And there is no indication that the reason why decaying dams are found at each point where the town brook falls ten feet is because there used to be a dozen factories on its banks using the gravity power of falling water to turn out a variety of industrial products.

FORBES: A Cautionary Tale From America's Hometown

And dark energy may turn out to be almost the mirror opposite of gravity - a repulsive rather than an attractive force, and one that strengthens with distance rather than weakening.

BBC: Getting the measure of dark energy

An anomaly in the orbit of Mercury provided one of the first clues that the laws of gravity as described by Newton were incomplete, which, in turn, led Einstein to general relativity.

ECONOMIST: A space oddity