For 65 years Uranus was the most distant known planet. During the decades that followed Herschel’s discovery, astronomers found that Uranus was straying from the path predicted by Newton’s laws of motion. A few astronomers suggested that perhaps the gravitational pull of an unknown planet caused Uranus’s surprising behavior. Using the astronomer’s measured positions of Uranus, two young mathematicians—Urbain-Jean-Joseph Le Verrier (1811–1877) in France and John Couch Adams (1819–1892) in England—independently predicted the location of the hypothetical planet. But Adams and Le Verrier could not gain the attention of astronomers in their respective countries, so England and France did not gain credit for a second planetary discovery. Instead, armed with Le Verrier’s predictions, the German astronomer Johann Gottfried Galle (1812–1910) found the planet on his first observing night, just where Le Verrier and Adams had predicted it would be. Galle’s discovery of Neptune in 1846 became a triumph for mathematical prediction based on physical law—and for the subsequent confirmation of theory by observation. Neptune remains the outermost classical planet in the Solar System. (See the Process of Science Figure.)