On January 24, 1925, a group of astronomers from around the world met at the Van Vleck Observatory in Middletown, Connecticut. The occasion: a total solar eclipse passing directly over the Observatory.

It’s rare for an eclipse to pass over a permanent observatory, as occurred in 1925. In a solar eclipse, the Moon casts a shadow over the Earth. Because the Moon is small relative to the size of the Earth, this shadow covers only a small fraction of the Earth’s surface—typically in rural regions. Without any permanent telescopes, astronomers went on “eclipse expeditions,” bringing their own portable equipment and tents.

Because total eclipses over permanent observatories are rare, and because they only cover a narrow band along the Earth’s surface, the astronomers visiting the Van Vleck Observatory came from around the world. A group from the University of Virginia attached a tent (pictured in the background) to the side of the Observatory. Two European astronomers—Charles Lassovsky of the Hungarian National Observatory in Budapest, Hungary; and George Lassovsky of the University of Louvain in Louvain-la-Neuve, Belgium—sailed to the United States to visit the Observatory. A group of astronomers traveled from Mount Wilson Observatory in Mount Wilson, California.

The goal of these astronomers was to experimentally verify, test, and build from many recent scientific theories. In the prior fifteen years, scientists had discovered a number of theories fundamental to modern astronomy. In 1913, Niels Bohr proposed a theory that explained why hydrogen emits light only at certain wavelengths. In 1915, Albert Einstein published his theory of general relativity. Solar eclipses provided perfect opportunities to test these theories.

Scientists identified gases using spectra taken during solar eclipses even before Bohr proposed his atomic model. In 1868, P.J.C. Hanssen discovered a gas associated with solar spectral lines—which work as an element’s “fingerprint”— that had not yet been seen in the laboratory. As a result, he named the new element “helium,” after Helios, the Greek Sun god. Other scientists followed this finding by discovering other “unknown” elements — most of them, like the famed element “coronium”, were actually already known elements that emitted light at particularly high energy. Throughout the early 20th-century, scientists used solar eclipses to learn about the atomic structure of many elements on the periodic table.

Einstein’s general theory of relativity had an especially great impact on solar eclipse research. Einstein’s theory held that gravity bends the path of light. Stars whose light passes by the Sun are only visible during solar eclipses. In 1914, an astronomer tried to test an initial version of Einstein’s theory, but was unable to do so because of World War I. Then, in 1919, Sir Arthur Eddington confirmed Einstein’s predictions at a solar eclipse expedition in South Africa. His results were confirmed in 1922.

Astronomers at Wesleyan University utilized both Bohr’s and Einstein’s theories. According to The New York Times, astronomers tested Einstein’s theory of general relativity. Other astronomers visiting Wesleyan also allegedly discovered a new gas during the eclipse, Wesleyan Astronomy Professor Frederick Slocum claimed. However, the excitement surrounding the findings appears to have been short-lived. Of course, this was not the first confirmation of Einstein’s theory, and Slocum would not name the gas or describe its properties. It is likely that, like coronium, the element was merely a highly ionized version of an already known element.