So, what would happen if we stick a slice of toast with butter to a cat's back and we throw it to the air? The cat, by law, will land on its feet, but the toast, (by law too) will land on the butter's side. Against this problem of physics laws, the nature chooses the best (and laziest, I think) way of taking a solution: the cat may just not fall. In fact, most civilized species in the universe already use this principle in order to build their UFO's. Thus, the buzzing that you can hear when you see an UFO is actually the purr from the cats.