Pierre Curie

Pierre Curie was born in Paris in 1859 to a family of physicians who educated him at home rather than entrust him to the lycée system. He received his licence in physics from the Sorbonne at sixteen and a Master's two years later, but the family had no money for further study and he took a junior post as laboratory assistant. Working alongside his older brother Jacques in 1880, he made his first major discovery: certain crystals — quartz, tourmaline, Rochelle salt — produce a measurable voltage when squeezed along specific axes. The brothers called the effect piezoelectricity ("pressure electricity"), and within a year had built the first piezoelectric quartz electrometer, an instrument so sensitive it would later let physicists weigh radioactive samples in micrograms.

His doctoral thesis, defended in 1895, settled a question that had nagged at magnetism for half a century: why does iron lose its magnetic memory when heated? Curie measured the magnetic susceptibility of dozens of materials over wide temperature ranges and showed that every ferromagnet has a sharp critical temperature — now called the Curie temperature — above which the spontaneous magnetisation collapses to zero. The same thesis established the inverse-temperature scaling of paramagnetic susceptibility, Curie's law, which Pierre Weiss later refined into the Curie–Weiss law. These two results were the foundation on which the twentieth-century theory of magnetism would be built.

In the same year he married Marie Skłodowska, a Polish physicist who had come to Paris to study because Polish universities did not admit women. Together they identified two new radioactive elements in pitchblende — polonium (named for her homeland) in July 1898 and radium that December — and shared the 1903 Nobel Prize in Physics with Henri Becquerel. Pierre had finally been promoted to a full professorship at the Sorbonne in 1904. Two years later, walking across the rue Dauphine in heavy rain on 19 April 1906, he slipped under a horse-drawn cart and was killed instantly when the rear wheel crushed his skull. He was forty-six. Marie inherited his chair, becoming the first woman to teach at the Sorbonne, and continued his lectures the week after the funeral. Pierre left behind a remarkable double legacy: piezoelectric crystals now run every quartz watch and ultrasound scanner on the planet, and the Curie temperature still anchors every solid-state textbook on magnetic phase transitions.