A remarkable team: Marie Curie and her daughter Irène worked together as nurses during World War I. Later they would work together as physicists.
It was in 1911 that Rutherford realized what the Manchester experiments implied: the atom, contrary to prevailing beliefs, was composed of electrons moving about a minuscule, massive core. The following year he used the term nucleus to describe that core. Measuring typically little more than a hundred-thousandth of the atom’s radius, the nucleus nevertheless contained essentially all of its mass.
Twenty years later, probing deeper, physicists discovered that the nucleus is composed of neutrons and protons, presumably held together by a previously unimagined force. Forty years after that, they found that neutrons and protons are in turn each made up of three quarks. This year, when the Large Hadron Collider begins operation in full, we will take the next step on the journey–one whose progression Abraham Pais, a physicist and historian, has described in a book aptly called Inward Bound.
Physics’ First Families
Over the span of this century-long arc, the energy of the projectiles employed has increased by a factor of a million, the cost of the necessary apparatus from a few hundred to billions of dollars, and the size of the teams at work on a typical experiment from at most two or three to hundreds. But this story is much more than simply one of bigger machines and larger expenditures. It is also a tale of the people who achieved this extraordinary growth–people who were linked to one another, sometimes by blood or marriage (as I can attest, having a slew of relatives in what I sometimes jokingly refer to as “the family business”), but in all cases by common aims.
I had a romanticized image of the field when I entered it 50 years ago, but it’s been moderated by finding out about some of the bitter disputes that have arisen along the way. (Two of my early heroes, Lee and Yang, once as close as brothers, have not spoken to each other for decades.) Yet while I now see the warts, I also have a greater appreciation for the support and even affection so common in the physics community. Great labs such as the Cavendish at Cambridge, Curie’s Radium Institute, and Niels Bohr’s Institute for Theoretical Physics often fostered quasi-familial feelings, occasionally heightened by the sight of parent and child working side by side.
A family-like atmosphere certainly existed wherever Rutherford presided. At the end of World War I, he left Manchester. Joseph John Thomson, who had received a Nobel Prize in 1906 for discovering the electron, decided to step down from Cambridge’s Cavendish Professorship, a post he had held for 35 years. Rutherford, then at the peak of his powers, was his natural replacement. He accepted, and for the next 15 years the Cavendish Lab, under his leadership, was the world’s premier research facility in nuclear physics.
At the Cavendish, Rutherford was jovial but stern when he needed to be, always encouraging the group he called “his boys.” Bohr once wrote of him, “However modest the result might be, an approving word from him was the greatest encouragement for which any of us could wish.” There was no doubt who was the “father” and who had the last word, but Rutherford’s intuition was formidable and his judgment excellent, and he was never threatened by suggestions from others. He began his day by going over the physics news with the assistant head of the lab, James Chadwick, who had worked by Rutherford’s side since his own undergraduate years at Manchester before World War I. Rutherford would then walk around the lab, offering suggestions. When preliminary results were available, he would sit on a stool near the experimenter’s lab bench, pull a pencil out of his waistcoat, and check to see if the data seemed right. The lab’s restrictions now seem archaic: doors that shut punctually at 6:00 p.m., mandatory vacations, and a prevailing ethos that you built your own equipment–not too expensively, either. Viewed through today’s lenses, Rutherford’s behavior was paternalistic. But there was no resentment.
No experiment at the Cavendish would be more influential than Chadwick’s 1932 discovery of the neutron. Ushering in the modern era of nuclear physics, it was a triumph for Rutherford’s boys, and it marked the start of a period in which experimentalists regained the lead from theorists like Bohr, Heisenberg, and Schrödinger, who had been dominant since Rutherford discovered the nucleus 20 years earlier.