You can see it sometimes, if you're out in temperate latitudes on a clear night at dusk or before dawn, when slanting sunlight glints off satellites 300 miles (483 kilometers) high—a dot of light, no brighter than an average star, trudging across the sky in a state of seeming preoccupation like that of the rabbit in Alice's Wonderland, the rippling of Earth's atmosphere (the very distortions that it was designed to rise above) making its smooth, ceaseless fall look halting and perturbed. Which pretty much describes its early career: Repeatedly delayed, then lofted into orbit only to prove myopic, repaired by one space shuttle crew, then improved by others, the Hubble Space Telescope has become the world's most popular scientific instrument, one that has been seen, and seen through, by more people than any before. Scientists feast on its data, while its beautiful images of star clusters, nebulae, and galaxies have made its name—after Edwin Hubble, discoverer of the expansion of the universe—almost as well-known as Google.
It's curiously appropriate that an unmanned telescope should emerge as a symbol of science, since it was instruments generally—and telescopes in particular—that jump-started the scientific revolution. We tend to think of science in terms of great minds conjuring big ideas (an image that Edwin Hubble himself encouraged, at least when it came to his own research), but that paradigm is largely a holdover from prescientific days, when knowledge was sought principally in philosophers' books. In science, instruments can trump arguments. The disinterested verdict of Galileo's telescope did more than Galileo's arguments to lay bare the shortcomings of the regnant Earth-centered model of the cosmos, and Newton's mechanics endured less for their indubitable elegance than for their being able to predict what astronomers would see through their telescopes. Galileo's contemporary Johannes Kepler, whom Immanuel Kant called "the most acute thinker ever born," was quick to grasp that straightforward observations using scientific instruments could sweep away centuries of intelligent but ignorant discourse. Although he was a mathematical theorist who never owned a telescope, Kepler celebrated Galileo's innovation in an ode, addressing the telescope as, "You much knowing tube, more precious than any scepter."