Pierre Curie

French physicist

• Born: May 15, 1859; Paris, France
• Died: April 19, 1906; Paris, France

Nobel Prize–winning French physicist Pierre Curie spent his early career as a crystallographer, during which time he and his brother, Jacques Curie, discovered piezoelectricity. Curie and his wife, Marie Curie, discovered the radioactive elements polonium and radium, thus pioneering the study of radiation.

Primary field: Physics

Specialties: Condensed-matter (solid-state) physics; electromagnetism; nuclear physics

Early Life

Pierre Curie was born on May 15, 1859, in Paris, France. He was the younger of two sons born to Eugène Curie and Sophie-Claire Depouilly Curie. His mother came from a well-to-do family of manufacturers, and his father was a scientist who became a general medical practitioner in order to support his family.

Curie and his brother, Jacques, were especially close, and spent most of their time together. In 1871, Paris refused to accept the French government’s surrender to Germany at the end of the Franco-Prussian War. The workers organized the socialist Paris Commune, which governed from March to May, under siege from the German army. During the siege, Eugène Curie turned his family’s home into a hospital. Twelve-year-old Pierre and fifteen-year-old Jacques went out into the streets to help treat the injured.

Curie was educated at home by his parents and his older brother. In his free time, he hiked through the woods, often bringing home specimens of minerals, flora, and fauna. When Curie was fourteen years old, he worked with a private tutor and discovered an interest in mathematics and physics.

Curie received his bachelor’s degree from the Sorbonne (University of Paris) at the age of sixteen, and his licentiate (master’s degree equivalent) in physics from there when he was eighteen. At the age of nineteen, Curie had to drop out of the university to earn a living. He accepted the position of demonstrator in the Sorbonne physics laboratory, where he worked for the next five years.

Life’s Work

While Curie worked in the physics laboratory at the Sorbonne, his brother Jacques worked as a demonstrator in the university’s mineralogy laboratory. The two brothers began to experiment together. Their work led to the discovery of piezoelectricity, the electric polarization caused by the compression or expansion of crystals in a specific direction. The Curies had foreseen the possibility of this polarization and conducted further experiments to study it. Consequently, they established the conditions necessary to produce the polarization, stated its quantitative laws, and determined the absolute magnitude for certain crystals.

The Curie brothers also learned that when an electric field is applied, the crystals are compressed. Alternating currents can then make the crystals vibrate at ultrahigh frequencies. The brothers invented the piezoelectric quartz balance to measure the amount of electricity involved in this compression. Taking note of the Curies’ work, several other researchers took up the study of piezoelectricity. One of these was German physicist Wilhelm Conrad Röntgen, who would later discover the X-ray.

In 1882, Curie was named laboratory chief at the newly established School of Industrial Physics and Chemistry in Paris. He would remain there, first as laboratory director and then as a professor, for twenty-two years. Jacques left Paris to become a professor of mineralogy at the University of Montpelier. The two often visited each other to help with one another’s experiments.

When Curie was not teaching, he pursued his own studies. In the first two years after accepting the job as laboratory chief, he published two papers on crystallography. Equipment and space were scarce in the new institution and Curie did not have his own laboratory in which to work. Sometimes, he would use students’ laboratories during off-hours, or he would set up his equipment in a hallway.

During the next several years, Curie demonstrated that the magnetism of a substance changes at a certain temperature, now known as the Curie point, also called the Curie temperature. The temperature varies depending on the type of magnetic material. For example, the Curie temperature of iron is 770 degrees Celsius, but for nickel it is 358 degrees Celsius. Curie’s doctoral thesis, submitted to the Faculty of Sciences of the University of Paris in 1895, stated a summary of the relationship between magnetism and temperatures. In paramagnetic substances, the magnetization of the substance is directly proportional to the magnetic field applied in a parallel placement. If the material is heated, the magnetization is reduced and becomes inversely proportional to absolute temperature, which is the thermodynamic relationship between heat and work. This became known as Curie’s law.

Curie met his future wife, the Polish chemist Maria Sklodowska, during the time he was working on his dissertation. They married on July 26, 1895. The couple lived on Curie’s salary alone while Marie continued to study. They would have two daughters together.

For her doctoral dissertation, Marie Curie began experimenting with radium, using Pierre and Jacques Curie’s piezoelectric balance to measure the conductivity of air surrounding substances. French physicist Antoine Henri Becquerel had discovered that uranium compounds emit rays. Marie gave these “Becquerel rays” a new name: radioactivity.

Marie Curie found that pitchblende, an ore of uranium, emitted even higher radioactivity than compounds of uranium and thorium elements. She surmised that pitchblende contained an undiscovered element. Curie abandoned his studies in crystallography to join his wife in extracting the unknown element.

When the Curies discovered one of the two radioactive elements in pitchblende, they named it polonium in honor of Marie’s home country. The Curies published “Sur une substance radioactive contenue dans la pechblende” (On a radioactive substance contained in pitchblende) in July 1898. By December, they had found the second element, which they called radium. They then labored to extract one-tenth of a gram of radium to prove its existence, and in doing so determined that its atomic mass is 226. Since polonium is a result of the disintegration of radium, they were unable to isolate that element.

From 1898 to 1904, the Curies published more than thirty papers on radioactivity. The couple shared the 1903 Nobel Prize in Physics with Becquerel for their research into radiation. The prize money gave the Curies financial security for the first time in their lives. They could have patented their process of extracting radium, but did not because they believed that scientific research belonged to everyone.

More honors followed for the Curies. Pierre Curie was awarded the Davy Medal of the Royal Society of London in 1903, the Matteucci Gold Medal of the National Academy of Sciences in Italy in 1904, and election to the Académie Royale des Sciences (French Academy of Sciences) in 1905.

Curie was run over and killed by a horse-drawn wagon on April 19, 1906, one month before his forty-seventh birthday.

Impact

The Curies’ research into Becquerel’s discovery of radioactivity and their subsequent discoveries of two new radioactive elements helped pioneer the study of radiation. The notion that elements could decay and change into other elements was completely new to the scientific world, and this concept resulted in the growth of the fields of nuclear physics, nuclear chemistry, and radiochemistry. Pierre and Marie Curie knew that radiation could be dangerous, as they both suffered from radiation poisoning, but they also believed that the benefits of radiation would outweigh the harm. As a result of the Curies’ research and later scientists’ research into radioactivity, radiation became useful in a variety of areas, including medicine, manufacturing, and the food industry.

Much of what is remembered about Pierre Curie is tied to his wife’s discoveries in radiation. Nevertheless, Curie made significant contributions to science in his own right. He is remembered in the study of magnetism through the eponymous Curie’s law and Curie’s point, or Curie’s temperature. In addition, Curie’s work in crystallography, particularly his discovery of piezoelectricity, paved the way for a variety of new products. The Curie brothers’ discovery of how to make crystals vibrate at ultrahigh frequencies led to the creation of modern sound equipment. Their piezoelectric quartz balance, later called a piezoelectric electrometer or quartz crystal microbalance, has since been used by scientists as a tool for measuring piezoelectricity. The balance also made possible the creation of radio transmitters and modern quartz timepieces.

Bibliography

Brian, Denis. The Curies: A Biography of the Most Controversial Family in Science. Hoboken, NJ: Wiley, 2005. Print. Focuses on the lives and relationships of the Curie family in addition to their scientific careers, especially their work in radiation. Illustrations, bibliography, index.

Nelson, Wesley G., ed. Piezoelectric Materials: Structure, Properties, and Applications. Hauppauge, NY: Nova Science, 2010. Print. A history of piezoelectricity, covering the properties, characterization, processes, and various applications of piezoelectric materials. Discusses a variety of piezoelectric products, such as sound systems and push-start propane barbecues. Illustrations, index.

Segrè, Emilio. From X-rays to Quarks: Modern Physicist and Their Discoveries. 1980. Mineola, NY: Dover, 2007. Print. Includes a detailed chapter on the discoveries made by Becquerel and the Curies. Illustrations, bibliography, indexes.

Walter, Alan E., and Hélène Langevin-Joliot. Radiation and Modern Life: Fulfilling Marie Curie’s Dream. Amherst, NY: Prometheus, 2004. Print. Covers the science behind radiation and the numerous applications of radiation since its discovery. Illustrations, glossary, index.