Ethen Godfrey Roberts pulled off a trick called a Superman double backflip the other day and it is a thing to behold:
Sploid says the trick “seems to murder the laws of physics” but if you can close your mouth long enough to stop drooling (this took me several views, BTW), the law of conservation of angular momentum is responsible for the optical illusion that makes the trick look so cool. The trick begins with a tight backwards flip, which happens quickly because all of the weight (human + bike) is distributed close to the center of gravity. By opening his body up in the middle part of the flip, Roberts slows down the rotation, just like a figure skater, diver, or ballerina would by throwing out their arms or legs. And then he gathers himself back onto the bike, which spins quickly again because the weight is all back close to the center. Boom, physics.