Knocking on Heaven's Door by Lisa Randall Read Free Book Online Page B

validity.
    Every area of physics reveals this effective theory idea at work. Science evolves as old ideas get incorporated into more fundamental theories. The old ideas still apply and can have practical applications. But they aren’t the domain of frontier research. Though the end of this chapter has focused on the particular example of the physical interpretation of light through the ages, all of physics has developed in this manner. Science proceeds with uncertainty at the edges, but it is advancing methodically overall. Effective theories at a given scale legitimately ignore effects that we can prove won’t make a difference for any particular measurement. The wisdom and methods we acquired in the past survive. But theories evolve as we better understand a larger range of distances and energies. Advances give us new insights into what fundamentally accounts for the phenomena we see.
    Understanding this progression helps us better interpret the nature of science and appreciate some of the major questions that physicists (and others) are asking today. In the following chapter, we’ll see that in many respects, today’s methodology began in the seventeenth century.

CHAPTER TWO
    UNLOCKING SECRETS
    The methods scientists use today are the latest incarnation of a long history of measurements and observations that have been developed over time to verify and—as importantly—rule out scientific ideas. This need to go beyond our intuitive apprehension of the world to advance our understanding is reflected in our very language. The root used in Romance languages for the verb “to think”— pensum —comes from the Latin verb “to weigh.” English speakers, too, “weigh” ideas.
    Many of the formative insights that ushered science into its modern expression were developed in Italy in the seventeenth century, and Galileo was a key player. He was among the first to fully appreciate and advance indirect measurements —measurements made with an intermediate device—as well as to design and use experiments as a means of establishing scientific truth. Moreover, he conceived abstract thought experiments that helped him create and consistently formulate his ideas.
    I learned about Galileo’s many insights that fundamentally changed science when I visited Padua in the spring of 2009. One impetus for my visit was a physics conference that the Paduan physics professor Fabio Zwirner had organized. The other was to receive an honorary citizenship of the city. I was delighted to join my fellow physicist attendees as well as the esteemed group of fellow “citizens,” including the physicists Steven Weinberg, Stephen Hawking, and Ed Witten. And—as a bonus—I had a chance to learn some science history.

    My trip was auspiciously timed, as 2009 was the 400th anniversary of Galileo’s first celestial observations. The citizens of Padua were particularly attentive, since Galileo had been lecturing at the university there at the time of his most significant research. To commemorate his famous observations, the town of Padua (as well as Pisa, Florence, and Venice—other towns that figured prominently in the scientific life of Galileo) had arranged exhibits and ceremonies in his honor. The physics talks took place in a hall in the Centro Culturale Altinate (or San Gaetano), the same building that housed a fascinating exhibit that celebrated Galileo’s many concrete accomplishments and highlighted his role in changing and defining what science means today.
    Most people I met appreciated Galileo’s achievements and conveyed their enthusiasm for modern scientific developments. The interest and knowledge of the Paduan mayor, Flavio Zanonato, impressed even the local physicists. The head of the city not only actively engaged in scientific conversation at a dinner following the public lecture I gave, but during the lecture itself he surprised the audience with an astute question about charge flow at the LHC.
    As part of the citizenship