Antoine-Henri Becquerel

Perhaps responsible for more tears of joy than anyone on earth, Antoine Henri Becquerel could be considered the father of the sonogram, that first, pre-natal view of an unborn baby.

The French engineer, physicist, and Nobel laureate discovered evidence of radioactivity, the first step toward what we know today as medical imaging.

Becquerel was a member of one of science’s most distinguished families. From Napoleon the First to World War II, male members of four generations dedicated their lives to research, with each producing important discoveries. Henri’s grandfather, Antoine Cesar Becquerel, invented a method of extracting metals from ores using electrolysis. His father, Alexander Edmond Becquerel, was a physicist who researched solar phenomena and phosphorescence. His son, Jean, became a physicist and studied the optical and magnetic properties of crystals.

Born on December 15, 1852, in Paris, France, Henri grew up loving to play in the garden and his father’s nearby laboratory with his brother, Andre Paul. His father worked as a professor of Applied Physics. Henri’s natural curiosity was fed by a close-up examination of his father’s experiments and his close relationship with his father. From the time he started school at the Lycee Louis-Le-Grand in Paris, Henri was noted as being particularly attracted to science, even trying some of his own investigations as a child.

At 20, Henri was accepted to the Ecole Polytechnique, the country’s top educational institution, to study engineering. There that he met his best friend, Henri Deslandres, who would become a famous astronomer.

Henri Becquerel graduated just two years later, enrolled in graduate studies at the Ecole des Pontes at Claussees, and married Lucie Zoé Marie Jamin. While studying, he began working with his father on a research project which led to the discovery of magneto-optics. He received his degree three years later.

In 1876, Henri gave his first lecture as “répétiteur” at the Ecole Polytechnique. He was already known for the discovery of the magnetic properties of gases and for his work on the rotation of polarized light by a magnetic field. He was said to be frugal in every way, including being quite skilled at conceiving and conducting very small-scale experiments on a tiny budget.

In 1878, his wife died while giving birth to their son, Jean. After her death, he and Jean returned to live with his father.

Like his father, Henri has always been fascinated by and experimented with the phenomenon of phosphorescence.  According to a biography, during the years 1883-84 he pursued his father’s work on the infrared emission spectra of the sun and of hot metallic vapors.

Simultaneously he was analyzing phosphorescence by infrared light. On March 15, 1888, he submitted his thesis “Research on the absorption of light.”

At the age of 36, on March 27, 1889, Henri entered the French Academy of Sciences. He worked tirelessly on multiple experiments and published in 1890 a paper on soil temperatures, work he had started with his grandfather. That year, Henri married his second wife, Louise-Désirée Lorieux. They had no children.

A period of relative quiet in Becquerel’s research career ended in 1895 with the announcement of the discovery of X-ays. The part of the discovery that caught Becquerel’s attention was that X-rays appeared to be associated with a luminescent spot on the side of the cathode-ray tube used in early experiments. Given his extensive background and interest in luminescence, Becquerel wondered whether X-rays might always be associated with luminescence.

He began using naturally fluorescent minerals to study X-rays. He theorized they might be related to fluorescence and phosphorescence, in which substances absorb and emit energy as light.

Becquerel placed a piece of uranium salt on top of a photographic plate wrapped in black paper and enclosed it in a desk drawer. When he developed the plates, he was surprised to find that the plate was exposed in the shape of sharp images of the uranium sample. He then began experiments to show that uranium salts emit penetrating radiation independent of external influences.

Becquerel had demonstrated that radiation could discharge electrified bodies. By discovering radioactivity, he marked the birth of nuclear chemistry.

Working from Henri’s research, by 1880 Pierre Curie and brother Jacques Curie, could demonstrate the piezoelectric effect, the ability of certain materials to generate an electric charge in response to mechanical stress.

In the early 1890s, Henri started teaching full-time. While he was said to prepare carefully, his lectures were reported to be difficult to follow. But despite his poor delivery and obscure reasoning, his research always drew respect from the audience.

The world soon began to understand the power of Henri’s discoveries. According to his biography, in 1900 Becquerel won the Rumford Medal for his discovery of the radioactivity of uranium and he was made an Officer of the French “Legion of Honour.” The Berlin-Brandenburg Academy of Sciences and Humanities awarded him the Helmholtz Medal in 1901. In 1903, Henri shared a Nobel Prize in Physics with Pierre Curie and Marie Curie for the discovery of spontaneous radioactivity. In 1905, he was awarded the Barnard Medal by the U.S. National Academy of Sciences. In 1908, the year of his death at age 55, Becquerel was elected Permanent Secretary of the Académie des Sciences, one of the highest scientific honors the French bestow.  His cause of death was said to be unknown, but it was reported that he had developed serious burns on his skin, likely from the handling of radioactive materials.

Becquerel has also been honored with being the namesake of many different scientific discoveries. The SI unit for radioactivity, the becquerel (Bq,) is named after him. There are craters named for him on the moon and Mars. The uranium-based mineral becquerelite was named after Henri.

The history and evolution of diagnostic imaging are due to the combined efforts of physicists, engineers, computer scientists, doctors, sonographers, physiologists, university researchers, and families like the Becquerels.

Their work underpinned every successive imaging discovery. Combined with research on sound waves, the medical community began to develop new tools for saving lives by looking beneath the skin.

In 1914, Canadian inventor Reginald Aubrey Fessenden designed the first working sonar system in the United States to help detect icebergs.

By 1940, the American acoustical physicist Floyd Firestone made the first ultrasonic echo imaging device to detect internal flaws in metal castings of parts for ships and airplanes.

In 1942, Austrian neurologist Karl Theodore Dussik used ultrasonic beams transmitting through the head to diagnose brain tumors, becoming the pioneer of diagnostic ultrasound.

And by 2019, expectant parents are receiving incredibly detailed, three-dimensional pre-natal images of their bundles of joy. And they cry tears that can be traced all the way back to little Henri Becquerel, playing in his father’s lab.