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Why Does Toilet Water Move When It's Windy Outside?

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Reader Erin from Baltimore wrote in wondering why the water in her toilet bowl moves on windy days. This is one of those questions – like the one Jason asked about his dog’s popcorn-scented paws – that makes me pause and wonder if I’m getting trolled, or if I’m missing out on a strange phenomena that everyone else seems to be aware of.


So, I did a little Googling and even hung out in the bathroom staring at the toilet bowl one morning (yes, folks, this is the exciting life of a science writer). Turns out Erin isn’t messing with me. Perhaps I'm one of the last people on Earth to realize toilet water moves with the breeze. Way to go, Soniak.

So, what causes this commotion in the latrine?

In many homes (at least in the U.S.), part of the plumbing system is a pipe that runs up and out to the roof. This outlet, called a “vent stack,” allows sewage gases to vent outside instead of through the toilet, sink or tub—which would make the house reek. The stack also allows air to move through the pipes, which makes wastewater drain smoothly and keeps obnoxious gurgling to a minimum.

When the wind blows over the vent stack outlet on the roof, the air pressure in the pipe is lowered. This is Bernoulli’s principle (“as the speed of a moving fluid increases, the pressure within the fluid decreases”), the same thing that gives airplanes their lift, in action in your bathroom. The lowered pressure in the pipes creates a slight suction effect throughout the plumbing system, pulling on water in the toilet below. As the wind kicks up and dies down, the suction gets stronger and weaker, and the water in the bowl sloshes around accordingly.

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Sylke Rohrlach, Wikimedia Commons // CC BY-SA 2.0
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Animals
These Strange Sea Spiders Breathe Through Their Legs
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Sylke Rohrlach, Wikimedia Commons // CC BY-SA 2.0

We know that humans breathe through their lungs and fish breathe through their gills—but where exactly does that leave sea spiders?

Though they might appear to share much in common with land spiders, sea spiders are not actually arachnids. And, by extension, they don't circulate blood and oxygen the way you'd expect them to, either.

A new study from Current Biology found that these leggy sea dwellers (marine arthropods of the class Pycnogonida) use their external skeleton to take in oxygen. Or, more specifically: They use their legs. The sea spider contracts its legs—which contain its guts—to pump oxygen through its body.

Somehow, these sea spiders hardly take the cake for Strangest Spider Alive (especially because they're not actually spiders); check out, for instance, our round-up of the 10 strangest spiders, and watch the video from National Geographic below:

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iStock
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Food
How to Make Perfect Fried Chicken, According to Chemistry
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iStock

Cooking amazing fried chicken isn’t just art—it’s also chemistry. Learn the science behind the sizzle by watching the American Chemical Society’s latest "Reactions" video below.

Host Kyle Nackers explains the three important chemical processes that occur as your bird browns in the skillet—hydrolysis, oxidation, and polymerization—and he also provides expert-backed cooking hacks to help you whip up the perfect picnic snack.

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