The 1929 Solar Eclipse that challenged Einstein’s theory
A total solar eclipse is happening on 8th April 2024 across America. An eclipse 105 years ago verified Einstein’s calculation on the general relativity theory. But 10 years later, there were doubts on the theory from eclipse observation in Aceh.
In 1929, astronomers calculated that a solar eclipse would occur on May 9th, passing through Northern Sumatra and the Malay Peninsula. This event attracted several international expeditions to Medan for astronomical observations.
Solar eclipses provide an opportunity to validate Einstein’s theory of General Relativity, which proposes that gravity can bend light. According to Einstein’s 1915 theory, light, though massless, is influenced by gravity, causing it to curve near a massive object. This effect is observable during a solar eclipse, when the sun is obscured, allowing the observation of starlight bending near the sun. This phenomenon and the angle of deflection was confirmed during the May 1919 solar eclipse observed by English scientist Arthur Eddington in South America and Africa. Ten years later, the eclipse in Sumatra offered another chance to verify Einstein’s theory.
Prof. Erwin Finlay Freundlich led a scientific group from German consisting of six persons from the astrophysics Einstein Tower in Potsdam. Freundlich and colleagues have designed the most precise camera to capture pictures of stars around the sun. They brought 15,000 kg of instruments arriving in Belawan to be set up in Takengon. The expedition was financed by the Notgemeinschaft der Deutschen Wissenschaft (Emergency Association of German Science) and also some kind of support from the Dutch government through transportation discounts and local arrangements. A German meteorological expedition also joined the team to make systematic observations of the eclipse’s impact on weather.
Mrs Freundlich, the wife of Erwin, also joined the expedition “…, merely as housekeeper for members of the expedition. I shall see that they get the right kind of food and look after their comfort…”
The American expedition of 9 persons was led by Dr. John H. Miller, an experienced scientist who had observed seven previous solar eclipses. The team was considering whether to observe in Idi or Takengon. They decided to go to Takengon, which was a Dutch military station, as it was at a higher elevation of 3600 feet and would observe 4 minutes and 58 seconds of eclipse. They arrived at Belawan with their instruments and set up a headquarter at Hotel de Boer. It took two days to go to Takengon. The American camp was near the German camp. They set up a large camera to take photographs of the corona.
At the day of the eclipse in Takengon, in the morning, the sky was overcast but fortunately, the sky was clear during noon and the eclipse occurred at 12:47 PM. The American and German teams were successful in taking pictures and gathering data. A Japanese team in Perlak Atjeh also reported successful observations.
However the Dutch expedition led by Dr. Vanderbilt in Idi was not successful. Despite being the host with meticulous planning and organisation, their efforts at Idi on the northeast coast were thwarted by heavy cloud cover. There were also observations in Kedah (Malaya), Siam, Indochina and the Philippines by British, American, German, French and Japanese groups. All of the observations suffered from cloudy sky and the only clear observation was in Takengon.
Numerous people, including the governor of Sumatra, journeyed to Langsa to witness the eclipse, enjoying a clear view of the spectacle. As the sky progressively darkened, they observed striking light streaks and the sun’s corona during the total eclipse.
In Medan, the weather was unusually hot with no rain, some planters even suggest a connection between this weather pattern and the solar eclipse. The eclipse was only partial in Medan, but it still drew many spectators outdoors. Around 1 PM, there was a noticeable drop in temperature, providing relief from the usual heat. The eclipse’s peak brought darkness and in the Chinese quarter people created a cacophony of sounds using fireworks, drums, and trumpets. This tradition stems from the belief that eclipses are caused by a malevolent spirit or dragon consuming the sun, which can be repelled by noise. Notably, Venus was visible to the naked eye during the eclipse in Medan.
A day later, Einstein received the news in Berlin and said “the successful observation at Sumatra of the sun’s eclipse yesterday constitutes enhanced confirmation of the theory of relativity, which, however, has been tested several times before.”
It took the German team, led by Freundlich, a year to complete the calculation. They found out that the light deflection was 2.24 arc second, which was larger than Einstein’s theory of 1.75 arc second. Einstein found this result irritating as there was a doubt on Eddington’s calculation which verified Einstein’s theory ten years before and made Einstein famous.
Two years later, Einstein acknowledged in Berlin in a speech to the Society of Physics that his calculations regarding the deflection of light rays needed a revision as a result of the examination of the solar eclipse photographs taken in Sumatra.
It is now acknowledged that the errors of stars photography during eclipse had been too large. Astronomers faced issues in repeating experiments due to the unpredictable nature of eclipses. The success of the eclipse experiment in 1919, which supported Einstein’s theory, is considered as a lucky chance that boosted Einstein’s reputation.
The 1929 solar eclipse that passed over Northern Sumatra highlighted Medan as a transit or gateway to the region. Medan’s cultural diversity, with local traditions and beliefs surfacing amidst the scientific excitement. However most of the population did not understand the significance of the event as science was still a western hegemony. It took another twenty years before Indonesia started its formal astronomy faculty.