General theory of relativity, once nicely described by one of my lecturers as the equivalent of the Beethoven’s 9th symphony in physics , is undoubtedly one of the pillars of modern physics. The history of the development of this theory is well documented, so, today, I would like to look at another side of the history of GR — the history as documented in quotes. Here are a few crucial quotes, which unfold the history of GR.
”I was sitting in a chair in the patent office at Bern when all of sudden a thought occurred to me: If a person falls freely he will not feel his own weight. I was startled. This simple thought made a deep impression on me.”
This quote depicts one of the most important moments in the development of GR. What Einstein is talking about here is, of course, the principle of equivalence — one of the cornerstones of the theory. By finding parallels between acceleration and gravitation Einstein was able to overcome many great obstacles when developing GR.
”Then I would feel sorry for the good Lord”
Einstein answered, when asked by a journalist what would happen if the upcoming expedition to test GR would prove the theory incorrect. In 1919, Sir Arthur Eddington led expeditions to Brazil and to the island of Principe, aiming to observe solar eclipses, which would offer a unique opportunity to observe whether the path of light would be bent by the gravitational field of the Sun. It is evident that by 1919 Einstein developed the theory enough to be absolutely confident in it being correct.
”Who’s the third?”
This was said by the great astronomer Arthur Eddington in 1919, when he was asked if it was true that only 3 people understood general relativity. Needless to say, it wasn’t true, but the quote nicely illustrates how revolutionary the theory was back then. Like quantum mechanics, GR was too abstract and mathematically complex to be easily accessible to the general public.
“Time travel used to be thought of as just science fiction, but Einstein’s general theory of relativity allows for the possibility that we could warp space-time so much that you could go off in a rocket and return before you set out.”
One of the most mind-blowing consequences of the theory of special relativity was time dilation, the most famous example of which is the twin paradox. Through the twin paradox SR brought the idea of time travel from the realms of science fiction straight into science textbooks. GR, however, went one step further, and, at least theoretically, made time travel into the past possible. As Stephen Hawking points out in this quote, there exist certain solutions of the theory, which make it possible to arrive at a destination before leaving, which opens the gates for all kind of philosophical and physics paradoxes.
“I still can’t see how he thought of it”
This was said by the great scientist Richard Feynman, who was deeply fascinated by the theory of general relativity. Even though, throughout the years, GR became a part of the basic physics university education, the story of how exactly Einstein came up with the theory still remains a bit of a mystery.