It's a serious problem all of us have experienced but few of us ever discuss: poop splash.
This video, by Destin Sandlin of Smarter Every Day, explores the science behind the unfortunate phenomenon that occurs when the poop you drop into the toilet causes water to splash back up and hit you in the butt.
It turns out that the splash is what physicists call a "Worthington jet": a vertical stream of water that shoots upward if an object drops into a pool of water with enough force.
The jet forms because the object opens up a cavity of air in the water as it plunges downward. Water quickly squeezes in to fill the pocket of air, coming from all sides and colliding, forcing it to shoot upward.
Using a high-speed camera and poop-shaped pieces of clay, Sandlin determines that smaller air cavities mean shorter jets of water. He also figures out a neat trick to make sure the jet formed by your poop doesn't shoot up high enough to hit you.
The key is laying a piece of toilet paper over the surface of the water. It'll slow down the falling poop and cause it to pierce the water's surface at more of an angle — and in doing so, eliminate the problem of poop splash forever.