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wrong—conclusion about the nature of the solar system. He supported an odd hybrid of the Ptolemaic system, with the Earth at the center, and the Copernican system, where planets orbited the Sun. (See Figure 10 for a comparison.) The Tychonic universe agreed with observations, but it wasn’t the most elegant interpretation. It was, however, more satisfactory to the Jesuits than Galileo’s view, since according to Tycho’s premises—as with the Ptolemaic theory that Galileo’s observations contradicted—the Earth didn’t move. 8

    [ FIGURE 10 ] Three proposals to describe the cosmos: Ptolemy postulated that the Sun, along with the Moon and other planets, circled the Earth. Copernicus (correctly) suggested that all the planets orbit the Sun. Tycho Brahe postulated that nonterrestrial planets orbited the Sun, which in turn orbited the Earth at the center.
    Galileo rightly recognized the jury-rigged nature of the Tychonic interpretation and came to the correct and most economical conclusion. Newton’s rival Robert Hooke later noted that both the Copernican and Tychonic theories agreed with Galileo’s data, but one was more elegant, saying “but from the proportion and harmony of the World, [one] cannot help but embrace the Copernican Arguments.” 9 Galileo’s instincts about the truth of the more beautiful theory turned out to be correct, and his interpretation ultimately prevailed when Newton’s theory of gravity explained the consistency of the Copernican setup and predicted planetary orbits. Tycho Brahe’s theory, as was true for Ptolemy’s, was a dead end. It was wrong. It wasn’t absorbed in later theories because it couldn’t be. Unlike the situation with an effective theory, no approximation of the true theory leads to these non-Copernican interpretations.

    As the failure of the original Tychonic theory showed, and as Newtonian physics verified, the subjective criterion of the more economical explanation can also play an important role in the initial scientific interpretation. Research involves the search for underlying laws and principles that will encompass the structures and interactions being observed. Once a sufficient number of observations exist, a theory that economically incorporates the results while providing a predictive underlying framework ultimately wins out. At any point in time, logic takes you only so far—something particle physicists are painfully aware of as we await the data that will ultimately determine what we believe about the underlying nature of the universe.
    Galileo helped lay the groundwork for how all scientists work today. Understanding the progression that he and others initiated helps us to better understand the nature of science—in particular, how indirect observations and experiments help us ascertain the correct physical description—as well as some of the major questions that physicists ask today. Modern science builds on all his insights—the usefulness of technology, experiment, theory, and mathematical formulation—in its attempts to match observations to theory. Critically, Galileo recognized the interplay of all these elements in formulating physical descriptions of the world.
    Today we can be more free in our thinking, allowing the Copernican revolution to continue as we explore the outer reaches of the cosmos, and theorize about possible extra dimensions or alternative universes. New ideas continue to make human beings less and less central, both literally and figuratively. And observations and experiments will either confirm or reject our proposals.
    The indirect methods of observation that Galileo employed currently find dramatic expression in the Large Hadron Collider’s elaborate detectors. A final display in the Paduan exhibit showed the evolution of science up to modern times, and even presented pieces of LHC experiments. Our guide confessed he had been confused by this until he recognized that the LHC is the ultimate microscope to date, probing