Albert Einstein (March 14, 1879 - April 18, 1955) was a physicist and mathematician who proposed the theory of relativity, the quantum theory of light, and a proof of the atom. He made major contributions to the development of quantum mechanics, statistical mechanics and cosmology, and is generally regarded as the most important physicist of the 20th century. He was awarded the 1921 Nobel Prize for Physics for his explanation of the photoelectric effect "and other contributions"; however, the announcement of the award was not made until a year later, in 1922. Abram Joffe, in his biography, argues that Einstein was assisted by his wife Mileva Maric, who was also a physicist.
Born at Ulm in Württemberg, Germany, Einstein grew up in Munich and later in Italy and received his higher education in Switzerland. He renounced his German citizenship and was accepted as a Swiss citizen in 1901. He was an examiner at the Swiss Patent Office from 1902-1905. He obtained his doctorate in 1905. That same year, he wrote four articles that laid the foundation for modern physics.
The first article in this remarkable year is remembered as his study of Brownian motion. It established empirical evidence for the reality of atoms. Before this paper, atoms were recognized as a useful concept, but physicists and chemists hotly debated the question of whether atoms were real things. Einstein's statistical discussion of atomic behavior gave experimentalists a way to count atoms by looking through an ordinary microscope. Wilhelm Ostwald, one of the leaders of the anti-atom school, later told Arnold Sommerfeld that he had been converted to a belief in atoms by Einstein's complete explanation of Brownian motion.
The second paper of 1905 proposed the idea of "light quanta" (now called photons) and showed how they could be used to explain such phenomena as the photoelectric effect. The theory of light quanta contradicted the wave theory of light that followed naturally from James Clerk Maxwell's equations for electromagnetic behavior. By simultaneously incorporating wave-like and particle-like properties for photons, it demonstrated wave-particle duality. Even after experiments showed that Einstein's equations for the photoelectric effect were accurate, his explanation was not universally accepted. In 1922, when he was awarded the Nobel Prize, and his work on photoelectricity was mentioned by name, most physicists thought that, while the equation was correct, light quanta were impossible. The complete picture did not emerge until the maturity of quantum mechanics.
1905's third paper introduced the special theory of relativity, an accurate theory of time, distance, mass and energy (which is consistent with electromagnetism, but omits the force of gravity). Special relativity solved the puzzle that had been apparent since the Michelson-Morley experiment, which had shown that light waves could not be travelling through any medium (other known waves travelled through media - such as water or air). The speed of light was thus fixed, and not relative to the movement of the observer. This is impossible under Newtonian classical mechanics.
Some of the paper's core mathematical ideas -- the Lorentz transforms -- had been introduced a year earlier by the Dutch physicist Hendrik Lorentz, but Einstein showed how to understand these mathematical oddities. His explanation arose from two axioms: one was Galileo's old idea that the laws of nature should be the same for all observers that move with constant speed relative to each other; and, two, that the speed of light is the same for every observer. Special relativity has several striking consequences because the absolute concepts of time and size are rejected. The theory came to be called "special theory of relativity" to distinguish it from his later theory of general relativity, which considers all observers to be equivalent.
A fourth paper published later that same year showed one further deduction from relativity's axioms. That deduction was the famous equation that rest energy (E) equals mass (m) times the speed of light (c) squared: E = mc2. Einstein considered this equation to be of paramount importance because it showed that matter and energy are profoundly linked. The idea later proved invaluable for understanding how the Big Bang, which was a pure burst of energy, could lead to the precipitation of a universe filled with matter (it turns out that the energy required to create the matter is exactly offset by the negative potential energy of the universe's gravitational well).
The equation is often cited as an explanation of how atomic weapons produce such phenomenal amounts of energy. Although this is literally true (the mass of the residue from a nuclear blast is smaller than the mass of the original weapon; the difference has been converted to energy, as per the formula), it is also misleading, because the theory of relativity is not the key to the physics of fission or fusion.
In 1914, just before the start of World War I, Einstein settled in Berlin. His pacifism and Jewish origins outraged German nationalists. After he became world-famous (on November 7, 1919, when The Times reported the success of his gravitational theory) nationalist hatred of him grew even more ferocious.
From 1914 to 1933 he served as director of Kaiser Wilhelm Institute for Physics in Berlin, and it was during this time he received his Nobel Prize.
In November 1915, Einstein presented a series of lectures before the Prussian Academy of Sciences in which he described his theory of general relativity. The final lecture climaxed with his introduction of an equation that replaced Newton's law of gravity. This theory considers all observers to be equivalent, not only those moving at a uniform speed. In general relativity, gravity is no longer a force (as it was in Newton's law of gravity) but is a consequence of the curvature of space-time. The theory provided the foundation for the study of cosmology and gave scientists the tools for understanding many features of the universe that were not discovered until well after Einstein's death.
Einstein spent the last forty years of his life trying to unify gravity and electromagnetism giving a new subtle understand of quantum mechanics. He was looking for a classical unification of gravity and electromagnetism.
Einstein's relationship with quantum physics is quite remarkable. He was the first, even before Max Planck, the discoverer of the quantum, to say that quantum theory was revolutionary. His idea of light quanta was a landmark break with the classical understanding of physics. In 1909, Einstein presented his first paper to a gathering of physicists and told them that they must find some way to understand waves and particles together.
In the early 1920s, Einstein was the lead figure in a famous weekly physics colloquium at the University of Berlin.
However, in the mid-1920s, as the original quantum theory was replaced with a new quantum mechanics, Einstein balked at the Copenhagen interpretation of the new equations because it settled for a probabilistic, non-visualizable account of physical behavior. Einstein agreed that the theory was the best available, but he looked for an explanation that would be more "complete," i.e., deterministic. His belief that physics described the laws that govern "real things" had led to his successes with atoms, photons, and gravity. He was unwilling to abandon that faith.
Einstein's famous remark, "Quantum mechanics is certainly imposing. But an inner voice tells me it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the Old One. I, at any rate, am convinced that he does not throw dice," appeared in a 1926 letter to Max Born. It was not a rejection of probabilistic theories per se. Einstein had used statistical analysis in his work on Brownian motion and photoelectricity. In papers published before the miraculous year of 1905 he had even discovered Gibbs ensembles on his own. But he did not believe that, at bottom, physical reality behaves randomly.
In 1924, Einstein received a short paper from a young Indian physicist named Satyendra Nath Bose, describing light as a gas of photons, and asking for Einstein's assistance in publication. Einstein realised that the same statistics could be applied to atoms, and published an article in German (then the lingua franca of physics) which described Bose's model and explained its implications. Bose Einstein statistics are now known to describe any gas of indistinguishable particles (bosons). Einstein also assisted Erwin Schrödinger in the development of the Quantum Boltzmann distribution, a mixed classical and quantum mechanical gas model -- although he realised that this was less significant that the Bose Einstein model, and declined to have his name included on the paper.
After Adolf Hitler came to power in 1933, Einstein was accused by the National Socialist regime of creating a "Jewish physics". Nazi physicists (notably including the Nobel laureate Johannes Stark) attempted to discredit his theories. Einstein fled to the United States and accepted a position at the Institute of Advanced Study in Princeton, New Jersey. He became an American citizen in 1940. He spent his last 20 years in an increasingly isolated and ultimately unsuccessful attempt at constructing a theory that would unify General Relativity and quantum mechanics.
He died in Princeton.
Einstein married his first wife, Mileva Maric on January 6, 1903. Her role in his early years is subject of much controversy. She was about 4 years older than him. They had three children. They were divorced on February 14, 1919. Einstein married his cousin Elsa Loewenthal (née Einstein: Loewenthal was the surname of her first husband, Max) on June 2, 1919. Elsa was Albert's first cousin (maternally) and his second cousin (paternally) and she was 3 years older than Albert. There were no children from this marriage.
The fate of Albert and Mileva's first child, a daughter, born prior to their marriage, is unknown: some believe she died in infancy and some believe she was given out for adoption. The other two children were boys: one was institutionalized for schizophrenia and died in an asylum. The other moved to California and became a university professor, and had little interaction with his father.
Einstein considered himself a pacifist  and humanitarian . Einstein's views on other issues, including socialism, McCarthyism and racism, were controversial. (Einstein on socialism)
The American FBI kept a 1,427 page file on his activities and recommended that he be barred from immigrating to the United States under the Alien Exclusion Act, alleging that Einstein "believes in, advises, advocates, or teaches a doctrine which, in a legal sense, as held by the courts in other cases, 'would allow anarchy to stalk in unmolested' and result in 'government in name only'," among other charges.
Einstein initially favored construction of the atomic bomb, in order to ensure that Hitler did not do so first, and he even sent a letter to President Roosevelt (dated August 2, 1939, before WW-II broke out) encouraging him to initiate a programme to create a nuclear weapon. But after the war he lobbied for nuclear disarmament and a world government.
He was offered the opportunity to become the first President of Israel but declined. His religious views were close to the pantheism of Baruch Spinoza: he believed that God revealed himself in the holy harmony of the laws of nature and he rejected a personal God able to interact with humans. He once said that among the major religions, he preferred Buddhism.
Albert Einstein has become the subject of a number of novels, films and plays including Nicolas Roeg's film, Insignificance and Alan Lightman's novel, Einstein's Dreams. Einstein was even the subject of Philip Glass's groundbreaking 1976 opera Einstein on the Beach.
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