Hey Rockstars,

First, I need to acknowledge that while last week I was ranting about my love for Anakin Skywalker, today I’m talking about my fascination with the physics of bee flight. What can I say? I’ve got a lot of interests.

I think many of us are familiar with that quote that is supposedly on a NASA poster that “Aerodynamically a bee’s body is not made to fly; the good thing is that the bee doesn’t know.”

Or if not that quote, then maybe you’re familiar with the Bee Movie where the opening line is quite literally: “According to all known laws of aviation, there is no way that a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway. Because bees don’t care what humans think is impossible.”

And you know what, it’s true: bees don’t care about what humans think is impossible. But also, it’s not true.

Still, this quote has made me recently fascinated by bees. I have learned enough about bees, the intricate social hierarchy of the hive, and the waggle dance through The Magic School Bus, thank you very much.

No, I’m fascinated by the fact that a tiny insect can flap its wings approximately 230 times per second and somehow stay suspended in midair. Just in case your eyes glossed over that number: two hundred and thirty times. Per second.

I rarely think about bees flying. In fact, if I’m thinking about bees flying, it’s usually because I’m trying to shoo one away without swatting at it, because I’d prefer not to anger it and get stung in the process. But, recently I stumbled upon an article called How Bees Fly (The Physics That Took 70 Years to Figure Out), and I have now spent an unreasonable amount of time thinking about bee aerodynamics.

This is what happens when I have access to the internet and something catches my attention. I start with one innocent question, and suddenly I’m reading about fluid dynamics and the mechanical properties of insect flight muscles. What can I say? I’m a physics girlie.

So, naturally, we’re going to talk about bees.

But first, we need to address the idea that bees shouldn’t be able to fly according to the laws of aerodynamics. Because, as it turns out, bees have been obeying the laws of physics this entire time.

The story goes back to the 1930s, when French scientists Antoine Magnan and André Sainte-Laguë tried to calculate how insects could fly using aerodynamic principles associated with airplane wings. And the calculations didn’t work. Based on their assumptions, insect wings appeared unable to generate enough lift to keep the animals airborne. Then explain something to me, Magnan and Sainte-Laguë: how were the bees already flying?

But the real problem was that the mathematical model wasn’t describing what bees’ wings are actually doing. While an airplane generally generates lift by moving its wings forward through the air, a bee’s wings are sweeping back and forth, rotating, changing their angle, and interacting with air that has already been disturbed by previous wingbeats. The airflow around them is constantly changing.

It took advances in high-speed photography, experimental techniques, and computational modeling for scientists to understand these movements in much greater detail. And in 2005, researchers at Caltech published a study that helped explain the particular way honeybees generate the aerodynamic forces needed to fly. The researchers actually built a large mechanical model of a bee’s wing so they could measure the forces generated during different parts of its movement.

When a honeybee hovers, its wings beat at roughly 230 times per second, sweeping through a relatively short arc of about 90 degrees. And rather than generating all their aerodynamic force in one smooth motion, the wings produce important forces at different points throughout each stroke, including when they reverse direction.

The wing also interacts with tiny swirling structures in the air, called vortices, created by its motion. A vortex is essentially a region where air swirls around an axis. A particularly important one is called a leading-edge vortex, which forms near the front edge of a moving wing and helps generate lift. Honeybees are especially interesting because they generate important aerodynamic forces throughout their wing strokes, including at the moments when their wings reverse direction.

So while we see a little bee suspended in front of a flower, the bee is moving its wings through an extraordinarily complicated sequence of sweeps, rotations, and reversals, generating and responding to aerodynamic forces that we can’t even see.

For context, 230 times per second means about 13,800 wingbeats in a minute. One complete wingbeat takes approximately 4.3 milliseconds. By the time you’ve finished reading this sentence, a hovering bee could have completed hundreds of wingbeats.

But then I started thinking about the cute bees that are hovering near flowers, and it was only then that I started thinking about what hovering actually requires. The bee has to keep generating enough upward force to support its own weight, continuously adjusting its movements to remain stable. And the fact that the bee isn’t going anywhere makes the whole thing look deceptively effortless.

Hovering can demand substantial energy, and unlike an airplane gliding forward, the bee cannot rely on its forward motion to keep air moving over its wings. It must generate the forces it needs through flapping. There are different energetic costs associated with different kinds of flight, but hovering is certainly not the equivalent of taking a little break.

Which brings me to the title of this essay: bees don’t loiter.

I mean, sure, they physically can remain in one place in the air, but I highly doubt they’re just hanging around doing nothing. Then again, I don’t know any bees to ask them directly. The entire time they’re suspended in front of a flower, their wings are beating furiously, their muscles are oscillating, and they’re managing the aerodynamic forces required to remain exactly where they are.

And if the conditions change, the bee can adjust.

In fact, researchers tested this by having honeybees fly in a mixture of helium and oxygen, which is less dense than ordinary air. Instead of beating their wings substantially faster to compensate, the bees increased the distance their wings traveled during each stroke. Their wingbeat frequency stayed relatively consistent, but the angle through which their wings swept increased from about 91 degrees to 132 degrees. I would have assumed that needing more lift meant flapping faster, but it turns out there’s considerably more to bee flight than that.

The more I read, the more amazed I become that this is happening all around us, all the time. We’ve been watching bees fly for as long as human beings have existed, and for most of that time, we had no idea how much was happening in those tiny movements. There are so many everyday phenomena that I accept without giving them a second thought. A bird takes off. A bee hovers. A dragonfly changes direction in midair. A hummingbird sits on my mom’s hummingbird feeder and drinks the sugar water. I see these things happen, think, “Wow, that’s beautiful,” and then go about my day. The explanation was always there, in the movement of the wings. We just had to figure out how to see it.

Anyway, the next time you see a bee suspended in midair, consider what’s happening in those few seconds. It might look like it’s just hanging around, but there’s an extraordinary amount of physics involved in staying exactly where it is. And if someone tells you that bees shouldn’t be able to fly according to the laws of physics, you can tell them that the bees are doing just fine.

Until next time!

xo

Sandhya

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