When trying to explain what motivates me as a physicist, the film A Passage to India (1984) comes to mind. Based on the play by Santha Rama Rau, adapted from the novel by E M Forster, it describes the fallout from a rape case in the fictional city of Chandrapore, during the British Raj in India in the 1920s. What keeps the viewer’s attention is the subtlety of the relationships between the characters – particularly the fragile friendship between the man accused of the rape, Dr Aziz, and an Englishman, Mr Fielding. Data about identity alone, such as race, class, gender or educational status, can never reveal these dynamics nor capture why they fascinate us. When the case arrives in court, ostensibly similar people behave very differently in relation to the defendant. The dynamics of individual behaviour trump any immutable labels we might apply; yet these static labels also impose constraints on just how far any individual can go. We watch, we theorise, and we update our knowledge of the characters and the forces at work. By the end, we find that Fielding and Aziz are more alike than we’d thought, having created a new bond on the basis of a more complete understanding of one another.
The curiosity that drives many particle physicists isn’t so different from what keeps us watching A Passage to India. The obvious and immutable data about the identity of elementary particles include their spins, their electric charges and their masses. From muons to charms, we can learn such information pretty quickly. But it takes years, even lifetimes, to reveal both the nature and degree of their relationships. The neutrino, for example, was introduced in 1930 by Wolfgang Pauli, who needed to account for the fact that energy was conserved when a nucleus broke apart. But he would never have guessed how deep the relationship is between a left-handed spinning electron and the neutrino. It took more than 40 years of careful observations and ingenious theoretical work to reveal the deeper unified relationship they have together: via the fundamental force we now know as the ‘weak force’. That’s where the deepest and most satisfying learning in particle physics is to be found: through painstaking observations and the sifting of evidence comes a creative willingness to allow for multiple possibilities. [Continue reading…]