Editing Albert Einstein (section)

=== Putting general relativity to the test (1919)===
[[File:19191125 A New Physics Based on Einstein - The New York Times.png|thumb|right| ''[[The New York Times]]'' reported confirmation of the bending of light by gravitation after observations (made in [[Príncipe]] and [[Sobral, Ceará|Sobral]]) of the 29 May 1919 eclipse were presented to a joint meeting in London of the [[Royal Society]] and the [[Royal Astronomical Society]] on 6 November 1919.<ref name="NYTimes_19191125"/>]]
In 1907, Einstein reached a milestone on his long journey from his special theory of relativity to a new idea of gravitation with the formulation of his [[equivalence principle]], which asserts that an observer in a box falling freely in a gravitational field would be unable to find any evidence that the field exists. In 1911, he used the principle to estimate the amount by which a ray of light from a distant star would be [[Gravitational lens|bent]] by the gravitational pull of the Sun as it passed close to the Sun's [[photosphere]] (that is, the Sun's apparent surface). He reworked his calculation in 1913, having now found a way to model gravitation with the [[Riemann curvature tensor]] of a non-Euclidean four-dimensional [[spacetime]]. By the fall of 1915, his reimagining of the mathematics of gravitation in terms of Riemannian geometry was complete, and he applied his new theory not just to the behavior of the Sun as a gravitational lens but also to another astronomical phenomenon, the [[precession of the perihelion of Mercury]] (a slow drift in the point in Mercury's elliptical orbit at which it approaches the Sun most closely).<ref name=dh/><ref>{{cite book |last1=Weinberg |first1=Steven |title=Gravitation and Cosmology: Principles and applications of the general theory of relativity |date=1972 |publisher=John Wiley & Sons, Inc. |isbn=9788126517558 |pages=19–20}}</ref> A [[Solar eclipse of May 29, 1919|total eclipse of the Sun that took place on 29 May 1919]] provided an opportunity to put his theory of gravitational lensing to the test, and observations performed by Sir [[Arthur Eddington]] yielded results that were consistent with his calculations. Eddington's work was reported at length in newspapers around the world. On 7 November 1919, for example, the leading British newspaper, ''[[The Times]]'', printed a banner headline that read: {{qi|Revolution in Science{{nbs}}– New Theory of the Universe{{nbs}}– Newtonian Ideas Overthrown}}.<ref name="Eddington"/>