The Eclipse that made Einstein one of the Most Famous Scientist in the World.
The story about one of the most famous eclipses for Physic history.
Recently in North America, on April 8th 2024, we were able to witness a beautiful astronomical phenomenon: a total solar eclipse. An event that millions of people were able to appreciate in Mexico, USA, and Canada.
But perhaps, because of the title, you may be wondering how the interposition of the Moon between the Earth and the Sun could turn a German physicist into a popular icon for science.
Theory of General Relativity
In 1915, Einstein proposed the theory of general relativity, using nothing more than mathematical calculations. This theory, in very basic terms, proposed a new conceptualization of Isaac Newton’s laws of gravity. Einstein challenged the prevailing ideas in contemporary physics and established certain key ideas in his theory.
- Light has an absolute speed of 300,000 km/sec. (which had previously been calculated by the experiments of Michelson and Morley)[1].
- There is an equivalence between mass and energy, relative to the speed of light.
- There is an intrinsic relationship between space and time.
Einstein proposed that time was relative depending on the observer and that this could be directly affected by the mass of objects located in space. This concept is generally explained as a trampoline or a sheet of fabric extended in space, this theoretical trampoline deforms depending on the mass of the objects. The greater the mass of the object, the greater the curvature it exerts on the fabric (space-time) and this causes the interaction and movement of adjacent objects on the trampoline to undergo changes in their own trajectories. Einstein was criticized with skepticism for these novel ideas that could not be experimentally verified at the time [2].
It was not until 1919 (4 years later) that a group of scientists such as Frank Dyson and Arthur Eddington, prestigious British astronomers in the academy who understood Einstein’s ideas, set about experimentally testing the theory of relativity.
In search of a solar eclipse
To test the theory, they used a total solar eclipse that would occur on May 29th of 1919, in a narrow strip that would run from the Pacific Ocean, through Brazil, the Atlantic Ocean and Equatorial Africa to the Indian Ocean, as their laboratory. The idea was simple: to study the influence of the Sun’s gravitational field on a ray of light from the stars and thus verify the prediction of the general theory of relativity. According to Einstein’s theory, the rays of light from the stars would undergo a deflection of 1.74 arcseconds due to the deformation of the curvature of spacetime that the Sun exerts. Eddington also stated that if photographs of the eclipse could be taken, they could be compared with the photos that had already been taken with the Greenwich and Oxford telescopes, which showed the same stars in their real positions, without the possible distortion caused by the Sun’s gravitational field [3].
Thus, they set off on two expeditions to different locations to make the necessary preparations for the proper observation of the eclipse. It lasted 6 minutes and 51 seconds (one of the longest of the 20th century). During the eclipse, many photographs were taken of the stars around the Sun’s corona (which under normal conditions would not be visible due to sunlight). Eddington was responsible for analyzing the data taken on Príncipe Island (off the coast of what is now the Gulf of Guinea in Africa), while Dyson was responsible for the data from Sobral (on the northeast coast of Brazil).
Testing the theory
They compared the real and apparent positions of thirteen stars and the conclusion was exactly what they had expected. The analysis of the measurements obtained of the deflection of the rays of light confirmed the influence of the gravitational field on light, as predicted by Einstein’s theory [4, 5, 6].
The first experimental verification of his theory gave Einstein the international recognition that suddenly led him to become one of the most recognized icons in the history of science.
Without a doubt, I find this story of science fascinating, of how some photos taken during an eclipse in the Atlantic Ocean more than 100 years ago led to the verification of the mathematical calculous of a theory that would change the concepts on physics until that moment. And would led to aplications and modern discoveries such as GPS, prediction of astronomical events to advances on 0ther sciences as epigenetics.
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