Cosmos - Carl Sagan [87]
*This exploratory tradition may account for the fact that Holland has, to this day, produced far more than its per capita share of distinguished astronomers, among them Gerard Peter Kuiper, who in the 1940’s and 1950’s was the world’s only full-time planetary astrophysicist. The subject was men considered by most professional astronomers to be at least slightly disreputable, tainted with Lowellian excesses. I am grateful to have been Kuiper’s student.
*Isaac Newton admired Christiaan Huygens and thought him “the most elegant mathematician” of their time, and the truest follower of the mathematical tradition of the ancient Greeks—then, as now, a great compliment. Newton believed, in part because shadows had sharp edges, that light behaved as if it were a stream of tiny particles. He thought that red light was composed of the largest particles and violet the smallest. Huygens argued that instead light behaved as if it were a wave propagating in a vacuum, as an ocean wave does in the sea—which is why we talk about the wavelength and frequency of light. Many properties of light, including diffraction, are naturally explained by the wave theory, and in subsequent years Huygens’ view carried the day. But in 1905, Einstein showed that the particle theory of light could explain the photoelectric effect, the ejection of electrons from a metal upon exposure to a beam of light. Modern quantum mechanics combines both ideas, and it is customary today to think of light as behaving in some circumstances as a beam of particles and in others as a wave. This wave-particle dualism may not correspond readily to our common-sense notions, but it is in excellent accord with what experiments have shown light really does. There is something mysterious and stirring in this marriage of opposites, and it is fitting that Newton and Huygens, bachelors both, were the parents of our modern understanding of the nature of light.
*Galileo discovered the rings, but had no idea what to make of them. Through his early astronomical telescope, they seemed to be two projections symmetrically attached to Saturn, resembling, he said in some bafflement, ears.
*A few others had held similar opinions. In his Harmonice Mundi Kepler remarked “it was Tycho Brahe’s opinion concerning that bare wilderness of globes that it does not exist fruitlessly but is filled with inhabitants.”
*Such tales are an ancient human tradition; many of them have had, from the beginning of exploration, a cosmic motif. For example, the fifteenth-century explorations of Indonesia, Sri Lanka, India, Arabia and Africa by the Ming Dynasty Chinese were described by Fei Hsin, one of the participants, in a picture book prepared for the Emperor, as “The Triumphant Visions of the Starry Raft.” Unfortunately, the pictures—although not the text—have been lost.
*Frequently pronounced “eye-oh” by Americans, because this is the preferred enunciation in the Oxford English Dictionary. But the British have no special wisdom here. The word is of Eastern Mediterranean origin and is pronounced throughout the rest of Europe, correctly, as “ee-oh.”
*Because the speed of light is finite (see Chapter 8).
*The view of Huygens, who discovered Titan in 1655, was: “Now can any one look upon, and compare these Systems [of Jupiter and Saturn] together, without being amazed at the vast Magnitude and noble Attendants of these two Planets, in respect of this little pitiful Earth of ours? Or can they force themselves to think, that the wise Creator has disposed of all his Animals and Plants here, has furnished and adorn’d this Spot only, and has left all those Worlds bare and destitute of Inhabitants, who might adore and worship Him; or that all those prodigious Bodies were made only to twinkle to, and be studied by some few perhaps of us poor Fellows?” Since Saturn