Back in 1959, I wondered if my uncle’s Nobel Prize was an augur that I was making the right choice. I thought that if he could succeed in the profession, perhaps I would as well. On the other hand, my uncle was also setting the bar incredibly high. My father tried to cheer me up by writing that, prize or no prize, it was better to be a theoretical physicist than an experimental one like my uncle. His reasons for reaching this conclusion were murky at best; he was a professor of ancient history and knew next to nothing about the nitty-gritty of physics. I couldn’t help thinking that his judgment might have more to do with the unfortunately strained relations between the two brothers than with anything else.
In any case, my chosen field–high-energy physics, sometimes called elementary-particle physics–seemed particularly promising, and I was happy with the choice. The interplay between theory and experiment was especially exhilarating. Experimentalists were finding surprising results, with theorists providing explanations shortly afterward; in other cases, theorists made predictions that were quickly proved or disproved by ingenious experiments. The most striking example at the time was Tsung-Dao Lee and Chen Ning Yang’s analysis of how a reaction and its mirror image might be distinguished from one another, a violation of so-called parity symmetry. Their 1956 conjecture was rapidly confirmed, and the Nobel Prize was awarded to them just a year later, in 1957.
In addition, ever-larger accelerators were being put into operation, producing new and often unexpected particles at a prodigious rate. Murray Gell-Mann was pioneering attempts to group these new entities into families, with members related to one another by symmetry considerations. And he was only 30, the same age Lee had been when he received the Nobel Prize. This was a new field with new leaders. I was beginning to think that the situation might be like the earlier development of quantum mechanics, when Wolfgang Pauli, Werner Heisenberg, and Dirac had created a revolution while still in their mid-20s. Since I was only 21, there was hope that I could be a player within a few years if I had the necessary ability.
Fifty years later, I view that moment differently. I see myself not stepping into a rapidly emerging field but entering at the midpoint of a great century-long arc that stretches from Ernest Rutherford’s first scattering experiments to CERN’s Large Hadron Collider–from a seemingly unimportant research exercise carried out by two students to an international endeavor engaging thousands in a decade-long quest to build a multibillion-dollar machine. Though the beginning was simple, the end point is probably the most technologically sophisticated experiment ever attempted.
I called this century-long search an arc, but an ascent might be a more appropriate metaphor, for we have moved steadily over the course of these hundred years toward bigger and bigger experiments. On the other hand, we have also been descending, probing matter at ever smaller scales–from the atom to the nucleus to the protons and neutrons to the quarks and, finally, to whatever comes next. I place my entry into the field not only at a chronological midpoint but also at an organizational one–a time when a single university group could still mount a successful experiment, when computers were in their infancy and analyses could be carried out in days.
Perhaps one should actually start the story 113 years ago, when Henri Becquerel discovered radiation coming from uranium ores; this indicated the presence of a novel energy source, more powerful than anything then known. Two years later, Marie Curie and her husband, Pierre, published their discovery that radioactivity was an atomic property of uranium and other materials. It was not long before Rutherford, a young New Zealander working in Cambridge, England, found that this radiation had two components; he called them alpha rays and beta rays. But I place the beginning of the arc in 1909, when two young physicists working for Rutherford, by then an established professor in Manchester, began at his urging a new kind of experiment. They bombarded a thin gold foil with alpha particles, constituents of alpha rays like the ones Rutherford had discovered a decade earlier. Since that revolutionary experiment, physicists have been smashing ever-more-energetic particles against ever-more-sophisticated targets. The means have changed over the course of the century, but the goal of probing the constituents of matter at smaller scales has not.