Why Does My Shower Curtain Liner Attack Me?

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iStock

For most of us, showers are a time to block out external stimuli and enjoy a moment to ourselves. The blissful monotony can often lead to creative inspiration or new ideas. Celebrated screenwriter Aaron Sorkin once said he takes up to six showers a day to help unblock his mind and resolve story problems.

But not all showers can make us part of the wealthy Hollywood elite. Some showers can become exercises in dread and frustration. We’re referring to the persistent attack of the shower curtain liner.

Liners have a tendency to billow inward during showers, enveloping themselves around our calves and forcing us to swat them away. As problems, go, it’s fairly innocuous. But that doesn’t mean science hasn’t tried to understand the physics behind the phenomenon.

Back in 1938, Popular Science theorized that liners were behaving badly as a result of air currents. When hot air from the warm water rises, cold air around the tub seeks to replace it, causing the liner—which is in between—to grow agitated. This explanation seemed to satisfy people for a while, until someone pointed out that the liners tend to move even during a cold shower.

Others believed the liner was acting as a result of Bernoulli's principle, which states that air pressure around fluid decreases when the fluid is moving quickly. With a difference in air pressure inside and outside the tub, the liner will move.

In 2001, someone finally had the means and motivation to examine this theory more closely. David Schmidt, an assistant professor at the University of Massachusetts Amherst, used computer software developed to examine fluid spray to assist in diesel and aircraft engines to put Bernoulli's theory to the test. This being 2001, it took his home PC two weeks to run the simulation, which Schmidt programmed to replicate a typical shower (rod, curtain, liner, shower head).

Schmidt found that the shower spray created a vortex with a low-pressure region—a little like the center of a cyclone. That region is what “sucks” the liner inward. Despite the relative calm of a shower, the simulation indicated that you’re basically in the eye of a very low-level storm.

For more answers, Schmidt would probably have to consider overseeing a real-world model, but he said he doesn’t have the time or inclination to take the whole shower cyclone science thing to the next level.

That’s not quite the end of the story, though. In 2007, physics author Peter Eastwell tinkered with a shower set-up and noted that the cyclone effect was more pronounced in hotter than cooler water, and that factors like the distance of the liner from the spray affected the liner’s movement.

Clearly, more work needs to be done on this important issue. Until then, using a heavier liner or attaching weights to the bottom can prevent billowing. Alternately, you could just install a shower door. Aaron Sorkin probably has one.

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Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

Are Any of the Scientific Instruments Left on the Moon By the Apollo Astronauts Still Functional?

Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Heritage Space/Heritage Images/Getty Images

C Stuart Hardwick:

The retroreflectors left as part of the Apollo Lunar Ranging Experiment are still fully functional, though their reflective efficiency has diminished over the years.

This deterioration is actually now delivering valuable data. The deterioration has multiple causes including micrometeorite impacts and dust deposition on the reflector surface, and chemical degradation of the mirror surface on the underside—among other things.

As technology has advanced, ground station sensitivity has been repeatedly upgraded faster than the reflectors have deteriorated. As a result, measurements have gotten better, not worse, and measurements of the degradation itself have, among other things, lent support to the idea that static electric charge gives the moon an ephemeral periodic near-surface pseudo-atmosphere of electrically levitating dust.

No other Apollo experiments on the moon remain functional. All the missions except the first included experiment packages powered by radiothermoelectric generators (RTGs), which operated until they were ordered to shut down on September 30, 1977. This was done to save money, but also because by then the RTGs could no longer power the transmitters or any instruments, and the control room used to maintain contact was needed for other purposes.

Because of fears that some problem might force Apollo 11 to abort back to orbit soon after landing, Apollo 11 deployed a simplified experiment package including a solar-powered seismometer which failed after 21 days.

This post originally appeared on Quora. Click here to view.

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