Knocking on Heaven's Door - Lisa Randall [125]
The reason quantum mechanics comes into play is more subtle. A particle won’t always seem to have exactly its real and true mass. Because the particle can decay, the quantum mechanical uncertainty relation, which says that it takes infinitely long to precisely measure energy, tells us that the energy for any particle that doesn’t live forever can’t be precisely known. The energy can be off by an amount that will be bigger when the decay is faster and the lifetime shorter. This means that in any given measurement, the mass can be close to—but not precisely—the true average value. Only with many measurements can experimenters deduce both the mass—the value that is most probable and to which the average will converge—and the lifetime, since it is the length of time a particle exists before decaying that determines the spread in measured masses. (See Figure 45.) This is true for the W boson, and also for any other decaying particle.
[ FIGURE 45 ] Measurements of decaying particles center around their true masses, but allow for a spread of mass values according to their lifetime. The figure shows this for the W gauge boson.
When experimenters piece together what they measure, using the methods this chapter has described, they might find a Standard Model particle. (See Figure 46 for a summary of Standard Model particles and their properties.)58 But they might also end up identifying something entirely new. The hope is that the LHC will create new exotic particles that will yield insights into the underlying nature of matter—or even space itself. The next part of the book explores some of the more interesting possibilities.
[ FIGURE 46 ] A summary of Standard Model particles, organized according to type and mass. The gray circles (sometimes inside the squares) give particle masses. We see the mysterious variety of the elements of the Standard Model.
Part IV:
MODELING, PREDICTING, AND ANTICIPATING RESULTS
CHAPTER FIFTEEN
TRUTH, BEAUTY, AND OTHER SCIENTIFIC MISCONCEPTIONS
In February 2007, the Nobel Prize—winning theoretical physicist Murray Gell-Mann spoke at the elite TED conference in California, where innovators working in science, technology, literature, entertainment, and other forefront arenas gather once a year to present new developments and insights about a wide variety of subjects. Murray’s crowd-pleasing talk, which was rewarded with a standing ovation, was on the topic of truth and beauty in science. The basic premise of the talk can best be summarized with his words, which echo those of John Keats: “Truth is beauty and beauty is truth.”
Gell-Mann had good reasons to believe his grand statement. He had made some of his most significant Nobel Prize—winning discoveries about quarks by searching for an underlying principle that could elegantly organize the seemingly random set of data that experiments had discovered in the 1960s. In Murray’s experience, the search for beauty—or at least simplicity—had also led to truth.
No one in the audience disputed his claim. After all, most people love the idea that beauty and truth go together and that the search for one will more often than not reveal the other. But I confess that I have always found this assumption a little slippery. Although everyone would love to believe that beauty is at the heart of great scientific theories, and that the truth will always be aesthetically satisfying, beauty is at least in