaking voice is in the range of 200 hertz, 200 cycles per second. If you shrink down to the size of an ant, if you model the vocal cords as vibrating strings, his voice will go from 200 hertz to 3,500 hertz or so. So he will be talking in this high, squeaky voice.
WH: So Paul Rudd doesn’t keep his voice when he goes down?
JK: There’s also the issue of projection; he can only force so much air out from his diaphragm. Even if the pitch wasn’t an issue, the amplitude would be decreased.
There’s another thing, his hearing would be affected. Your eardrums can be thought of as a two-dimensional vibrating surface. Our hearing ranges from as low as 20 hertz, low-frequency noise, like Barry White, up to like 20,000 hertz.
What determines your hearing range is little oscillators — namely, the cilia in your ears. They vibrate back and forth, and when they’re excited with certain frequencies they vibrate and send an electric signal to your brain.
If the cutoff is at 20 hertz, then at ant size the cutoff would be something closer to 340 hertz. And since normal human speech is at 200 hertz, below that cutoff, what happens is he wouldn’t be able to hear what you were saying. So not only is he speaking in the high-pitch Mickey Mouse voice, he’s also constantly going “What?!”
WH: Would his eyes let enough light in?
JK: The bad news is he can’t even read lips. His vision gets messed up because light is coming through the iris in your eye. The opening of your iris is maybe a few millimeters. If you shrink that down to ant size, now the size of the opening in your eye is not hundreds of times greater than the wavelength of light, now it’s less than 10 times greater than the wavelength of light.
Why that matters is because the light waves coming in are scattering off the edge of your iris and they’re diffracting and you’re getting interference effects. Everything would be fuzzy and blurred because of this diffraction effect.
This is why insect eyes do not look like human eyes. Insects have these compound eyes that are optimized to see movement.
WH: So let’s say he finally pulls off reducing the Bohr number. When he gets down there he’ll be unable to see, he’ll be unable to talk, he’ll be unable to hear. That about sum it up?
JK: He’ll be able to speak, you just wouldn’t be able to hear him, and if you could hear him you wouldn’t be able to stop laughing. His hearing would be definitely harmed; his vision would be degraded.
WH: All this without talking his ant-control powers. The global biomass of ants is somewhere from like 9 percent of the human biomass to like 85 percent.
JK: Ants can be very highly specialized, perform lots of different functions. They do tend to work with a hive mind. To some extent, they do things that one would not be able to ask other people to do. [Ants] quickly sacrifice themselves to save others — you ask them to do various tasks, and they throw themselves into it.
WH: I think Ant-Man has it all wrong. His real superpower is controlling a biomass larger than any army on Earth, not messing with physics to potentially destroy himself.
JK: One of the main ways they communicate is by excreting a chemical and then detecting it with his antennas, and how Ant-Man is doing that …
WH: Seducing them with pheromones?
JK: Regardless of how information enters our brain, whether we read it, detect it with our eyes, hear it with our ears, at the end of the day it’s converted to an electrochemical signal. That is then processed, and we translate that into information or noise or what have you.
Presumably he’s communicating with ants because he’s figured out what those electrochemical signals are once they detect the pheromone. And then he’s broadcasting a powerful electrochemical signal that overwhelms whatever’s going on inside the ant’s brain.
WH: I like that better, I’m going to stick with your explanation.