All the sounds of the earth are like music. Oscar Hammerstein II Sometime around the year 1600, the German astronomer and mathematician Johannes Kepler undertook a study of the motions of the planets. Over the next decade-and-a-half he revolutionized the way astronomers understood the heavens. While every right-thinking star-gazer believed that the planets moved in circles around the Sun, Kepler proved that they travelled in ellipses—slightly squashed circles. Then, in 1618,

Horses evolved in North America during the Pliocene Epoch, some 4 to 4.5 million years ago. Superbly adaptable, this subspecies of the genus Equus had, within 2 million years, spread to South America and, by way of the Bering land bridge, to Asia and beyond. In the Americas, the horse flourished until 12,000 to 10,000 years ago, when, for reasons that are not clear, the species disappeared. Disease, climate change, and the arrival of meat-eating humans likely played a part. B