these are responses to a contest sponsored by omni magazine:

grand prize winner:

when a cat is dropped, it always lands on its feet, and when toast is dropped, it always lands with the buttered side facing down. i propose to strap buttered toast to the back of a cat; the two will hover, spinning inches above the ground. with a giant buttered cat array, a high-speed monorail could easily link new york with chicago.

runners-up:

birds take off at sunrise. on the opposite side of the world, they are landing at sunset. this causes the earth to spin on its axis.

the reason hot-rod owners raise the backs of their cars is that it's easier to go faster when you're always going downhill.