Category:Albert Einstein

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Albert Einstein (1879 – 1955) is the person most popularly associated with the idea of relativity theory.

Born in Germany in the latter half of the Nineteenth Century, Einstein was an independent-minded student who earned the ire of his professors by not treating them what they considered to be adequate respect – when they proclaimed that a thing was true, instead of takign their word for it, Einstein would sometimes have the effrontery to ask how it was that we knew that such a thing was true. Disgraceful behaviour for a young scientist! His professors were also not amused by Einstein's apparent disdain for lab work, and his habit of not turning up to lectures to hear his professors speak.

Someone with such a disrespectful attitude clearly had no place in physics – Einstein, said his professor Hermann Minkowski, was a lazy dog who would never amount to anything. Although Einstein graduated, his professors wrote such bad references for him that he considered himself unemployable with respect to university work, and Einstein is supposed to have applied to every university in Europe for a position, and been rejected or ignored. At one point his father even resorted to writing begging letters on his behalf, pleading for his son to be considered for a position.

After a succession of tutoring and miscellaneous jobs, Einstein managed to get long-term employment at the Swiss Patent office as a patent examiner. He reputedly liked the work, and how it exposed his to a wide range of ideas that needed assessment, and used the stability and isolation to work on his own ideas. During this time he was separated from his wife and child, and living alone - this may have been partly because Swiss governmental departments took a dim view of children born out of wedlock and Einstein might have been less than completely honest about his domestic arrangements, but also partly because it allowed him to work without interruption.

1905, the Wonder Year: Special relativity

By 1905, Einstein had assembled enough ammunition to make an assault on the scientific community and claw his way into paid academia. He did this with a series of papers published in the German journal Annalen der Physik, which apparently had a policy that once an author had published in the journal once, further submissions tended to be nodded though unless there was something badly wrong with them. Having "opened the door" with his first accepted paper, Einstein fired a series of followup papers though the gap, and during 1905 published papers on the quantised nature of light and the photoelectric effect (a arguably the birth of quantum theory), a rederivation of the equations of Lorentzian aether theory (published in the same journal in 1904), which derived the relationships form more abstract principles with a set of relativistic arguments that later became known as special relativity, and a quick followup paper that showed that if the Lorentz-Einstein equations were correct, they led to the relationship E=mc^2.

This sudden body of published work got Einstein a full-time university position in 1909, at which point he quit his patent office job, and set to work developing further arguments and extensions of the 1905 work.

1911: Gravitational time dilation

In Einstein's 1911 "on the effect of gravitation on light", he argued that a gravitational gradient ought to shift the frequency and wavelength of any light crossing it. While the effect had been proposed before (and forgotten), by John Michell in 1783, Einstein went further and pointed out that the frequency-shifting of light-signals led to logical absurdities unless the rate of timeflow was physically different in different gravitational environments.

1911-1916

In 1916, Einstein published the finalised from of his theory of general relativity. GR was a curved-spacetime geometrical theory of gravitation, and while brilliant mathematicians had previously tried and failed to describe gravity in terms of curved-space geometry, Einstein's earlier trivial result that gravity also warped time coordinates meant that he had the secret to to solving the problem, which was to apply curvature in four dimensions rather than three, and obtain a description not of curved space, but curved spacetime.

Since he'd already published the critical piece of information in 1911, Einstein knew that he had competition many of whom were much better mathematicians than he was, and in an attempt to be the first to present a working theory, drove himself almost to the point of a breakdown. A major breakthrough was Einstein's realisation that a falling body feels "weightless" – if one dropped a small self-contained freefalling laboratory towards the Earth, then the earth's gravitational field would not obviously be detectable inside the lab. Einstein used this argument to say that gravitational physics needed to reduce over small free-falling regions to non-gravitational physics ("the happiest thought of my life"), declared that his general theory therefore should reduce to the existing physics of his special theory, and went on to complete a formulation.

1914-1918: World War One

One of the factors working in Einstein's favour was the outbreak of World War One (1914-1918). With many of his colleagues joining the military having their research diverted towards war work, Einstein (as a pacifist) was able to continue with his research with minimal interference or criticism from colleagues. Karl Schwarzchild (1873 – 1916), who might have been expected to provide Einstein with some competition had patriotically joined the army and died on the Eastern Front toward the end of the war.

Perihelion shift of Mercury

Einstein was aware that the highly-elliptical orbit of the planet Mercury constantly shifted its alignment, and that existing theory could only account for part of the effect. Keen to use the perihelion shift as a test of the theory, Einstein found that the correct amount of shift did in fact show up under the new general theory, and once all the remaining bugs were worked out of the mathematics, and the perihelion result was still present, Einstein declared the theory finished.

1919: Eddington

A new result of the 1916 theory was that light ought to be deflected by a gravitational field by roughly twice as much as had been predicted by Newtonian arguments. While Newton's system predicted light-bending analogous to curved space, and Einstein's 1911 arguments had led to essentially the same result as a result of "refractive index" arguments based on a variation on lightspeeds due to curved time, the combination of the two effects meant that according to the new general theory, light ought to be deflected by around twice as much by a gravitational field as had previously been predicted.

Arthur Eddington set out to mount an expedition to measure the apparent deflection of starlight during an eclipse, and reported agreement with the 1916 prediction. To a world deeply depressed by the carnage of WW1 and the loss of faith in existing political systems, the idea that a German and an Englishman had devised a new system of the world and demonstrated it correct was embraced by the public as a reason to be optimistic about the future, and Einstein became a celebrity.

With the rise to power of the Nazi party, Einstein left Germany for the United States, and took a position at the new Institute of Advanced Study, in Princeton.

1939: The A-Bomb letter

Einstein had originally argued that the idea of using nuclear power for anything useful was unworkable, since the only suitable element isotopes were vanishingy rare. Uranium 235 was a candidate, but uranium ore was only found in limited quantities, and more than 99% of that was in the form of U238. The discovery of large quantities of uranium ore in the Belgian Congo changed things, and when Einstein heard through his contacts with the Belgian Royal Family that Nazi Germany had taken control of the Congo and that its agents were interested in uranium, he deduced (correctly) that Germany was interested in exploring the idea of building a nuclear weapon, and wrote to President Franklin Roosevelt warning him of Germany's apparent intentions, and urging action by the United States.

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