Theory of relativity
The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively.^{[1]} Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to other forces of nature.^{[2]} It applies to the cosmological and astrophysical realm, including astronomy.^{[3]}
The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200yearold theory of mechanics created primarily by Isaac Newton.^{[3]}^{[4]}^{[5]} It introduced concepts including 4dimensional spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction. In the field of physics, relativity improved the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.^{[3]}^{[4]}^{[5]}
Development and acceptance
General relativity 


Albert Einstein published the theory of special relativity in 1905, building on many theoretical results and empirical findings obtained by Albert A. Michelson, Hendrik Lorentz, Henri Poincaré and others. Max Planck, Hermann Minkowski and others did subsequent work.
Einstein developed general relativity between 1907 and 1915, with contributions by many others after 1915. The final form of general relativity was published in 1916.^{[3]}
The term "theory of relativity" was based on the expression "relative theory" (German: Relativtheorie) used in 1906 by Planck, who emphasized how the theory uses the principle of relativity. In the discussion section of the same paper, Alfred Bucherer used for the first time the expression "theory of relativity" (German: Relativitätstheorie).^{[6]}^{[7]}
By the 1920s, the physics community understood and accepted special relativity.^{[8]} It rapidly became a significant and necessary tool for theorists and experimentalists in the new fields of atomic physics, nuclear physics, and quantum mechanics.
By comparison, general relativity did not appear to be as useful, beyond making minor corrections to predictions of Newtonian gravitation theory.^{[3]} It seemed to offer little potential for experimental test, as most of its assertions were on an astronomical scale. Its mathematics seemed difficult and fully understandable only by a small number of people. Around 1960, general relativity became central to physics and astronomy. New mathematical techniques to apply to general relativity streamlined calculations and made its concepts more easily visualized. As astronomical phenomena were discovered, such as quasars (1963), the 3kelvin microwave background radiation (1965), pulsars (1967), and the first black hole candidates (1981),^{[3]} the theory explained their attributes, and measurement of them further confirmed the theory.
Special relativity
Special relativity is a theory of the structure of spacetime. It was introduced in Einstein's 1905 paper "On the Electrodynamics of Moving Bodies" (for the contributions of many other physicists see History of special relativity). Special relativity is based on two postulates which are contradictory in classical mechanics:
 The laws of physics are the same for all observers in any inertial frame of reference relative to one another (principle of relativity).
 The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source.
The resultant theory copes with experiment better than classical mechanics. For instance, postulate 2 explains the results of the Michelson–Morley experiment. Moreover, the theory has many surprising and counterintuitive consequences. Some of these are:
 Relativity of simultaneity: Two events, simultaneous for one observer, may not be simultaneous for another observer if the observers are in relative motion.
 Time dilation: Moving clocks are measured to tick more slowly than an observer's "stationary" clock.
 Length contraction: Objects are measured to be shortened in the direction that they are moving with respect to the observer.
 Maximum speed is finite: No physical object, message or field line can travel faster than the speed of light in a vacuum.
 The effect of gravity can only travel through space at the speed of light, not faster or instantaneously.
 Mass–energy equivalence: E = mc^{2}, energy and mass are equivalent and transmutable.
 Relativistic mass, idea used by some researchers.^{[9]}
The defining feature of special relativity is the replacement of the Galilean transformations of classical mechanics by the Lorentz transformations. (See Maxwell's equations of electromagnetism.)
General relativity
General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field (for example, when standing on the surface of the Earth) are physically identical. The upshot of this is that free fall is inertial motion: an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as is the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects cannot accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first proposed that spacetime is curved. In 1915, he devised the Einstein field equations which relate the curvature of spacetime with the mass, energy, and any momentum within it.
Some of the consequences of general relativity are:
 Gravitational time dilation: Clocks run slower in deeper gravitational wells.^{[10]}
 Precession: Orbits precess in a way unexpected in Newton's theory of gravity. (This has been observed in the orbit of Mercury and in binary pulsars).
 Light deflection: Rays of light bend in the presence of a gravitational field.
 Framedragging: Rotating masses "drag along" the spacetime around them.
 Metric expansion of space: The universe is expanding, and the far parts of it are moving away from us faster than the speed of light.
Technically, general relativity is a theory of gravitation whose defining feature is its use of the Einstein field equations. The solutions of the field equations are metric tensors which define the topology of the spacetime and how objects move inertially.
Experimental evidence
Einstein stated that the theory of relativity belongs to a class of "principletheories". As such, it employs an analytic method, which means that the elements of this theory are not based on hypothesis but on empirical discovery. By observing natural processes, we understand their general characteristics, devise mathematical models to describe what we observed, and by analytical means we deduce the necessary conditions that have to be satisfied. Measurement of separate events must satisfy these conditions and match the theory's conclusions.^{[2]}
Tests of special relativity
Relativity is a falsifiable theory: It makes predictions that can be tested by experiment. In the case of special relativity, these include the principle of relativity, the constancy of the speed of light, and time dilation.^{[11]} The predictions of special relativity have been confirmed in numerous tests since Einstein published his paper in 1905, but three experiments conducted between 1881 and 1938 were critical to its validation. These are the Michelson–Morley experiment, the Kennedy–Thorndike experiment, and the Ives–Stilwell experiment. Einstein derived the Lorentz transformations from first principles in 1905, but these three experiments allow the transformations to be induced from experimental evidence.
Maxwell's equations—the foundation of classical electromagnetism—describe light as a wave that moves with a characteristic velocity. The modern view is that light needs no medium of transmission, but Maxwell and his contemporaries were convinced that light waves were propagated in a medium, analogous to sound propagating in air, and ripples propagating on the surface of a pond. This hypothetical medium was called the luminiferous aether, at rest relative to the "fixed stars" and through which the Earth moves. Fresnel's partial ether dragging hypothesis ruled out the measurement of firstorder (v/c) effects, and although observations of secondorder effects (v^{2}/c^{2}) were possible in principle, Maxwell thought they were too small to be detected with thencurrent technology.^{[12]}^{[13]}
The Michelson–Morley experiment was designed to detect secondorder effects of the "aether wind"—the motion of the aether relative to the earth. Michelson designed an instrument called the Michelson interferometer to accomplish this. The apparatus was sufficiently accurate to detect the expected effects, but he obtained a null result when the first experiment was conducted in 1881,^{[14]} and again in 1887.^{[15]} Although the failure to detect an aether wind was a disappointment, the results were accepted by the scientific community.^{[13]} In an attempt to salvage the aether paradigm, FitzGerald and Lorentz independently created an ad hoc hypothesis in which the length of material bodies changes according to their motion through the aether.^{[16]} This was the origin of FitzGerald–Lorentz contraction, and their hypothesis had no theoretical basis. The interpretation of the null result of the Michelson–Morley experiment is that the roundtrip travel time for light is isotropic (independent of direction), but the result alone is not enough to discount the theory of the aether or validate the predictions of special relativity.^{[17]}^{[18]}
While the Michelson–Morley experiment showed that the velocity of light is isotropic, it said nothing about how the magnitude of the velocity changed (if at all) in different inertial frames. The Kennedy–Thorndike experiment was designed to do that, and was first performed in 1932 by Roy Kennedy and Edward Thorndike.^{[19]} They obtained a null result, and concluded that "there is no effect ... unless the velocity of the solar system in space is no more than about half that of the earth in its orbit".^{[18]}^{[20]} That possibility was thought to be too coincidental to provide an acceptable explanation, so from the null result of their experiment it was concluded that the roundtrip time for light is the same in all inertial reference frames.^{[17]}^{[18]}
The Ives–Stilwell experiment was carried out by Herbert Ives and G.R. Stilwell first in 1938^{[21]} and with better accuracy in 1941.^{[22]} It was designed to test the transverse Doppler effect – the redshift of light from a moving source in a direction perpendicular to its velocity—which had been predicted by Einstein in 1905. The strategy was to compare observed Doppler shifts with what was predicted by classical theory, and look for a Lorentz factor correction. Such a correction was observed, from which was concluded that the frequency of a moving atomic clock is altered according to special relativity.^{[17]}^{[18]}
Those classic experiments have been repeated many times with increased precision. Other experiments include, for instance, relativistic energy and momentum increase at high velocities, experimental testing of time dilation, and modern searches for Lorentz violations.
Tests of general relativity
General relativity has also been confirmed many times, the classic experiments being the perihelion precession of Mercury's orbit, the deflection of light by the Sun, and the gravitational redshift of light. Other tests confirmed the equivalence principle and frame dragging.
Modern applications
Far from being simply of theoretical interest, relativistic effects are important practical engineering concerns. Satellitebased measurement needs to take into account relativistic effects, as each satellite is in motion relative to an Earthbound user and is thus in a different frame of reference under the theory of relativity. Global positioning systems such as GPS, GLONASS, and Galileo, must account for all of the relativistic effects, such as the consequences of Earth's gravitational field, in order to work with precision.^{[23]} This is also the case in the highprecision measurement of time.^{[24]} Instruments ranging from electron microscopes to particle accelerators would not work if relativistic considerations were omitted.^{[25]}
Asymptotic symmetries
The spacetime symmetry group for Special Relativity is the Poincaré group, which is a tendimensional group of three Lorentz boosts, three rotations, and four spacetime translations. It is logical to ask what symmetries if any might apply in General Relativity. A tractable case may be to consider the symmetries of spacetime as seen by observers located far away from all sources of the gravitational field. The naive expectation for asymptotically flat spacetime symmetries might be simply to extend and reproduce the symmetries of flat spacetime of special relativity, viz., the Poincaré group.
In 1962, Hermann Bondi, M. G. van der Burg, A. W. Metzner^{[26]} and Rainer K. Sachs^{[27]} addressed this asymptotic symmetry problem in order to investigate the flow of energy at infinity due to propagating gravitational waves. Their first step was to decide on some physically sensible boundary conditions to place on the gravitational field at lightlike infinity to characterize what it means to say a metric is asymptotically flat, making no a priori assumptions about the nature of the asymptotic symmetry group — not even the assumption that such a group exists. Then after designing what they considered to be the most sensible boundary conditions, they investigated the nature of the resulting asymptotic symmetry transformations that leave invariant the form of the boundary conditions appropriate for asymptotically flat gravitational fields. What they found was that the asymptotic symmetry transformations actually do form a group and the structure of this group does not depend on the particular gravitational field that happens to be present. This means that, as expected, one can separate the kinematics of spacetime from the dynamics of the gravitational field at least at spatial infinity. The puzzling surprise in 1962 was their discovery of a rich infinitedimensional group (the socalled BMS group) as the asymptotic symmetry group, instead of the finitedimensional Poincaré group, which is a subgroup of the BMS group. Not only are the Lorentz transformations asymptotic symmetry transformations, there are also additional transformations that are not Lorentz transformations but are asymptotic symmetry transformations. In fact, they found an additional infinity of transformation generators known as supertranslations. This implies the conclusion that General Relativity does not reduce to special relativity in the case of weak fields at long distances.^{[28]}^{: 35 }
See also
 Doubly special relativity
 Galilean invariance
 General relativity references
 Special relativity references
References
 ^ Einstein A. (1916), (Translation 1920), New York: H. Holt and Company
 ^ ^{a} ^{b} Einstein, Albert (November 28, 1919). . The Times.
 ^ ^{a} ^{b} ^{c} ^{d} ^{e} ^{f} Will, Clifford M (2010). "Relativity". Grolier Multimedia Encyclopedia. Archived from the original on 20200521. Retrieved 20100801.
 ^ ^{a} ^{b} Will, Clifford M (2010). "SpaceTime Continuum". Grolier Multimedia Encyclopedia. Retrieved 20100801.
 ^ ^{a} ^{b} Will, Clifford M (2010). "Fitzgerald–Lorentz contraction". Grolier Multimedia Encyclopedia. Retrieved 20100801.
 ^ Planck, Max (1906), , Physikalische Zeitschrift, 7: 753–761
 ^ Miller, Arthur I. (1981), Albert Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905–1911), Reading: Addison–Wesley, ISBN 9780201046793
 ^ Hey, Anthony J.G.; Walters, Patrick (2003). The New Quantum Universe (illustrated, revised ed.). Cambridge University Press. p. 227. Bibcode:2003nqu..book.....H. ISBN 9780521564571.
 ^ Greene, Brian. "The Theory of Relativity, Then and Now". Retrieved 20150926.
 ^ Feynman, Richard Phillips; Morínigo, Fernando B.; Wagner, William; Pines, David; Hatfield, Brian (2002). Feynman Lectures on Gravitation. West view Press. p. 68. ISBN 9780813340388., Lecture 5
 ^ Roberts, T; Schleif, S; Dlugosz, JM, eds. (2007). "What is the experimental basis of Special Relativity?". Usenet Physics FAQ. University of California, Riverside. Retrieved 20101031.
 ^ Maxwell, James Clerk (1880), Bibcode:1880Natur..21S.314., doi:10.1038/021314c0 , Nature, 21 (535): 314–315,
 ^ ^{a} ^{b} Pais, Abraham (1982). "Subtle is the Lord ...": The Science and the Life of Albert Einstein (1st ed.). Oxford: Oxford Univ. Press. pp. 111–113. ISBN 9780192806727.
 ^ Michelson, Albert A. (1881). Bibcode:1881AmJS...22..120M. doi:10.2475/ajs.s322.128.120. S2CID 130423116. . American Journal of Science. 22 (128): 120–129.
 ^ Michelson, Albert A. & Morley, Edward W. (1887). . American Journal of Science. 34 (203): 333–345. Bibcode:1887AmJS...34..333M. doi:10.2475/ajs.s334.203.333. S2CID 124333204.
{{cite journal}}
: CS1 maint: multiple names: authors list (link)  ^ Pais, Abraham (1982). "Subtle is the Lord ...": The Science and the Life of Albert Einstein (1st ed.). Oxford: Oxford Univ. Press. p. 122. ISBN 9780192806727.
 ^ ^{a} ^{b} ^{c} Robertson, H.P. (July 1949). "Postulate versus Observation in the Special Theory of Relativity" (PDF). Reviews of Modern Physics. 21 (3): 378–382. Bibcode:1949RvMP...21..378R. doi:10.1103/RevModPhys.21.378.
 ^ ^{a} ^{b} ^{c} ^{d} Taylor, Edwin F.; John Archibald Wheeler (1992). Spacetime physics: Introduction to Special Relativity (2nd ed.). New York: W.H. Freeman. pp. 84–88. ISBN 9780716723271.
 ^ Kennedy, R.J.; Thorndike, E.M. (1932). "Experimental Establishment of the Relativity of Time" (PDF). Physical Review. 42 (3): 400–418. Bibcode:1932PhRv...42..400K. doi:10.1103/PhysRev.42.400. S2CID 121519138. Archived from the original (PDF) on 20200706.
 ^ Robertson, H.P. (July 1949). "Postulate versus Observation in the Special Theory of Relativity" (PDF). Reviews of Modern Physics. 21 (3): 381. Bibcode:1949RvMP...21..378R. doi:10.1103/revmodphys.21.378.
 ^ Ives, H.E.; Stilwell, G.R. (1938). "An experimental study of the rate of a moving atomic clock". Journal of the Optical Society of America. 28 (7): 215. Bibcode:1938JOSA...28..215I. doi:10.1364/JOSA.28.000215.
 ^ Ives, H.E.; Stilwell, G.R. (1941). "An experimental study of the rate of a moving atomic clock. II". Journal of the Optical Society of America. 31 (5): 369. Bibcode:1941JOSA...31..369I. doi:10.1364/JOSA.31.000369.
 ^ Ashby, N. Relativity in the Global Positioning System. Living Rev. Relativ. 6, 1 (2003). https://doi.org/10.12942/lrr20031"Archived copy" (PDF). Archived from the original (PDF) on 20151105. Retrieved 20151209.
{{cite web}}
: CS1 maint: archived copy as title (link)  ^ Francis, S.; B. Ramsey; S. Stein; Leitner, J.; Moreau, J.M.; Burns, R.; Nelson, R.A.; Bartholomew, T.R.; Gifford, A. (2002). "Timekeeping and Time Dissemination in a Distributed SpaceBased Clock Ensemble" (PDF). Proceedings 34th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting: 201–214. Archived from the original (PDF) on 17 February 2013. Retrieved 14 April 2013.
 ^ Hey, Tony; Hey, Anthony J. G.; Walters, Patrick (1997). Einstein's Mirror (illustrated ed.). Cambridge University Press. p. x (preface). ISBN 9780521435321.
 ^ Bondi, H.; Van der Burg, M.G.J.; Metzner, A. (1962). "Gravitational waves in general relativity: VII. Waves from axisymmetric isolated systems". Proceedings of the Royal Society of London A. A269 (1336): 21–52. Bibcode:1962RSPSA.269...21B. doi:10.1098/rspa.1962.0161. S2CID 120125096.
 ^ Sachs, R. (1962). "Asymptotic symmetries in gravitational theory". Physical Review. 128 (6): 2851–2864. Bibcode:1962PhRv..128.2851S. doi:10.1103/PhysRev.128.2851.
 ^ Strominger, Andrew (2017). "Lectures on the Infrared Structure of Gravity and Gauge Theory". arXiv:1703.05448.
...redacted transcript of a course given by the author at Harvard in spring semester 2016. It contains a pedagogical overview of recent developments connecting the subjects of soft theorems, the memory effect and asymptotic symmetries in fourdimensional QED, nonabelian gauge theory and gravity with applications to black holes. To be published Princeton University Press, 158 pages.
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Further reading
 Einstein, Albert (2005). Relativity: The Special and General Theory. Translated by Robert W. Lawson (The masterpiece science ed.). New York: Pi Press. ISBN 9780131862616.
 Einstein, Albert (1920). Relativity: The Special and General Theory (PDF). Henry Holt and Company.
 Einstein, Albert; trans. Schilpp; Paul Arthur (1979). Albert Einstein, Autobiographical Notes (A Centennial ed.). La Salle, IL: Open Court Publishing Co. ISBN 9780875483528.
 Einstein, Albert (2009). Einstein's Essays in Science. Translated by Alan Harris (Dover ed.). Mineola, NY: Dover Publications. ISBN 9780486470115.
 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, December 14, 1922; Physics Today August 1982
 Relativity Sidney Perkowitz Encyclopædia Britannica
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This is a mosaic image, one of the largest ever taken by NASA's Hubble Space Telescope, of the Crab Nebula, a sixlightyearwide expanding remnant of a star's supernova explosion. Japanese and Chinese astronomers recorded this violent event in 1054 CE, as did, almost certainly, Native Americans.
The orange filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the center of the nebula is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultradense core of the exploded star.
The Crab Nebula derived its name from its appearance in a drawing made by Irish astronomer Lord Rosse in 1844, using a 36inch telescope. When viewed by Hubble, as well as by large groundbased telescopes such as the European Southern Observatory's Very Large Telescope, the Crab Nebula takes on a more detailed appearance that yields clues into the spectacular demise of a star, 6,500 lightyears away.
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Artist's impression of "the oldest star of our Galaxy": HE 15230901
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This view of the rising Earth greeted the Apollo 8 astronauts as they came from behind the Moon after the fourth nearside orbit. Earth is about five degrees above the horizon in the photo. The unnamed surface features in the foreground are near the eastern limb of the Moon as viewed from Earth. The lunar horizon is approximately 780 kilometers from the spacecraft. Width of the photographed area at the horizon is about 175 kilometers. On the Earth 240,000 miles away, the sunset terminator bisects Africa.
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 the Mercury image was taken by Mariner 10,
 the Venus image by Magellan,
 the Earth and Moon images by Galileo,
 the Mars image by Mars Global Surveyor,
 the Jupiter image by Cassini, and
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 Earth 12,756.28 km
 Moon 3,476.2 km
 Mars 6,804.9 km
 Jupiter 142,984 km
 Saturn 120,536 km
 Uranus 51,118 km
 Neptune 49,528 km
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The KennedyThorndike experiment. Key optical components were mounted within vacuum chamber V on a fused quartz base of extremely low coefficient of thermal expansion. A water jacket W kept the temperature regulated to within 0.001°C. Monochromatic green light from a mercury source Hg passed through a Nicol polarizing prism N before entering the vacuum chamber, and was split by a beam splitter B set at Brewster's angle to prevent unwanted rear surface reflections. The two beams were directed towards two mirrors M_{1} and M_{2} which were set at distances as divergent as possible given the coherence length of the 5461 Å mercury line (≈32 cm, allowing a difference in arm length ΔL ≈ 16 cm). The reflected beams recombined to form circular interference fringes which were photographed at P. A slit S allowed multiple exposures across the diameter of the rings to be recorded on a single photographic plate at different times of day.
A diagram of the Michelson–Morley experiment.
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Lattice analogy of the deformation of spacetime caused by a planetary mass.