In the spring of 1905, a tempestuous Italian medium named Eusapia Palladino arrived in Paris, ready to prove that she was able to summon the spirits of the dead.

She conducted more than 40 séances for a team of investigators, producing a range of dramatic and confounding phenomena. Huddled around a table, participants watched as objects floated through the room and luminous forms shimmered in the air. They felt the touch of invisible hands. The table where they sat levitated above the ground.

Among the spectators who flocked to see the famed Palladino were two of history’s most esteemed scientific minds: Marie and Pierre Curie. In 1903, just two years before they took part in the séances, the Curies had been awarded the Nobel Prize for Physics in recognition of their groundbreaking work on radioactivity. Marie had been the first woman in France to earn a doctorate. Pierre was a professor at the prestigious Sorbonne University. And yet, in spite of their towering reputations as evidence-based researchers, the Curies approached Palladino’s séances with open minds. At least one of them came to believe that the medium truly did possess supernatural powers.

Today, it seems strange, even unthinkable, that a pair of respected scientists would give serious consideration to a woman who claimed to communicate with the dead. But the Curies were far from alone.

"Physical Phenomena”

Eusapia Palladino demonstrates her ability to levitate a table during a séance in 1898 at the home of astronomer Camille Flammarion.H. Mairet, Wikimedia Commons // Public Domain

Palladino had been invited to Paris by members of the Institut Général Psychologique (IGP), which was devoted in part to the rigorous study of supernatural phenomena. The research was carried out by a team of respected academics, whose séances with Palladino were considered to be the IGP’s “most ambitious project,” writes historian Sofie Lachapelle. During each session, investigators measured Palladino’s temperature, blood pressure, and reflexes. They recorded meteorological conditions, acoustic vibrations, and magnetic fields. The goal, according to Lachapelle, was to determine whether Palladino’s phenomena were authentic and to place them within the context of known natural laws.

The IGP researchers weren't the first to attempt an empirical study of Palladino, who had captured the attention of intellectuals across Europe and beyond. She was charismatic, but volatile, oscillating suddenly between tears and laughter, flying into rages when offended and jumping flirtatiously into the laps of shocked investigators. She was also a known cheat, having been caught using her hand, leg, and even a strand of hair to create the illusion that objects were moving spontaneously during séances. But Palladino nevertheless produced chilling spectacles that even skeptical scientists struggled to explain. And so they continued to try and figure her out.

“No other medium, producing ‘physical phenomena,’ has been studied with so much care, for so long a period, and by so many scientific men,” wrote Hereward Carrington, a science journalist who investigated Palladino, in 1909.

The powerful force behind scientists’ interest in Palladino—and in the supernatural, more generally—was spiritualism, a religious and cultural movement rooted in the belief that the souls of the dead can communicate with the living, usually through a medium. Spiritualism was born in New York state in the mid-19th century and quickly swept through America and Europe. Though not without controversy—many people firmly believed that spiritualist mediums were frauds—the movement appealed to some of the most enlightened thinkers of the day. Among its famous adherents were Sir Arthur Conan Doyle, a physician by training and creator of the hyper-rational detective Sherlock Holmes; the celebrated physicist Sir Oliver Lodge, whose experiments with electromagnetic waves paved the way for wireless telegraphy; and Alfred Russel Wallace, a pioneer in the study of evolution.

Spiritualists didn't see their religion as being antithetical to science. They believed mediums offered proof of an unseen spirit realm—a realm that was no more implausible than the spate of intangible physical forces that came to light at the turn of the 20th century. “This was a time when many scientists had begun to explore an invisible world,” Barbara Goldsmith writes in Obsessive Genius: The Inner World of Marie Curie. Landmark research was providing unprecedented insight into radio waves, magnetism, X-rays, and radioactivity—a phenomenon that the Curies had helped uncover with their discovery of the elements polonium and radium. “In a world where messages were being transmitted invisibly by means of the telegraph,” Goldsmith writes, “spiritualists came to believe that, if this was possible, why not a Spiritual Telegraph with which one might communicate with the dead?”

The Curies Investigate

Marie and Pierre Curie are pictured in their laboratory in 1898.Culture Club/Getty Images

Marie and Pierre Curie readily admitted that nature was rife with mysteries that scientists had yet to identify and study. “[W]e know little about the medium that surrounds us, since our knowledge is limited to phenomena which can affect our senses, directly or indirectly,” they wrote in 1902, acknowledging that they did not fully understand the origin of radioactive energy.

Pierre was particularly fascinated by the paranormal. Introduced to spiritualism by his brother, the scientist Jacques Curie, he confessed in an 1894 letter to Marie that “those spiritual phenomena intensely interest me.” He believed that the paranormal realm was relevant to “questions that deal with physics,” and according to biographer Anna Hurwic, thought that spiritualism might uncover “the source of an unknown energy that would reveal the secret of radioactivity.”

Both Curies attended multiple séances with Palladino, which they viewed as scientific experiments. Pierre was vocal about his conviction that at least some of the medium’s phenomena were genuine. “It was very interesting,” he wrote to his physicist friend Georges Gouy in 1905, “and really the phenomena that we saw appeared inexplicable as trickery.”

The sessions had taken place “in a locale prepared by us with a small number of spectators all known to us and without a possible accomplice,” Curie explained. The lighting in the room was “sufficient” to ensure that Palladino could not easily cheat, and participants had been holding her hands and feet so she could not try any of her known tricks. And yet, somehow, she had produced a spooky string of effects: “tables raised from all four legs, movement of objects from a distance, hands that pinch or caress you, luminous apparitions.”

Just a few days before his death in 1906, Pierre wrote again to Gouy describing the last Palladino séances he would ever witness. “[T]hese phenomena really exist and it is no longer possible for me to doubt it,” he proclaimed. “There is here in my opinion, a whole domain of entirely new facts and physical states in space of which we have no conception.”

Marie does not appear to have been as intrigued by Palladino as her husband, according to Susan Quinn, author of Marie Curie: A Life. She had other demands on her time and energy, including her two young children and the intense public attention that followed her Nobel Prize win. But at the very least, Marie doesn't seem to have come away from Palladino’s séances as a firm disbeliever in the possibility of a spirit world—because after Pierre died, she continued to communicate with him.

A Message from Beyond

Marie Curie stands in her laboratory in 1912.Wikimedia Commons // Public Domain

Though he had been ill for some time due to what we now understand was radiation poisoning, Pierre’s death at the age of 46 was sudden and terrible.

While crossing a busy Paris street, he slipped and fell under a horse-drawn wagon, dying instantly when one of the wheels crushed his skull. Marie was devastated. Her daughter Eve would later remember that from the day Pierre died, “Madame Curie … became not only a widow, but at the same time a pitiful and incurably lonely woman.” Over the next year, Marie kept a diary in which she unburdened her intimate and sorrowful thoughts. She addressed most of the entries to Pierre, which Goldsmith writes, is “striking and odd—until one realizes that the Curies … believed in spiritualism, a basic tenet of which is the ability to communicate with those who have ‘passed over.’”

Shortly after Pierre’s death, Marie took to her diary to reflect on the funeral. “I put my head against [the coffin],” she wrote, in a one-sided conversation with her late husband. “[A]nd in great distress … I spoke to you. I told you that I loved you and that I had always loved you with all my heart.” And then something strange happened: “It seemed to me that from this cold contact of my forehead with the casket something came to me, something like a calm and an intuition that I would yet find the courage to live.”

Perhaps, Marie writes, it was just an “illusion.” Or was it, she asks her husband, an “accumulation of energy coming from you?”