Ask a Scientist: The shower curtain controversy

After completing an intense workout at the gym, I was ready to go back to my room and take a nice, long shower. I hopped in and turned on the water. I breathed in the steam and felt all of my tension melt away. Nothing could ruin this moment.

Then it happened. Out of nowhere, the shower curtain attacked me. I tried to shake it off but every time I thought I was free of its grasp, it came back. The clammy curtain clung to my legs.

While "Attack of the Shower Curtains" is not coming to a theater near you anytime soon, clingy curtains are still annoying. Surprisingly, people have actually spent time and money trying to figure out this mystery.

There appear to be several different theories as to why shower curtains billow annoyingly inward.

Some scientists have argued that it all has to do with buoyancy. When you take a hot shower, the steam heats the air in the shower, causing the warmed air to rise. In order to replace this rising air, cooler air outside the curtain rushes in, bringing the curtain in with it. This is a fairly simple explanation, but has one major flaw: It doesn't explain why a shower curtain is sucked in during a cold shower.

Other scientists believe the shower curtain conundrum can be explained by Bernoulli's principle. According to the theory, as a fluid - such as water or air - moves, the pressure around it drops. So in the case of showers, the water rushing from the shower head creates this low-pressure area.

Because the tendency in nature is for things to move from areas of high pressure to areas of low pressure, air outside moves into the shower. The curtain is simply coming along for the ride.

"The water stream creates an air current and low pressure, drawing the curtain toward it," Peter Olson, professor in the department of Earth and Planetary Sciences, said. "This is an example of the Bernoulli principle in aerodynamics."

The same principle explains how airplanes fly. As the wing moves, air is accelerated over the curved top surface, causing the pressure above the wing to decrease. High pressure air below the wing pushes upward, leading to lift.

Another possible explanation for shower curtain behavior is a lesser known phenomenon called the Coand? effect. It is the tendency of a stream of fluid to be attracted to a nearby surface. In the case of the attacking shower curtain, the roles have been switched: The shower curtain is attracted to the stream of fluid.

The source of this attraction is that air around the stream of water becomes turbulent, creating a low pressure boundary. The air rushing into the shower creates suction, pulling in the shower curtain.

So which one is it? Putting an end to the debate once and for all, David Schmidt, a mechanical engineering professor at the University of Massachusetts, used $28,000 worth of high-powered computer software to model his mother-in-law's bath tub. Two weeks and 1.5 trillion calculations later, Schmidt arrived at an answer. The winner? The Coand? effect.

Because of his work, Schmidt was awarded the Ig Nobel Prize in Physics, which honors unusual and imaginative research, in 2001.Of course, if you don't want to deal with shower curtains, you probably should invest in a shower door or a really heavy shower curtain. Or you could just get rid of it altogether, sacrificing a dry floor and your privacy for a cling-free showering experience.