Dr. Francesc Ferrer lectures on an Eclipse about (Lydia Nicholson | Student Life)

Dr. Francesc Ferrer, Associate Professor of Physics, presented “The Eclipse That Made Einstein World-Famous” as part of the Saturday Science Lecture series leading up to the April 8 eclipse on Saturday, Feb. 24. 

Ferrer explained how Einstein’s 1915 General Theory of Relativity was proved by measuring the bending of light, which was only possible during a solar eclipse. 

According to Ferrer, an important and interesting character in the history of the General Relativity Theory was Carl Gauss, a mathematician that Ferrer described as “more powerful than AI” and “the equivalent of Newton for math.” Ferrer said that Gauss did not let any of his sons study physics, because they would damage his name.

According to Ferrer, Gauss conducted an experiment to prove that space is generally Euclidean, which means it is, on average, flat. Ferrer said this experiment would eventually prove vital to Einstein’s General Relativity Theory. 

“He was measuring the curvature of the space itself, it’s something that you cannot imagine because you would need four dimensions to see,” Ferrer said. “He was trying to measure the curvature of the three dimensional space from within it.”

Ferrer then discussed Einstein himself and the four papers that he published in 1905. These papers included his famous E = MC2 equation, proved the existence of atoms, and explained special relativity, which is the idea that time relatively slows at high speeds.

Ferrer said that Einstein’s work in these subject areas was not highly recognized at the time. 

“So you would think, you write four papers, he must be super famous, right?” Ferrer said, “The answer is no. That was 1905, he only got the Nobel Prize in 1921, and only for the photoelectric effect. At that time, there were still doubts about the theory of special relativity. And, nobody was particularly interested, these people didn’t understand this paper very much.”

Ferrer said that Einstein was inspired to write his general theory of relativity because he was asked to do a review of his special theory of relativity for a contemporary physics book.

“Sometimes you think you understand something until you have to explain it,” Ferrer said, “And Einstein realized that his special relativity theory did not agree well with the F = mg of Newton, the gravitational force.”

Ferrer then gave a brief overview of general relativity and how it affects light. He said that Einstein describes an elevator in two different situations: at rest on Earth’s surface where it and everything in it is affected by Earth’s gravity, 9.8m/s2, and an elevator in space accelerating at 9.8 m/s2. According to Einstein, these two situations are exactly equivalent.

“The bottom line is if you want to understand what will happen to light close to a planet or the sun, it’s very easy, the only thing you need to do is imagine what would happen to a planet on a freely falling elevator,” Ferrer said. 

Hannah Kinzer, a Ph.D. student in the Brown school, said that she appreciated Ferrer’s visual explanations.

“It was really cool to see the visualizations,” Kinzer said, “It was really cool to see how [they’re] representing different observations in a way that the human brain can understand and grasp.”

Ferrer then explained what the effect of gravity on light means for solar eclipses. 

“Now, this bending of light has a consequence, and this is the consequence that we want to measure [with the eclipse],” Ferrer said, “Imagine a star, and of course it starts to emit light, and it just so happens that [this light] passes very close to the sun.”

Ferrer said that the sun will bend this light due to its massive gravitational field and will alter the light’s path to the Earth. According to Ferrer, this creates a discrepancy between the apparent star location and the actual star location.

“If you calculate that effect, it’s something that was more or less in reach of the accuracy of telescopes at the time,” Ferrer said, “The only problem is that…the star needs to be right behind the sun, so the only way you can make that experiment is if you have a total solar eclipse covering the sun, and, during those minutes, you are able to see what’s behind the sun.”

However, Ferrer said that Einstein was not well known and did not have the resources to travel to watch a solar eclipse. He said that the first opportunity for an eclipse to be measured, in 1912, was spoiled by rain and location issues, so no pictures were taken. 

In 1914, Einstein paid to send a team to Crimea, Ferrer said, to observe the eclipse, but World War 1 started and the team was arrested and the equipment confiscated.

“During [1914], Einstein was very isolated, and this allowed him to actually finish his theory of gravity,” Ferrer said, “He realized that when he first calculated the deflection of light he had made a mistake, so in a sense he was very lucky that both eclipses failed.”

Ferrer explained the mistake Einstein made in his original theory.

“He missed half of the reflection because in 1915 he found out that the reason light is curved is because the spacetime itself is curved,” Ferrer said. “He had to use the tools of Gauss.”

Despite space being, on average, flat, it can be locally distorted by large amounts of mass.

Ferrer said that, around 1915, a physicist named Arthur Eddington learned about Einstein while in the neutral Netherlands and decided they should become friends. Ferrer said that Eddington became exempted from war due to his work and the importance of proving General Relativity and that Einstein sent Eddington to measure the “crucial” 1919 eclipse. 

Ferrer said that, after studying the eclipse, Eddington realized that Einstein was right and that the stars “are not where they seem to be,” as Eddington later said.

Dana Gray, a local entrepreneur in attendance, said she was interested in the interactions of scientists with each other and with the general public.

“The personal information about the relationship between the scientists was really interesting, and how they sort of had this banter of competition was fun,” Gray said. “You know, knowing that the war had played into how the information and credibility of the scientists was viewed.”

Ferrer said that radio measurements of Venus behind and in front of the sun also confirmed Einstein’s findings. He explained that this method of observing light bending can help physicists measure the mass of star clusters.

Ferrer ended his speech by quoting Eddington. 

“Oh leave the Wise our measures to collate. One thing at least is certain, light has weight. One thing is certain and the rest is debate. Light rays, when near the Sun, do not go straight,” Ferrer said.

Dr. Manel Errando, the Director of Undergraduate Studies in Physics, who helps organize the Saturday Science Lecture Series, says that they are an important way to make science accessible.

“The idea is just to bring people in so that they think about science and get excited,” Errando said. “So you will see kids, and maybe they will get interested in their science classes a bit more.”

Janna Angeles, a physics Ph.D. student, said she appreciates accessibility in science.

“It’s actually geared towards the general public,” Angeles said, “There’s not a bunch of information that will overwhelm them, they just kind of focus on the significance of a certain event.”