24/06/2020

In Folha, Viana asks: 'What is matter made of?'

Em 1904, Albert Einstein publicou quatro artigos que mudaram a compreensão sobre as leis da física – Science & Society Picture Library/Getty Images

Reproduction of Marcelo Viana's column in Folha de S.Paulo.

A hundred years ago, physics was quite a mess. The explanation of the photoelectric effect, which earned Einstein the 1922 Nobel Prize in Physics, revealed that light behaves very strangely: in some phenomena it seems to be formed by waves, in others it seems to consist of particles. Also, the Bohr-Sommerfeld model described the hydrogen atom very well, but failed embarrassingly to explain the behavior of other atoms.

At least on one thing there was consensus: matter is made of particles (electrons, etc.). Until, in 1924, the young student Louis De Broglie submitted a doctoral thesis to the University of Paris (Sorbonne) with a disturbing suggestion: like light, matter would also have a dual nature, sometimes wave-like, sometimes particle-like.

There was no experimental evidence, and perhaps this speculation would have been ignored were it not for one detail: the shy and reserved De Broglie belonged to one of the great aristocratic families of France, succeeding his father and brother to the title of duke. It was his older brother, Maurice, also a physicist—but who was anything but shy and reserved—who pressured the physics department to take Louis's thesis seriously.

A delicate situation for the department head, Paul Langevin: refusing such an important assignment would be bad for the Sorbonne's reputation if he were honest, but accepting a thesis that would later turn out to be wrong would be equally embarrassing.

Langevin appealed to his friend Einstein, who was visiting, but without giving in. "Of course we know what to do with the thesis," he stated, "but your suggestions are very welcome."

Not knowing what to answer, Einstein sent the paper to his friend Pieter Debye at the University of Zurich, who passed it on to his young Austrian colleague Erwin Schrödinger. “Study this paper and present it at the seminar next month.” Debye said, “It’s a strange wave theory; it doesn’t have equations. See if you can write some equations.”

Initially, Schrödinger wasn't very enthusiastic. But his job at the university was temporary; he had to impress his boss. He retreated to a chalet in the Swiss mountains and returned two weeks later with the information that De Broglie's theory was correct and that he had managed to deduce two equations. He would go on to win the Nobel Prize in Physics in 1933 precisely for formulating these equations.

To read the full text, visit the newspaper's website.