Knocking on Heaven's Door - Lisa Randall [22]
[ FIGURE 8 ] Our eyes are not always the most reliable means of ascertaining external reality. Here the two checkerboards are the same, but the dots on the one to the right make the squares appear very different.
Although our instinct might be that observations made unaided with our eyes are the most reliable and that we should be suspicious of abstraction, science teaches us to transcend this all too human inclination. The measurements we make with the instruments we design are more trustworthy than our naked eyes, and can be improved and verified through repetition.
In 1611, the church accepted the radical proposition that indirect measurements are valid. As Tom Levenson relates in his book Measure for Measure,7 the scientific establishment of the church had to decide whether observations from a telescope were trustworthy. Cardinal Robert Bellarmine pressed the church scholars to decide this issue, and on March 24, 1611, the four leading church mathematicians concluded that Galileo’s discoveries were all valid: the telescope had indeed produced accurate and reliable observations.
Another commemorative brass medallion that the Paduans shared with me beautifully summed up the pivotal nature of Galileo’s achievement. On one side is a picture of the 1609 presentation of the telescope to the Signoria of the Republic of Venice and to the Doge, Leonardo Dona. The other side has an inscription noting that the act “marks the true birth of the modern astronomical telescope” and begins the “revolution in man’s perception of the world beyond planet Earth,” “a historic moment that crosses the boundaries of Astronomy, making [it] one of the starting points of modern Science.”
Galileo’s observational advantages led to an explosion of further discoveries. Repeatedly, as he stared up into the cosmos, he found new objects that were beyond the range of the naked eye. He found stars in the Pleiades and throughout the sky that no one had seen before, sprinkled among the brighter ones that were already known. He publicized his discoveries in his famous 1610 book, Sidereus Nuncius (Starry Messenger), that he raced to complete in about six weeks. He hastily performed his research while the printer worked on the manuscript, eager to impress and gain the support of Cosimo II de’ Medici, the Grand Duke of Tuscany—and a member of one of Italy’s richest families—before someone else with a telescope might manage to publish first.
Because of Galileo’s insightful observations, an explosion of understanding occurred. He asked a different type of question: how rather than why. The detailed discoveries that were possible only with his telescope naturally led him to the conclusions that were to anger the Vatican. Specific observations convinced Galileo that Copernicus had been correct. For him, the only worldview that could consistently explain all of his observations relied on a cosmology in which the Sun, and not the Earth, was the center of the galaxy around which all planets orbited.
The moons of Jupiter were among the most critical of these observations. Galileo could see the moons as they appeared and disappeared and moved in accordance with their orbit around the giant planet. Before this discovery, a stationary Earth seemed the obvious and only way to explain the Moon’s fixed orbit. The discovery of Jupiter’s moons meant that it too had satellites in tow despite its motion. This lent credence to the possibility that the Earth could also be moving and even orbiting about a separate central body—a phenomenon that was explained only later when Newton developed his theory of gravity and its prediction of the mutual attraction of celestial objects.
Galileo named Jupiter’s moons Medicean stars, in honor of Cosimo II de’ Medici—further demonstrating his understanding of funding—another key aspect of modern science. The Medicis indeed decided to support Galileo’s research. Later on however, after Galileo had been granted funding for life from the city of Florence, the moons