Saturday, April 12, 2008 4/11/08-The Starry Messenger

In today's excerpt-Galileo and the telescope. Although the telescope was first invented in 1551 by the Englishman Leonard Digges, it is Galileo's bold work in 1609 that thrusts the instrument and its importance in front of the world. At this time, the financially-strapped Galileo is the chair of mathematics at the University of Padua, and thus under Venice and the Doge, though his heart remains with Tuscany:

"Galileo Galilei was born in Pisa on 15 February 1564--the same year that William Shakespeare was born and the same month that Michelangelo died. ... [Forty-five year old] Galileo first heard rumors of the invention of the telescope (strictly speaking a reinvention, but news of the Digges's telescopes never spread in the sixteenth century) in July 1609, on a visit to Venice. News had been rather slow to travel to Italy on this occasion, since Hans Lippershey, a spectacle maker based in Holland, had come up with the discovery by chance the previous autumn and in the spring of 1609 telescopes with a magnifying power of three times were being sold as toys in Paris. ... Galileo immediately realized that an instrument that could make distant objects visible would be of enormous importance to Venice, where fortunes often depended on being first to identify which ships were approaching the port. He must have imagined that his own boat had at last come in, as he considered how best to turn the news to his advantage.

"But he was almost too late. At the beginning of August, while Galileo was still in Venice, he heard that a Dutchman had arrived in Padua with one of the new instruments. Galileo rushed back to Padua, only to find that he had missed the stranger, who was now in Venice intending to sell the instrument to the Doge. Distraught at the possibility that he might lose the race, Galileo frantically set about building one of his own, knowing nothing more than that the instrument involved two lenses in a tube. One of the most impressive features of Galileo's entire career is that within 24 hours he had built a telescope better than anything else known at the time. Although the Dutch version used two concave lenses, giving an upside-down image, Galileo used one convex lens and one concave lens, giving an upright image. On 4 August, he sent a coded message to [his friend and adviser to the Doge Friar] Sarpi in Venice telling him of his successes; Sarpi, as adviser to the Senate, delayed any decision on what to do with the Dutch visitor, giving Galileo time to build a telescope with a magnifying power of ten times, set in a tooled leather case. He was back in Venice before the end of August, where his demonstration of the telescope to the Senate was a sensation. Being an astute politician, Galileo then presented the telescope to the Doge as a gift. ...

"He then took himself off to Florence to demonstrate another telescope to [Grand Duke] Cosimo II [de' Medici]. By December 1609, he had made a telescope with a magnifying power of twenty times. ... Using his best instrument, Galileo discovered the four brightest (and largest) moons of Jupiter in early 1610. The moons were named the 'Medician stars,' in honor of Cosimo, but are known to astronomers today as the Galilean satellites of Jupiter. With the same instrument, Galileo found that the Milky Way is made up of myriads of individual stars and that the surface of the moon is not a perfectly smooth sphere but is scarred by craters and has mountain ranges. ... All of these discoveries were presented in a little book, The Starry Messenger (Siderius Nuncius), in March 1610. ... The author of The Starry Messenger became famous throughout the educated world (the book was translated into Chinese within five years of its publication)."

John Gribbin, The Scientists, Random House, Copyright 2002 by John and Mary Gribbin, pp. 72, 85-88.

For Martha


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