Gazing Deeper Still: Four Hundred Years Ago, Galileo and His Telescope Brought the Heavens into Focus, Setting the Stage for Modern Astronomy
Sobel, Dava, Science News
Such a small thing, really--two pieces of glass and a tube no longer than the span of a man's arm. The first telescope that Galileo built (and I don't mean he was the first to build one, for surely he wasn't) played tricks with distance and size. The device transported faraway objects into the viewer's presence, and magnified them there. As Galileo demonstrated to the Doge of Venice in 1609, even an entity invisible to the naked eye, such as an enemy ship on the horizon, would loom large within the purview of his spyglass.
Later, alone in the dark, after he'd learned how to grind better lenses, Galileo pointed his instruments skyward to reveal uncomfortable truths about the universe:
1. The supposedly smooth, silvery orb of the moon mimicked the Earth with chains of mountains and depths of valleys. 2. The familiar constellations contained more stars than anyone had counted, while the mysterious Milky Way consisted of nothing but stars, too densely packed for unaided eyes to discern. 3. The planet Jupiter commanded a retinue of four attendant bodies--"never seen since the beginning of time," as Galileo pointed out--whose positions changed from hour to hour. 4. Venus, when followed through the telescope, waxed and waned like the moon. 5. And the large pair of companions on either side of Saturn occasionally disappeared!
This year, four centuries after those early nights of wonder, the International Year of Astronomy salutes Galileo for ushering in a new worldview. 2009 also commemorates the 400th anniversary of the publication of Astronomia Nova, by Johannes Kepler, who propounded laws of planetary motion as stunning as Galileo's observations.
Today giant telescopes dominate mountaintops around the world, fly through space, even orbit other planets. Yet it is still possible to feel awe looking through a simple tube at the things Galileo saw. Perhaps 10 million children and adults will get that chance for themselves as they look up through IYA "Galileoscopes" and other inexpensive telescopes distributed through schools and science centers in scores of countries this year. Given the number of astronomers who recall their first glimpse of Saturn's rings as a transformative moment, I'm betting the IYA may produce a large crop of lifelong stargazers.
Unfortunately, one of the sights that most delighted Galileo--the live view of the Milky Way--is already all but lost for most people, drowned out by the glare of urban skyglow. Understandably, therefore, an important focus of IYA activities is raising "dark skies awareness" among the 3-billion--plus city dwellers of planet Earth.
As one might expect in a multicentennial celebration year, Galileo himself is not only lionized, but also under attack as undeserving of all the attention directed at him. In England, for example, Thomas Harriot boosters are claiming that their countryman sketched the moon through a rudimentary telescope several months before Galileo did. This is true, and I hope more people will come to know and admire Harriot--not to mention the innovative Islamic astronomers of the Middle Ages and many other unsung heroes--as part of the IYA spin-off. Still, Harriot's drawings of the moon are dimensionless renderings, whereas Galileo's explore the play of light on a textured surface. By combining his artistic training in perspective with his mathematical skills, Galileo gauged the heights of the lunar mountains from his backyard in Padua.
Galileo's explanations of his astounding discoveries won him admiring followers and princely rewards, but also attracted jealous enemies and zealous defenders of the faith. Even now, religious and philosophical questions that he raised reverberate--and make him the one astronomer that so many people recognize, remember something about, react to on an emotional level.
Galileo never set out to be an astronomer. Had the telescope not distracted him from his other scientific pursuits, we would remember him today "only" as the father of experimental physics. …