Astronomers in a Chemists’ War

Battery C, 6th Field Artillery. Beaumont, France. 1918.

In August 1914, as the ‘Great War’ began, a pair of French scientists started working on a machine to detect enemy artillery fire using recorded sound. Charles Nordmann, the leader of the two and a career astronomer, was best known for his failed attempts at the turn of the century to detect solar radio emissions. His partner Lucien Bull had a medical background and prior to his work with the French military, was actively working on a device to record the human heartbeat. World War I is often called the ‘chemists’ war’ owing to contemporary developments in nitrogen fixation and the use of poisonous gases as well as synthetic fuels, but the science of modern warfare was cross-disciplinary and far reaching.

Five days after the assassination of Archduke Franz Ferdinand on July 28, 1914, Germany declared war on France. Though the conflict began in Eastern Europe, and ultimately involved 30 nations across six continents, German military strategy resulted in a faster mobilization of resources in the west with the immediate invasion of Luxembourg and Belgium. As a result, the first battles were fought on the western front, and it remained the scene of some of the most intense fighting for the duration of the war. In the war’s opening weeks, Nordmann left his position at the Paris Observatory and enlisted in the French artillery where he quickly developed a method to locate enemy guns by calculating the time between the landfall of a shell at different points along a measured a base. Under Bull’s patronage, he began to develop a technological solution that would supersede human observation.

Artillery Sound Ranging Schematic

Nordmann’s efforts attracted the attention of British military officials. Despite his ensuing failure to construct an accurate sound ranging machine, they were intrigued enough by his acoustic methodology to set up their own field experiments under the direction of William Lawrence Bragg. Nordmann’s attempts depended on field microphones and measuring instruments, but the cannon fire of the heavy artillery guns was often too low for easy detection. The Australian-born British physicist Bragg was (and remains) the youngest ever Nobel Laureate in physics, having won the award in 1915 at 25 years old for his work in x-ray crystallography, and it was the British team that made sound ranging an effective weapon in artillery war.

In June 1916, Bragg and his colleagues developed a platinum wiring system connected to field microphones built into repurposed artillery boxes that heated and cooled to create a signal pulse for low-frequency booms. Unlike previous carbon microphones, the wire system could distinguish sounds between the launch of the gun and the reverberating boom generated by mortars in the air. It could even distinguish between types of artillery and was accurate enough to pinpoint the location of enemy batteries within 10 meters based on the length of time between the gun’s firing and the recording of the sound on various microphones stretched out over the battlefield. The technology was quickly implemented in every unit of the British Army.

French artillery sound ranging system. Purchased by Finland in 1927. Photographed in Hämeenlinna artillery museum.

When the war began, President Woodrow Wilson declared that the United States would remain neutral and advocated for a policy of nonintervention until the sinking of the Lusitania by a German U-boat and the interception of the Zimmerman telegram alluding to a potential alliance between Germany and Mexico swayed public opinion. The U.S. officially entered the war on April 6, 1917 and, almost immediately, a commission of French scientists traveled to the United States to educate American military officials on the newer applications of science to warfare. Sound ranging was among the key topics and, as success demanded operational personnel with technical training, a Princeton physicist named Augustus Trowbridge was elected to be the technical director of the American Sound and Flash Ranging Service. Trowbridge recruited many of his own colleagues for help, among them astronomer Henry Norris Russell.

The Director of the Peyton Observatory at Princeton since 1912, Russell was an ardent researcher. The details of managing the observatory often fell outside his interests, and in his long tenure he accepted relatively few graduate students, though Harlow Shapley and Donald Menzel were among the few notable exceptions. By the time Russell joined Princeton’s war research committee, Trowbridge had already toured the western front in Europe to examine current sound ranging systems in action, and he’d resolved to create a more efficient portable alternative. Trowbridge and Harvard physicist Theodore Lyman handled practical operations on the battlefield, and recruited Russell to create a more efficient means of triangulating the data. Russell approached the challenge enthusiastically.

Henry Norris Russell, c. 1921

In the fall of 1917, Russell excused himself from teaching and put his personal research interests on hold in favor of aiding in the war effort. In a letter Edward Pickering, the Director of the Harvard College Observatory, Russell shared that he was instead “devising methods for observing the parallax of hostile artillery. It is quite as interesting as the other kind of parallax work… and at present it appeals to me as more immediately useful.” By the end of the year, he was regularly commuting to the Jersey coast to work with a team of Army Signal Corps engineers. Russell soon resigned from his fellowship at Princeton to accept a position in the Signal Officer’s Reserve Corps, eventually leaving for Europe to serve as the chief instructor in sound ranging at the Army Engineering School in Langres, France. In another letter to a colleague, written just after Russell turned over his managerial duties at the Observatory to an assistant, he predicted that “you won’t probably see many more astronomical papers of mine till we win.” Russell didn’t submit another academic paper for publication until well into 1919, when the war was indeed, won.

In Russell’s absence, and after two of his assistants followed his example in joining the war efforts, astronomical research at Princeton, most notably work on their lunar plate collection, stopped. In comparison, the Harvard College Observatory held a unique position among American scientific institutions during the First World War due to the relatively high number of women under Pickering’s employ. Though women could serve in nursing corps, there were few (if any) opportunities for women in military science, and plates continued to be taken at Harvard despite wartime inconsistencies elsewhere. Days after the Armistice of November 11, 1918, signifying the end of the war, it was Pickering who wrote to Russell about the career he’d left behind, asking: “Have you forgotten that you are the active executive of the Astronomy Committee of the National Research Council?” In the letter, Pickering suggested Russell’s post-war reports should highlight the specific contributions of astronomers towards winning the war. To his mind, “the training of astronomers has rendered them especially fitted for solving many problems essential to the successful prosecution of war.”

Edward Pickering died three months later after a forty-two year tenure as Director of the Harvard College Observatory, which put him at the forefront of astronomical study in both the United States and abroad. As one Oxford astronomer wrote, “the King is dead.” For whoever came next, it would be a challenging act to follow. Despite the gap in his research, Russell’s brief interlude with the Army Signal Corp and his work to improve sound ranging techniques added to his reputation as “the man of greatest intellectual power” in the United States. When the time came to determine Pickering’s successor, committee members were split between Russell and his former graduate student Harlow Shapley, but Russell fielded the first offer. He declined, choosing instead to remain at the Peyton Observatory, and it was Shapley who relocated to Cambridge in 1921.

Bibliography

Bourne, J. M. (2001). Who’s who in World War I. London: Routledge.

Compton, K.T. “Biographical Memoir of Augustus Trowbridge, 1870-1934.”National Academy of Sciences of the United States of America, Biographical Memoirs, vol. 18, no. 10, 1937. http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/trowbridge-augustus.pdf.

DeVorkin, D. H. (2000). Henry Norris Russell: Dean of American astronomers. Princeton, NJ: Princeton University Press.

How acoustics detected artillery in WWI. (2019, May 13). Retrieved June 25, 2020, from https://scienceblog.com/507836/how-acoustics-detected-artillery-in-wwi/.

Rawling, B. (2014). Surviving Trench Warfare: Technology and the Canadian Corps, 1914-1918. Toronto: University of Toronto Press.