Relativity: The Special and the General Theory
Albert Einstein completed a fifty-page account of his theories in March 1916. He published the German version titled Über die spezielle und die allgemeine Relativitätstheorie, gemeinverständlich later that same year. Abraham Pais suggests Hendrik Lorentz may have influenced Einstein to write this popularization. The book became widely known after results from an eclipse expedition caused a major stir in December 1916. An English translation appeared in 1920 and has been reprinted many times since then. Princeton University Press issued a 100th Anniversary Edition in 2015. This edition was also released as an e-book in 2019.
Einstein introduced Galilean invariance by describing two coordinate systems K and K′ moving uniformly relative to one another. He argued that mechanical laws hold good exactly as they do with respect to either system. Light propagation takes place in straight lines with a velocity c equal to 300,000 km per second. Dutch astronomer De Sitter showed that light velocity cannot depend on the motion of the body emitting it. A thought experiment involving a railway carriage and embankment demonstrated that observers measure the same speed of light regardless of their frame. Lightning flashes at points A and B appear simultaneous to an observer on the embankment but not to one on the train. Hermann Minkowski formulated the concept of spacetime which Einstein incorporated into his work. Time dilation emerged as a nonintuitive consequence of the Lorentz transformation equations.
A piece of lead and a piece of wood fall in exactly the same manner in a gravitational field when starting from rest. Einstein used this observation to argue that gravitational mass equals inertial mass for all bodies. He asked readers to imagine an occupant inside a chest accelerating freely through empty space. That person would conclude they were at rest in a gravitational field because released objects approach the floor with accelerated relative motion. An observer on a rotating disk required non-Euclidean geometry to describe gravity accurately. Newton's theory could not account for the precession of Mercury's perihelion. Urbain Le Verrier predicted Neptune based on deviations from Newton but failed to explain the 43 seconds of arc per century shift. General relativity predicts the correct value strictly in agreement with observation.
The theory raises the possibility that the Universe is finite but unbounded. Alexander Friedmann showed in 1922 that the theory demands an expansion of space. Hubble later investigated extra-galactic nebulae known as milky ways. Spectral lines emitted by these nebulae showed a red shift increasing regularly with distance. This can be interpreted as an expansive motion of stars in the large sense. The discovery confirmed what Friedman had derived from the field equations of gravitation. Einstein applied general relativity directly to cosmology to explore the structure of the universe as a whole.
Arthur Eddington confirmed light should curve towards a massive body during his 1919 eclipse expedition. Walter Sydney Adams verified in 1925 that light from a massive star shifts to the red. The theory predicts the correct value of 43 arc-seconds per century for Mercury's orbital precession. These three confirmations provided strong evidence for the validity of general relativity. The predictions matched observations with strict accuracy across different astronomical phenomena. Scientists used these results to validate the mathematical framework Einstein had developed over many years.
A review in Nature called it an excellent translation and hastened to know the whole truth. Walther Rathenau wrote a letter stating he was immersed in Einstein's ideas for weeks. He noted how radical rearrangement of ideas passed through simple means using classical architectonics. Robert W. Lawson described the work as unique for giving insight into thought processes of one of the greatest minds of the 20th century. Martin Rees, Astronomer Royal, said the book displays style and clarity accessible to wide readership. The text remains an important historical document while maintaining scientific rigor for non-specialists.
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Common questions
When did Albert Einstein complete the manuscript for Relativity: The Special and the General Theory?
Albert Einstein completed a fifty-page account of his theories in March 1916. He published the German version titled Über die spezielle und die allgemeine Relativitätstheorie, gemeinverständlich later that same year.
What specific astronomical observation confirmed general relativity during an eclipse expedition in December 1916?
Results from an eclipse expedition caused a major stir in December 1916 after Arthur Eddington confirmed light should curve towards a massive body during his 1919 eclipse expedition. These results provided strong evidence for the validity of general relativity by matching observations with strict accuracy across different astronomical phenomena.
How does Albert Einstein explain the equivalence between gravitational mass and inertial mass in his book?
Einstein used the observation that a piece of lead and a piece of wood fall in exactly the same manner in a gravitational field when starting from rest to argue that gravitational mass equals inertial mass for all bodies. He asked readers to imagine an occupant inside a chest accelerating freely through empty space who would conclude they were at rest in a gravitational field because released objects approach the floor with accelerated relative motion.
Which scientist showed in 1922 that Albert Einstein's theory demands an expansion of space?
Alexander Friedmann showed in 1922 that the theory demands an expansion of space. Hubble later investigated extra-galactic nebulae known as milky ways where spectral lines emitted by these nebulae showed a red shift increasing regularly with distance, confirming what Friedman had derived from the field equations of gravitation.
What value did Albert Einstein predict for Mercury's orbital precession per century?
The theory predicts the correct value of 43 arc-seconds per century for Mercury's orbital precession. Newton's theory could not account for the precession of Mercury's perihelion but general relativity predicts the correct value strictly in agreement with observation.