# How Do Flies Fly So Well? Calculus.

By Joelle Renstrom | Updated

Calculus remains the hardest class I’ve ever taken in my life. Senior year, for some ungodly reason, I decided to try my hand at AP Calculus, probably because it seemed like I should. Chemistry was fun, and even physics wasn’t too bad, so how hard could calculus be? I remember the day our teacher taught — or in my case, tried to teach — u substitution. He might as well have been speaking in Greek (or, if he wanted to be awesome, in Klingon). I had absolutely no idea what was going on, and only passed the class because of my teacher’s sympathy and my abundance of extra credit. I’m pretty humbled to learn that flies with their teeny-tiny brains can do something I never could: perform calculus, and quickly.

Cornell University scientists have been studying fruit flies. These minute creatures are ace pilots. Think about it — they’re so small, how do they withstand even moderate winds without getting tossed all around? How do they stay in stable flight? Certainly, the flight patterns of flies are disrupted all the time by any of a number of bigger forces, but clearly the flies have an efficient way of recovering. That’s what the Cornell team wanted to find out.

Researchers glued little magnets (a brush’s metal bristles snipped down to size)
to the flies and then jerked the flies around with magnetic pulses that exerted more force than most wind. I hope they gave the flies Dramamine first.

The scientists used three high-tech cameras to record the flight of the flies. The footage helped them reconstruct the movements of the flies in 3-D on a computer so they could analyze the mathematics of the flies’ technique. Basically, the flies’ nervous systems process information about the directional and durational changes in its flight pattern. It has to figure out how much the flight pattern has changed, and then how to try and correct to resume its original position in the air. This process has to happen almost instantaneously, and there’s no time for the flies’ tiny brains to perform the necessary calculations.

Instead, the flies use something called halteres, a pair of biological gyroscopes located near the flies’ wings that contain neurons capable of doing the math and communicating with the wings to fix the flight position. The calculations, which involve angular momentum, are complex, and are what we solve with calculus. How exactly the haltere neurons perform these calculations has yet to be determined, but scientists do know that if they disable a fly’s halteres, it will fall from the air.

Even if a fly’s flight pattern is disturbed significantly, scientists say that “within three wing beats that sucker has recovered completely.” Given that fruit flies move their wings 250 times per second, that means a lightning-fast course correction. Pretty impressive — and a skill that roboticists and neuroscientists will study and try to emulate for some time.