In 2016, a senior talent show launched a new viral craze: water bottle flipping. As improbable as it seems at first glance, physics is actually on your side when it comes to pulling this trick off. As explained in this classroom-oriented paper and the video abstract below, the sloshing of the water in the bottle as it flips slows its rate of rotation, which creates the stable landing. You don’t even need water to make the trick possible. Using two tennis balls will also give a stable flip – provided they have room to spread out. When they fly apart, they change the bottle’s moment of inertia and that slows down the rotation rate. All in all, it’s a great lesson in conservation of angular momentum.