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Einstein also recognized another element of the definition of an exact solution: it should be a Lorentzian manifold (meeting additional criteria), i.e. a smooth manifold. But in working with general relativity, it turns out to be very useful to admit solutions which are not everywhere smooth; examples include many solutions created by matching ...
Einstein himself considered the introduction of the cosmological constant in his 1917 paper founding cosmology as a "blunder". [3] The theory of general relativity predicted an expanding or contracting universe, but Einstein wanted a static universe which is an unchanging three-dimensional sphere, like the surface of a three-dimensional ball in four dimensions.
The Einstein field equations are nonlinear and considered difficult to solve. Einstein used approximation methods in working out initial predictions of the theory. But in 1916, the astrophysicist Karl Schwarzschild found the first non-trivial exact solution to the Einstein field equations, the Schwarzschild metric. This solution laid the ...
Such a shape is called an einstein, a word play on ein Stein, German for "one stone". [ 2 ] Several variants of the problem, depending on the particular definitions of nonperiodicity and the specifications of what sets may qualify as tiles and what types of matching rules are permitted, were solved beginning in the 1990s.
In physics, the special theory of relativity, or special relativity for short, is a scientific theory of the relationship between space and time.In Albert Einstein's 1905 paper, On the Electrodynamics of Moving Bodies, the theory is presented as being based on just two postulates: [p 1] [1] [2]
Albert Einstein's discovery of the gravitational field equations of general relativity and David Hilbert's almost simultaneous derivation of the theory using an elegant variational principle, [B 1]: 170 during a period when the two corresponded frequently, has led to numerous historical analyses of their interaction.
Only Einstein's theory proved to be consistent with experiments and observations. To understand the theory's basic ideas, it is instructive to follow Einstein's thinking between 1907 and 1915, from his simple thought experiment involving an observer in free fall to his fully geometric theory of gravity. [1]
Einstein, Albert (1956) [1922]. The Meaning of Relativity (5 ed.). Princeton University Press. The Meaning of Relativity Albert Einstein: Four lectures delivered at Princeton University, May 1921; How I created the theory of relativity Albert Einstein, 14 December 1922; Physics Today August 1982; Relativity Sidney Perkowitz Encyclopædia Britannica