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Why Does the Shower Curtain Always Try to Get Me?

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For those of you who take baths or are simply unconcerned with hygiene, let me explain the horror that is the “shower curtain effect.” You get in a nice hot shower first thing in the morning. You’re barely awake, but the womb-like confines offer the perfect space to transition from sleepy cretin to functioning human. Until, of course, the shower curtain – who you thought was your friend, who you thought you could trust – gives in to its strange, powerful attraction to running water and billows in towards you. On a good day, it’s a minor annoyance. On a bad day, it’s an unspeakable horror and the curtain actually, like, touches you. And it’s cold. And maybe even a little slimy.

Why does the curtain do this to us? Great minds have been struggling with the problem for years, but until recently all anyone offered were hypotheses. Nobody ever actually tested these explanations and made the results public until a few years ago. That experiment gave us a pretty solid answer, but the theoretical work that came before it is pretty interesting, too. Let’s explore the small handful of different answers that have been suggested over time.

The Bernoulli Principle Hypothesis
We talked about the Bernoulli’s principle the last time I wrote about bathroom science. It states, basically, that an increase in velocity of a fluid (liquid or gas) results in a decrease in pressure around it. With shower curtains, the principle was thought to come into play like this: The water coming out of the shower head causes the air in the shower to start flowing in the same direction that it's traveling, which is parallel to the curtain. The air moving across the inside of the shower curtain causes the air pressure to drop, and the difference in pressure between the two sides of the curtain causes it to move in toward the lower-pressure area. For most of the time that people have been talking about the shower curtain effect scientifically, this has been the leading explanation.

The Buoyancy Hypothesis
Warm air rises up and out of the shower. The air density in the shower is reduced and, like in the Bernoulli hypothesis, the difference in pressure between the shower and outside of the curtain makes the curtain move inward. The big problem with this hypothesis? The curtain still moves in even if you run an ice cold shower.

The Coand? Effect Hypothesis
Jearl Walker, a professor of physics at Cleveland State University who used to write Scientific American’s “Amateur Scientist” column, suggested that the Coand? effect, the tendency of a fluid in motion to adhere to a surface or vice versa, was at work.
* * *
Now, these hypotheses are all well and good. They’re plausible explanations. One was even suggested by a guy who knows a thing or two about physics (and has put his hand in molten lava and poured liquid nitrogen in his mouth to demonstrate its principles). But they don’t mean much without data to back them up.

In 2001, David Schmidt, from the University of Massachusetts, put his own hypothesis to the test and gave us the first evidence-backed explanation to every showerer’s pet peeve.

The Horizontal Vortex Hypothesis
Using a computer model of a shower, Schmidt found that the shower head’s spray creates a horizontal vortex with a low-pressure area center that sucks in the shower curtain. We’ll let Schmidt, who won the 2001 Ig Nobel Prize in Physics for his work, explain his study and its results a little more. As he explained it to Scientific American:

To do the calculation, I drafted a model of a typical shower and divided the shower area into 50,000 minuscule cells. The tub, the showerhead, the curtain rod and the room outside of the shower were all included. I ran [the modeling software] for two weeks on my home computer in the evening and on weekends (when my wife wasn't using the computer). The simulation [which ran some 1.5 trillion calculations] revealed 30 seconds of actual shower time.

When the simulation was complete, it showed that the spray drove a vortex. The center of this vortex, much like the center of a cyclone, is a low-pressure region. This low-pressure region is what pulls the shower curtain in… It is a bit like a sideways dust devil. But unlike a dust devil, this vortex doesn't die out because it is driven continuously by the shower.

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The Delicious Chemistry of Sushi
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iStock

The secret to sushi's delicious taste is invisible to the human eye. Chefs spend years training to properly prepare the Japanese culinary staple, which consists of fresh fish and seasoned rice, either served together or wrapped in seaweed. At its most elemental, as the American Chemistry Society's latest Reactions video explains below, the bite-sized morsels contain an assortment of compounds that, together, combine to form a perfectly balanced mix of savory and sweet. They include mannitol, iodine, and bromophenol, all of which provide a distinctive tang; and glutamate, which adds a savory, rich umami flavor (and turns into MSG when it's combined with a sodium ion).

Take a bite of science, and learn more fun facts about the Japanese culinary staple's long history and unique preparation method by watching the video below.

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Fossilized Poop Shows Some Herbivorous Dinosaurs Loved a Good Crab Dinner
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Lead author Karen Chin of the University of Colorado Boulder
Courtesy the University of Colorado Boulder

Scientists can learn a lot about the prehistoric world through very, very old poop. Just recently, researchers from the University of Colorado-Boulder and Kent State University studying fossilized dinosaur poop discovered that some herbivores weren't as picky about their diets as we thought. Though they mostly ate plants, large dinosaurs living in Utah 75 million years ago also seem to have eaten prehistoric crustaceans, as Nature News reports.

The new study, published in Scientific Reports, finds that large dinosaurs of the Late Cretaceous period seem to have eaten crabs, along with rotting wood, based on the content of their coprolites (the more scientific term for prehistoric No. 2). The fossilized remains of dinos' bathroom activities were found in the Kaiparowits rock formation in Utah's Grand Staircase-Escalante National Monument, a known hotspot for pristine Late Cretaceous fossils.

"The large size and woody contents" of the poop suggest that they were created by dinosaurs that were well-equipped to process fiber in their diets, as the study puts it, leading the researchers to suggest that the poop came from big herbivores like hadrosaurs, whose remains have been found in the area before.

Close up scientific images of evidence of crustaceans in fossilized poop.
Chin et al., Scientific Reports (2017)

While scientists previously thought that plant-eating dinosaurs like hadrosaurs only ate vegetation, these findings suggest otherwise. "The diet represented by the Kaiparowits coprolites would have provided a woody stew of plant, fungal, and invertebrate tissues," the researchers write, including crabs (Yum.) These crustaceans would have provided a big source of calcium for the dinosaurs, and the other invertebrates that no doubt lived in the rotting logs would have provided a good source of protein.

But they probably didn't eat the rotting wood all year, instead munching on dead trees seasonally or during times when other food sources weren’t available. Another hypothesis is that these "ancient fecal producers," as the researchers call them, might have eaten the rotting wood, with its calcium-rich crustaceans and protein-laden invertebrates, during egg production, similar to the feeding patterns of modern birds during breeding season.

Regardless of the reason, these findings could change how we think about what big dinosaurs ate.

[h/t Nature News]

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