How a Solar Eclipse Revolutionized Our Understanding of the Universe

Up until the early 20th century, the laws that our universe abided by were best described by Isaac Newton in his Philosophiae naturalis principia mathematica. Newton’s principles still hold true for the most part, as they are the basis of many introductory classical mechanics classes today. Despite being able to model the laws of our universe for the most part, they began to break down when used to describe large-scale phenomena. German Physicist Albert Einstein wanted a model that could describe the laws of the universe in their entirety, so he produced the theory of general relativity, which he published in 1915. One key aspect of the theory of general relativity is that space and time are interwoven and form what is known as the fabric of space-time, which can be warped by massive objects. Because of this, general relativity states that light should be bent when it passes through distorted space-time around these massive objects. The apparent, or observed position of a star may not be its actual location if it is in the background of a much larger object.

Apparent versus actual position of a star behind a foreground white dwarf

Because of limits in technology, the only object large and near enough to use to observe this phenomena was the Sun. The Sun is too bright to be able to observe any stars in the background, but a total solar eclipse on May 29th of 1919 was the perfect opportunity to observe these background stars. Astronomers who conducted the observations knew the actual positions of the stars that were behind the sun during the eclipse. The eclipse lasted for long enough for astronomers to observe that these stars appeared ever so slightly away from their actual locations, but the observations were enough evidence to confirm Einstein’s theory of general relativity.

Image from the May 29th 1919 eclipse

General relativity has yet to be superseded by a better theory, and for the time being best describes the nature of our universe. Had it not been for this eclipse, one can wonder how long it would have taken general relativity to be confirmed, or if it was even capable of gaining the support of other physicists at the time.

2 thoughts on “How a Solar Eclipse Revolutionized Our Understanding of the Universe

  1. This is a fascinating note in the history of science. It’s worth noting that since this eclipse was largely visible in the Southern Hemisphere, there had to be expeditions sent with scientific equipment across the globe (specifically Brazil and off the coast of Africa). Probably the next most famous test other than the Eddington experiments is the test of the gravitational redshift, which didn’t happen until the 1970’s. The usage of an eclipse possibly advanced physics by decades!

    Liked by 1 person

    1. There were tests done on the 2017 eclipse as well but I admit I have not looked for any results yet (so much science, so little time!). The path of totality for 2017 was a lot easier to reach than the 1918 eclipse!


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