Anyone that takes martial arts learns how to fall... it has nothing whatsoever to do with defying physics and everything to do with knowing how your body is moving and how it will impact. While you cannot change direction while in the air, you CAN alter your body position and how you land.

The worst I've ever been injured in a bike crash was riding down a dark street at night with no lights... I couldn't see where the ground was to land properly... every other time I've been able to roll with the fall and not suffered serious injuries (Including getting hit nearly head on by a truck)