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We Asked Scientists Whether He Who Smelt it Really Dealt It

Let’s dissect this problem with physics.
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Somebody farted. It might have been you, but maybe it wasn't. We're not pointing any fingers. We weren't there when it happened. But it happened. It was silent but deadly; there was no aural evidence to indicate a culprit, so if it wasn't for the stench it would've been the perfect crime. But you smelled it, and then you turned to the person standing next to you—who was possibly a friend or maybe a stranger—and you crinkled your nose and said, "Did you just fart?"


Your friend, the fairly (or unfairly) accused, didn't hesitate to react. They didn't even pause to breathe in the toxic fumes and confirm that a Vladimir Pootin' had indeed been deployed. Instead, they just smirked and said, "Whoever smelt it dealt it."

Just like that, it's done. You've been condemned. There's no coming back from that. He might as well be OJ Simpson tugging at an ill-fitting glove. With one rhyming couplet, he's completely exonerated himself and j'accused you of a digestive felony, and there's not a damn thing you can say in your defense. We hold these truths to be self-evident: Whoever denied it supplied it. If you observed it, you served it. If you detected it, the odds are pretty good that you ejected it. It makes sense if you believe in things that rhyme. But is it true?

Let's forget for a moment whether you did or didn't fart. If you're lying and just got caught in the act of denying what you in fact supplied, that's a whole other issue. But let's pretend the knowable is unknowable, and dissect this problem with physics. Who actually smells a fart first, the person who created it, or the nearest person standing downwind?

John Crimaldi, a University of Colorado engineering professor and an expert in fluid dynamics, doesn't think there's much mystery here. "The science behind it seems fairly solid," he told us. "Firstly, odor concentrations decrease rapidly with distance from the source, so the person who smells it first is indeed likely to be the offender. Secondly, the expelled air is not only smelly, it is also hot, which causes it and the associated odors to rise after expulsion. So a likely trajectory is towards the nose of the guilty party." In other words, if you exposed it, all evidence suggests that you composed it.


But wait, not so fast. Avery Gilbert, a sensory psychologist at the University of Pennsylvania and author of What the Nose Knows: The Science of Smell in Everyday Life, says that much of what we believe about fart distribution comes from the diffusion model. (Here's a helpful video explaining diffusion and how fart smells are spread across a room.) But diffusion "describes gas dispersion under idealized conditions, with no wind and no thermal layers," Gilbert says. This is great for computer modeling, when "the stink will expand in a slow wave front in all directions from the offender. But in real life air currents tend to carry odor away in discrete plumes."

It's why the horrific odor from a sewage plant can be carried away by transverse winds to an unsuspecting town a couple of miles away. Or why if you're in rush-hour gridlock on the freeway with your driver-side window open, and there's somebody in a car ahead of you puffing on a cigarette, you're going to smell his smoke before he does. "It is entirely possible that he who dealt it is not the first to have smelt it," Gilbert says.

The problem in trying to determine where a fart's maleficent aroma ends up first comes down to context. Nobody cuts the cheese in a vacuum. "Unfortunately, you fart in the presence of the earth's atmosphere, which also has molecules in gaseous and therefore fluid form," says David Ng, a science educator at the University of British Columbia. "As a result, the direction of the fart molecules are super susceptible to the state of the fluid—i.e. the atmosphere—it's being released into." A fart is like squirting food coloring into water, he says. It doesn't necessarily go through the water as an observable stream, but will "billow before starting to generally diffuse outwards."


It's a cool way to think about farts, but it doesn't necessarily solve our methane-bomb riddle. Farts might be the great unknowable. We find comfort in claiming that he who noted it floated it. But in what direction is that noxious note actually being floated? Nobody knows for sure. It's like the Kennedy assassination "magic bullet." It's blamed for everything, but nobody can say with any certainty where it originated.

There's also a perceptive element here. Or as Gilbert calls it, "self-adaptation." It's possible, he says, for a person to become "relatively desensitized to his own odors, be they bad breath, armpit BO, or farts." So you could feasibly be surrounded by a flatulent fog of your own making and someone standing nearby could be the first to react, because you don't even recognize your farts as being an offensive redolence worth objecting to. You couldn't have smelled it first, because you're incapable of smelling your own air biscuit and declaring, "That's an objectionable odor!" If you smelled anything, it was coming from the anus of the inconsiderate asshole standing next to you.

On the other hand, "if you dealt it, you might also be more conditioned to expect to smell it," Ng suggests. "Maybe there's a special kind of cognitive bias that exists for this sort of thing, testable only by having a subject fart and another less fortunate subject strategically placed to have his or her nose closer by. Maybe this would produce evidence for a flatulence-themed version of alternative facts?"


There's clearly more research to be done, and it will involve a controlled laboratory setting in which people are farting towards other people's noses. So, you know. . . science. Or a Monty Python sketch.

Maybe both. In the meantime, you have two options here. One, you can defend yourself with a similarly ridiculous rhyme. We asked the big question—"If you perceived it, have you conceived it?"—to Bard Ermentrout, a professor of computational biology at the University of Pittsburgh, and he responded with this curious limerick.

The Navier Stokes theory shows us
The answer to what Eric has posed us
Computing the status
Of a turbulent flattus
As it diffuses on up through our noses

When we asked for clarification on what Navier Stokes has to do with ass vapors, Ermentrout sent us an email explaining that it's "a set of mathematical equations that explain how fluids such as water and air behave when subjected to different forces and perturbations. They are used to make weather forecasts, explain how pollutants spread from exhaust pipes, and presumably deduce the fate of the fart as it makes its way into the turbulent world."

Which means . . . what exactly? We're not sure. But honestly, does it matter? If you're using a mathematical equation derived from Newton's second law of motion for fluids to explain that just because you smelled it doesn't mean you necessarily expelled it, you've already entered into some really stupid intellectual territory. You've lost the battle before you even said, "Well you haven't partitioned the stress into the sum of its hydrostatic and deviatoric parts!"

The point is, you smelled something, something fetid and hateful, and that's a good thing. Was it your fart and you've been so indoctrinated with flatulent Stockholm Syndrome that you don't even realize anymore when a foul odor is released from your anus? Or did that fart originate from a hostile, North Korea-esque "other" with digestive issues, who needs to take accountability for his or her aggressive anal missile tests but won't admit to any wrongdoing? Maybe it doesn't matter—maybe you should just be grateful because you smelled it.

No, seriously: Researchers from Stockholm University revealed in a recent study that people with a diminished sense of smell were 8 percent more likely to die earlier than those with a perfectly healthy olfactory system.

Sure, that won't protect you from sneering declarations like "He who rued it brewed it" or "He who quipped it ripped it." They may have you dead to rights, but if your friend claims he or she can't smell a thing, you may still have the upper hand. Just respond with, "I may have passed gas, but at least I won't need a triple bypass." Boom, you win.

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