Einstein 1905: The Standard of Greatness

"Einstein published five papers that year. All of them are considered of great value. The paper that Einstein regarded as the most revolutionary of his work in 1905 was actually about quantum theory. There was another paper about Brownian motion. He showed that the phenomenon of Brownian motion—which had been known for almost 100 years—was actually due to atoms bombarding particles. This was considered proof of the atomic theory of matter by his fellow physicists — the first time that atoms had really been proved to exist. Then, the last of the five papers concerned probably the most famous equation in science: E=mc2. This came out of his first paper on relativity and was published at the end of 1905. As everyone knows, E=mc2 is the basis for what happens with nuclear energy and the atomic bomb later in the century. Yes, and c is the speed of light. So, with E=mc2, you can immediately see that the amount of energy is enormous from a small amount of matter because c is such a large number. So, E=mc2 implies a very large amount of energy from a small amount of matter through the process of atomic fission and fusion which Einstein didn’t know about in 1905. Fission was not discovered until later — just before the Second World War , in fact. It’s a response to Newton’s idea of absolute time and absolute space which Einstein rejected after thinking about it deeply. John Rigden puts it quite well in his book. He says, “A world with absolute space existing apart from absolute time would turn into a world where space and time are joined”. This theory of relativity led to the concept of space-time which is a key thought in general relativity. It’s not easy to explain relativity in a few words, but it rejects absolute time and space, leading to the idea that all motion had to be defined relative to a coordinate system — and that different coordinate systems had to be compared. General relativity was much more comprehensive, it included gravitation and acceleration. In fact, Einstein’s great idea about general relativity was that gravitation and acceleration were equivalent and that we must build our idea of the universe on that thought, rather than regarding them as independent, as Newton did. Yes, the curvature of the rubber sheet is a way of expressing—not literally, it’s a symbol—the curvature of space-time. The experimental proof of general relativity came only later. Probably the most famous aspect of the experimental proof is the bending of a light-ray by the gravitational field of the sun. The light emitted by distant stars was observed to be bent by the gravitational field of the sun in 1919 during an astronomical expedition led by Sir Arthur Eddington, a British astronomer. After that expedition, physicists started to take general relativity much more seriously. There were other experimental proofs as well, but that was the beginning of the idea that general relativity was correct. Before that, it was unproven and Einstein asked astronomers to go looking for it. That’s what happened in 1919. Astronomers were able to back up his theory with observations. The whole idea of the Big Bang has been explained, to a great extent, in terms of general relativity. This came much later than Einstein of course — he was dead by then. General relativity also explains the existence of black holes. Einstein didn’t think they existed, but, since the 1960s, experimental proofs have been found that they do. The whole structure of space and time which Newton imagined, an absolute coordinate system, has been abandoned in favour of a curved space-time formulation. That’s really the result of Einstein’s work. He was certainly very human and had many failings as well as an extraordinary scientific imagination. Scholars have looked closely at what Einstein was doing in the years up to 1905, there’s not enough evidence to be sure. There were a few letters to his wife, and he published a little bit. There is this feeling that it came out of the blue. It obviously didn’t. No genius works from a sudden eureka moment and it’s not like that, even with Einstein. The problem is that we don’t really know exactly what he was reading and how his thought process worked. What we do know is what he published in 1905 and that he was fascinated by contradictions in physics. He imagined chasing a light-ray in his mind and asked what a light-ray would look like if you caught up with it and came to the conclusion that it’s an impossible physical situation. That, according to Maxwell’s laws of electromagnetism, there was no such thing as catching a light-ray. From that, he concluded that light always moves at a constant speed — independent of the coordinate system you were using to measure it with. It didn’t matter how fast an observer moved, light would always move at a constant speed faster than the observer. “Einstein’s great idea about general relativity was that gravitation and acceleration were equivalent and that we must build our idea of the universe on that thought.” Another contradiction that fascinated him was to do with magnetism and electric charge. He imagined that if you had a stationary charge observed by a stationary observer, there would be no magnetic field which could be observed with a compass. But, if you kept the stationary charge and then the observer started to move, by Maxwell’s definition of electromagnetism, he/she would observe a magnetic field with a compass. So which was true? Was there a magnetic field or wasn’t there? He said that’s a contradiction, we have to resolve it. And he did resolve it, with his theory of relativity. Yes, he did. It was fruitful for his imagination. He liked contradictions and found them stimulating. That’s one of the strength of Rigden’s book. With practically no mathematics, he manages to show how various contradictions were perceived by Einstein and then used to create these various papers during that year. Rigden is very good at explaining it in clear language with historical anecdotes nicely integrated into the text."