In Dan Brown's Da Vinci Code, a professor stumbles upon secrets hidden in Leonardo Da Vinci's work that threatened the common view of the origin of Christianity. The book follows the conspiracy to cover up this discovery. Dan Brown could have saved himself a lot of trouble. He didn't need to create any characters or invent conspiracies. There was a real Da Vinci Code story. It had twists and turns like the fiction and an equally surprising ending. The real Da Vinci Code story was ended by a Nobel Prize winning nuclear physicist, Louis de Broglie.
In the early twentieth century, a professor named Pierre Duhem stumbled upon secrets hidden in Leonardo Da Vinci's work that threatened common views on the origins of modern science. A conspiracy of powerful figures in academia prevented his work from being published. Sometimes truth is stranger than fiction. The real Da Vinci Code involved a tug of war between some of the most famous historians and physicists from the early twentieth century over the censorship of Duhem's work. The figures involved included Louis de Broglie, the Nobel Prize winning physicist, but also George Sarton, the father of the Modern History of Science. The heroine of the story wasn't famous however; she was a farm-girl from the south of France. Pierre Duhem's daughter, Helene, decided that her father's unpublished work must be published. This meant taking on the academic elites at Harvard and the University of Paris.
Pierre Duhem was a rare genius. One hundred years after his death, his name is still mentioned in thermodynamics texts. But what is unusual for a modern academic is that he was important to more than one discipline. You will also find his name in philosophy [_1_] , economics and history of science textbooks. One can hardly think of a better candidate for a historian of science; accomplished in both Math and Physics, meticulous in his research, and aware of both the cultural and philosophical issues in science.
Pierre Duhem had already established an international reputation in physics and philosophy when he turned his attention to the history of science. His early historical work was well received. He wrote books on the history of mechanics and several on Leonardo da Vinci before attempting the massive 10-volume System du Monde. The first volume, dealing with Greek science, was sent to Isis. Isis was the most important journal on the history of science at that time. George Sarton, its editor, is commonly referred to as the father of the history of science. Duhem's work received a very positive review and George Sarton even let Duhem know that he was looking forward to the other volumes.
Pierre Duhem, renowned philosopher, theoretical physicist and meticulous researcher was rarely mentioned again in Isis while George Sarton was editor. The first volume of System du Monde was the last volume that would be reviewed. Duhem had become a persona non grata. Duhem had uncovered forbidden knowledge. Historians of science from that time were heavily invested in the theme that the church and science were in permanent conflict. Duhem's work suggested that science may have originated centuries earlier than thought, during a time when the church was dominant.
Pierre Duhem's road to being shunned by the historians of the day was innocent enough. His early investigations into the history of science were centered around the scientific works of Leonardo da Vinci. And it is clear that he started his investigations with the same bias as other historians of his day: that important scientific developments had not occurred in Christian Europe before da Vinci [_2_] . But Duhem was the type that would follow a trail wherever it led. If Leonardo da Vinci referred to a source in his works, he would track it down. If that source referred to another source, he would follow it too. This lead Duhem from Da Vinci to medieval physicists that were proposing concepts associated with more modern scientists such as Galileo and Newton. Duhem had found modern science where he wasn't supposed to. This was a threat to the status quo, especially since Duhem's credentials in physics could not be challenged. Duhem died before the final volumes of System du Monde were published. The manuscripts for the final volumes were blocked from publication and the name of this promising new historian was rarely mentioned in Isis over the next forty years.
What was in the Da Vinci Codices that was so threatening. It was the Parisian Doctors. This was a group of priests and bishops from the fourteenth century that had written extensively on classical mechanics. They had formulated Newton's First Law of Motion almost three hundred years before Newton had [_3_] . They had defined constantly accelerated motion centuries before Galileo. Galileo's description and geometric proof of the Odd Number Rule was largely the same as those of the Parisian Doctor, Bishop Oresme. We know that Galileo knew of the Parisian Doctors' work from his own writings. There was another threat posed by the Doctors. There was a direct line from the Parisian Doctors to another group, the Oxford Calculators (see The Calculatores). This was another group of priests and bishops studying classical mechanics. They had developed the mean speed theorem centuries before Galileo had proposed it (see How original is Galileo’s work on kinematics?).
The answer to the "Duhem Problem" was to censor his work. Academic conspiracy theories sound no more believable than the Da Vinci Code's Priory of Sion, a twentieth century hoax that even claims Dan Brown as a victim. But the academic censorship of Duhem's work has credible witnesses. Duhem's publisher, Hermann et Cie, refused to publish the final volumes of his Systeme du Monde. The excuse given was financial hardship. The real reason why Duhem's work would not be published was divulged by an insider into the workings of the French scientific establishment; the head of the Institute d'Histoire des Sciences at the Sorbonne, Abel Rey. It was not financial concerns. Hermann et Cie was being pressured by very powerful anti-clerical elements in government and academe not to promise publication of his work. The information in the manuscripts was not something they wanted published. His works showed that significant advances in the science of mechanics had occured well before the "Scientific Revolution" and during a time when the church was the central influence on society [_4_] . Abel Rey is one of the heroes of the story. Abel Rey was himself anti-clerical. This did not stop him from supporting Helene Duhem's 40 year long fight to publish her father's last works.
The censorship didn't stop with a hostile publisher. Duhem had crossed the line with the second volume of the Systeme du Monde. George Sarton, the editor of Isis, believed strongly that Science and Christianity conflict. Duhem's name would rarely be mentioned in Isis while Sarton was editor. Sarton allowed the publication of a virulent personal attack on one of the giants of the history of science by his graduate student. The student even suggested that one of the great physicists of the late nineteenth century didn't fully grasp the physics he was discussing [_5_] . Sarton, like Duhem, was a specialist in Medieval History. Some of his own works did not reference Duhem at all. We know this was not due to either the quality or volume of the work. Even with the censorship of the last five volumes of the Systeme du Monde, Duhem left behind a huge volume of work. Modern historians reference Duhem more often than Sarton and many of his contemporaries (see Sarton and the Isis Files).
If the managers at Hermann Cie and George Sarton were successful in their censorship of Pierre Duhem, how do we know of Pierre Duhem? When Duhem died in 1916, he left behind a daughter that was every bit as stubborn as he was. She was also very dedicated to her father. She knew that he had left 5 unpublished manuscripts on his death. She also knew that these manuscripts were in publishable form. The French Academy of Sciences had analyzed them. Duhem died during World War I. Understandably, publishing manuscripts on medieval history is not a priority during a war. The end of war didn't seem to help matters. Hermann et Cie. always had an excuse. This went on for two decades. Helene Duhem never stopped trying to find allies to pressure Hermann to publish. The low point came with World War II, when she feared that the manuscripts would be lost. With the end of the war came more hope. Hermann et Cie. still made excuses. Helene, not knowing how to quit, enlisted the support of one of the great nuclear physicists of the twentieth century, Louis de Broglie. Even the stature of this Nobel laureate was not enough. de Broglie had to use his position as the Secretary of the French Academy of Sciences to threaten Hermann with a lawsuit. The final volumes were published in March, 1954. The real da Vinci Code story had ended; 38 years after it began.