Eclipses Have History Too

Headline in New York Times, Dec. 3, 1919.

Headline in New York Times, Dec. 3, 1919.

By Jennifer Vannette

Yesterday, like so many others, my family and I gazed at the sky to watch the Great American Eclipse of 2017. Waiting and looking, we began to share stories of past eclipses witnessed. My husband also shared a story of of how a combination of eclipse timing and geopolitics "saved" our understanding of science.

When one thinks of World War I and advancement in science, the tendency is to slip into a discussion of technological advances that brought about modern warfare, but before war broke out, scientists had their eyes turned to the stars.  On August 21, 1914, Europe experienced a total solar eclipse. Much like today, scientists traveled to the path of totality, which passed through Sweden, Germany and Ukraine. A team of British scientists led by Erwin Finlay-Freundlich traveled to Crimea to make measurements, but did not have the chance because WWI broke out and the team spent the war interned in Russia.

These scientists did not just want to observe an eclipse. They expected to disprove Albert Einstein's new theory of special relativity, which rubbed up against Newtonian theories. Einstein said that that space and time were not static; we observe things differently than each other, and the speed of light is the only constant. The question at the heart of this theory was whether light would bend due to the gravity of a massive object. As Universe Today explains, "...astronomers soon realized that the best time to catch this in action would be to measure the position of a star near the limb of the Sun — the most massive light bending object in our solar system — during a total solar eclipse." It's not that the light would only bend during an eclipse, but rather it was the only time the sun was blocked out enough to allow for detection. But, war did not wait for celestial observations and two eclipses during WWI in Europe, in 1914 and 1916 passed without data collection.

Now, had the observations been made in 1914, there would have been problems with the results aligning with Einstein's theory, and special relativity might have been challenged more greatly. However, in 1915, Einstein published a series of papers on general relativity, which corrected for some issues in special relativity. Space explains: "One of the key tenets of general relativity is that space is not static.  The motions of objects can change the structure of space. By contrast, in Newton's view of the universe, space is "inert."In Einstein's view, space is combined with another dimension — time — which creates a universe wide "fabric" called space-time. Objects travel through this fabric, which can be warped, bent and twisted by the masses and motions of objects within space-time." So, this time scientists wanted to try to observe the curve of light.

The next chance to take measurements in an attempt to prove or disprove general relativity came in 1919. At this point, resources could be dedicated to scientific activities and the Royal Society and the Royal Astronomical Society sent expeditions to Brazil and to the island of Principe, off the west coast of Africa to look for evidence of the light curving. The eclipse happened to be the longest of the the 20th Century at six minutes of totality. The Royal Societies analyzed the data and found Einstein's theories correct. The news was published in the New York Times on Dec. 3, 1919, and for the first time non-scientists learned of the new scientific theory.

As a historian, the story intrigued me, and a quick search to sort out some of the fuzzy details helped me realize that the history of science, left in the hands of scientists, can sometimes cause some confusion. The details are fuzzy because the stories are simply passed down as a fun aside. So this one comes with conflicting accounts. Some scientists related the anecdotes as WWI saving the theory of general relativity because due to errors, it might have been disproven in 1914. Because Einstein had time to revise and further consider relativity and publish more in 1915, this meant that the 1919 observation proved successful. Others argue that due to WWI, Einstein remained cut off from the scientific community and if it were not for Dutch and British scientists continuing to communicate with him, no one would have heard of his theories. Scientists naturally get caught up in the science, making it difficult to pin the story down. A brief search only yielded one book on the topic, and it is heavy on equations. However, critical understanding of how science is not developed in a vacuum (sorry, couldn't resist) but is truly affected by current events can make scientific understanding more accessible to the general public, and even help us contextualize current debates.

*Apologies to all scientists who would prefer better explanations of relativity.