When you drop a piece of buttered bread, it always falls butter-side down.
If a cat is dropped from a high place, it always lands on its feet.
If these two "laws" are true, what do you think would happen if you attached a buttered piece of bread, butter-side up, to a cat's back and then both fell out a window? Would the cat land on its feet? Or will the butter splat on the ground?
In theory, even if you are too lazy (or cautious) to do the experiment yourself you should be able to deduce the obvious result.
The laws of butterology demand that the butter side must hit the ground, and the equally strict laws of feline aerodynamics demand that the cat can land on its feet.
Nature has no way to resolve this paradox.
Therefore, the buttered bread and the flying feline simply do not fall.
That's right, you clever mortal (well, as clever as a mortal can get), you have discovered the secret of antigravity!
To expand on this theory, a buttered cat, when released from above, will drop to a height where the forces of cat-twisting and butter repulsion are in equilibrium. This equilibrium point can be modified by scraping off some of the butter, providing lift... or by clipping some of the cat's hair, allowing descent.
Most of the advanced species of the universe use this principle to drive their space ships within the planetary system. The loud humming heard by most sighters of UFOs is, in fact, the purring of several hundred tabbies. Larger craft use the Maine Coon breed and a lengthwise loaf of sliced sourdough.
The one obvious danger is, of course, if the cats manage to eat the bread off their backs, they will instantly plummet. This, as you all know, happened in Roswell 50 years ago.
Of course the cats will land on their feet, but this usually doesn't do them much good, since right after they make their graceful landing, several tons of red-hot starship and bewildered aliens crash on top of them.
No cats were harmed in the making of this theory