We know the importance of the results obtained by Einstein in 1905 on the properties of matter. Albert Einstein was born on March 14, 1879 in Ulm, a medium-sized city in Württemberg in Germany.
In 1905, he published in the German journal "Annalen der Physik" four articles which revolutionized 20th century physics.
1) The first article, published on March 17, 1905, is revolutionary. Einstein titled it "On a heuristic point of view concerning the production and transformation of light".
Einstein exposes a revolutionary point of view on the corpuscular nature of the light, by the study of the photoelectric effect.
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2) On May 11, 1905, Albert Einstein published a second, rather subtle article on the Brownian motion described by the botanist Robert Brown in 1827. This article is titled "On the motion of suspended particles in a fluid at rest implied by the kinetic molecular theory of heat".
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3) On June 30, 1905, Albert Einstein published a third, even more revolutionary article entitled "On the electrodynamics of moving bodies".
In this article, Einstein attacks the postulate of an absolute space and an absolute time as defined by the mechanics of Isaac Newton (1643-1727). He calls into question the existence of the ether (inert interstellar medium which was to support the light). This article carries the princeps of the special theory of relativity (E=mc2), the most famous mathematical formula of physics.
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4) On September 27, 1905, still in the German magazine "Annalen der Physik", Einstein's fourth article appeared. It is called "Does the inertia of a body depend on its energy?".
This article leads to the mass-energy equivalence formula that is to say E=mc2. The special theory of relativity was born.
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NB: Heuristic, simply means that the research is not carried out rigorously, according to scientific laws, but indicates a search path towards which there is something to be found.
NB: Brownian motion was first described in 1827. Robert Brown notices in nature that stones contain water, in which there are grains of pollen. These pollen grains move while they have been locked up for millions of years.
How is it that these pollen grains are moving?
This is Brownian motion. Einstein explains this Brownian motion by the molecular and atomic hypothesis and calculates the size of molecules.