© 2013 by Fernando Caracena
In 1887 two physicists from the two neighboring schools that would become Case Western Reserve University, Albert Michaelson and Edward Morley, performed the famous experiment bearing their names (The Michelson Morley Experiment), which detected no asymmetry in the propagation speed of light because of a supposed luminiferous aether drift. The impetus for this experiment came from Maxwell's formulation of electromagnetism, from which he predicted that there would be electromagnetic waves that travelled at a characteristic speed that was determined by the product of two fundamental constants, c=1/√(μ0 ε0), which could be experimentally measured or defined. The predicted speed of electromagnetic waves matched that of the speed of light. The problem posed by this prediction for electromagnetic waves was the predicted speed of electromagnetic waves was a universal constant, which would be valid in any inertial frame of reference according to tradition. This raised a question about in whether there was a preferred frame of reference, in which that predicted speed of light applied. If for example, you have a theory of water waves that predicts that they will move at a characteristic speed, and you have a fast boat, then you expect to see your travel over the surface of the water as affecting the speed that you measure for these water waves. You should see waves travel slower in the direction that the boat is travelling, and faster in the opposite direction; you should see an asymmetry in the propagation of water waves relative to your boat.
In analogy to waves moving over the surface of water, there was some discussion of electromagnetic waves' travel over some light-bearing medium, which was called the luminiferous aether. This aether was imagined to be a material medium much finer than ordinary matter, which formed a background against one could detect absolute motion. At this point, some physicists were willing to give up on the idea of relativity of inertial frames of reference that had deep roots going back to Galileo's and Newton's works.
It took a methodical thinker who thought deeply about simple things to solve the mystery surrounding the speed of light.
| Description | Albert Einstein during a lecture in Vienna in 1921 | ||||
| Date | 1921[1] | ||||
| Source | http://www.bhm.ch/de/news_04a.cfm?bid=4&jahr=2006 | ||||
| Author |
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| Permission |
Public Domain | ||||
Albert Einstein
Genius is no more than childhood recaptured at will, childhood equipped now with man's physical means to express itself, and with the analytical mind that enables it to bring order into the sum of experience, involuntarily amassed.
Baudelaire, Charles
As a child, Albert Einstein had been a slow learner. He began talking at the age of four, later than most children. Exasperated, his parents consulted a doctor. One of his headmasters said that he would never amount to anything. He never took an IQ tests, but some psychologists who think that everyone should have one, estimated that Einstein had an IQ of 160, which means that he could have joined MENSA, whatever that means. Einstein's genius is that he thought deeply about what most people take for granted. Richard Feynman (another Nobel Prize winner) actually took an IQ test in high school and score 125, which means that there is something wrong with IQ tests, or that they measure something else besides the skills that are important in physics.
Here is what was in the air in Einstein's world when he got his PhD. The null results of the Michaelson Morley Experiment shot down the idea of a preferred frame of reference and reinstated the idea of relativity, but modified from what Galileo proposed. Most of the physics community was left puzzled by the result, but Einstein, who had the habit of thinking deeper about the properties of space and time than most physicists, was able to solve the puzzle using simple algebra and subtle thinking that went against the common sense of his times. Einstein was the man to see through the complexity of the propagation of light, but this habit of deep thinking had marked him as a slow learner to his teachers.
Einstein was born in Germany of Jewish parents, at a time when that country was growing unstable and would later develop into a totalitarian state under Adolph Hitler. It was not the growing unrest in Germany that drove his family out of Germany. His father's business failed, so his parents moved to Italy, leaving young Einstein in Munich to finish his studies at the Luitpold Gymnasium. He did not complete his secondary education in Germany, but followed his parents to Italy, eventually settling in Switzerland (1895-96) where he completed his secondary eduction. After graduation, he enrolled in the Eidgenössische Polytechnische Schule.
In 1905 he had a miracle year, having received his PhD degree and published several landmark papers that would set the course of modern physics. The publication of the Theory of Special Relativity was one of his accomplishments during that miracle year. Most of this theory can be understood using simple algebra, but in this case the concepts behind the algebra are more challenging than the mathematics itself.
Nobel Prize
In 1921, Einstein received a Nobel Prize, not for Special Relativity, which was well tested, nor for General Relativity, which was proved by Arthur Eddington's experimental observation of the bending of light around the Sun during its eclipse. Instead, he was awarded the prize for "services to theoretical physics, and especially for his discovery of the law of the photoelectric effect". (See comments by Y. S. Kim about Einstein's Nobel Prize.) Although his work on the photoelectric effect is a major accomplishment, Einstein was best known for his work on Relativity. When he did receive the Nobel Prize, he was already internationally famous. It seems as if the prize committee thought that they had to give Einstein the Nobel Prize, but for some reason did not want to award it for his work on relativity. Still, they had to award him a Nobel Prize because he was an international celebrity for his work on Relativity. Had they not given the prize to Einstein, the prestige of the Nobel Prize would have suffered. So they looked around for something to pin it on, and found the work on the photoelectric effect. As it turned out, the photoelectric effect was a milestone in the road to developing the ideas of quantum mechanics. So that in retrospect, the explanation of photoelectric effect based on quantum mechanical considerations was an important paper in the history of physics.
The blogs on Relativity begin with the next one, Grokking Special Relativity.