Faster-than-light travel and communication are the conjectural propagation of matter or information faster than the speed of light. The special theory of relativity implies that only particles with zero rest mass may travel at the speed of light, and that nothing may travel faster.
General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations.
In physics, gravity (from Latin gravitas 'weight') is a fundamental interaction primarily observed as mutual attraction between all things that have mass. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a result, it has no significant influence at the level of subatomic particles. However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light.
Kip Stephen Thorne is an American theoretical physicist and writer known for his contributions in gravitational physics and astrophysics. Along with Rainer Weiss and Barry C. Barish, he was awarded the 2017 Nobel Prize in Physics for his contributions to the LIGO detector and the observation of gravitational waves.
Since the 19th century, some physicists, notably Albert Einstein, have attempted to develop a single theoretical framework that can account for all the fundamental forces of nature – a unified field theory. Classical unified field theories are attempts to create a unified field theory based on classical physics. In particular, unification of gravitation and electromagnetism was actively pursued by several physicists and mathematicians in the years between the two World Wars. This work spurred the purely mathematical development of differential geometry.
Richard Chace Tolman was an American mathematical physicist and physical chemist who made many contributions to statistical mechanics. He also made important contributions to theoretical cosmology in the years soon after Einstein's discovery of general relativity. He was a professor of physical chemistry and mathematical physics at the California Institute of Technology (Caltech).
Werner Israel, was a theoretical physicist known for his contributions to gravitational theory, and especially to the understanding of black holes.
Roy Patrick Kerr is a New Zealand mathematician who discovered the Kerr geometry, an exact solution to the Einstein field equation of general relativity. His solution models the gravitational field outside an uncharged rotating massive object, including a rotating black hole. His solution to Einstein's equations predicted spinning black holes before they were discovered.
Robert M. Wald is an American theoretical physicist and professor at the University of Chicago. He studies general relativity, black holes, and quantum gravity and has written textbooks on these subjects.
Ludwik Silberstein was a Polish-American physicist who helped make special relativity and general relativity staples of university coursework. His textbook The Theory of Relativity was published by Macmillan in 1914 with a second edition, expanded to include general relativity, in 1924.
General Relativity is a graduate textbook and reference on Albert Einstein's general theory of relativity written by the gravitational physicist Robert Wald.
Jürgen Ehlers was a German physicist who contributed to the understanding of Albert Einstein's theory of general relativity. From graduate and postgraduate work in Pascual Jordan's relativity research group at Hamburg University, he held various posts as a lecturer and, later, as a professor before joining the Max Planck Institute for Astrophysics in Munich as a director. In 1995, he became the founding director of the newly created Max Planck Institute for Gravitational Physics in Potsdam, Germany.
Bernard F. Schutz FInstP FLSW is an American and naturalised British physicist. He is well known for his research in Einstein's theory of general relativity, especially for his contributions to the detection of gravitational waves, and for his textbooks. Schutz is a Fellow of the Royal Society and a Member of the US National Academy of Sciences. He is a professor of physics and astronomy at Cardiff University, and was a founding director of the Max Planck Institute for Gravitational Physics in Potsdam, Germany, where he led the Astrophysical Relativity division from 1995 to 2014. Schutz was a founder and principal investigator of the GEO gravitational wave collaboration, which became part of the LIGO Scientific Collaboration (LSC). Schutz was also one of the initiators of the proposal for the space-borne gravitational wave detector LISA, and he coordinated the European planning for its data analysis until the mission was adopted by ESA in 2016. Schutz conceived and in 1998 began publishing from the AEI the online open access (OA) review journal Living Reviews in Relativity, which for many years has been the highest-impact OA journal in the world, as measured by Clarivate.
Øyvind Grøn is a Norwegian physicist.
Hořava–Lifshitz gravity is a theory of quantum gravity proposed by Petr Hořava in 2009. It solves the problem of different concepts of time in quantum field theory and general relativity by treating the quantum concept as the more fundamental so that space and time are not equivalent (anisotropic) at high energy level. The relativistic concept of time with its Lorentz invariance emerges at large distances. The theory relies on the theory of foliations to produce its causal structure. It is related to topologically massive gravity and the Cotton tensor. It is a possible UV completion of general relativity. Also, the speed of light goes to infinity at high energies. The novelty of this approach, compared to previous approaches to quantum gravity such as loop quantum gravity, is that it uses concepts from condensed matter physics such as quantum critical phenomena. Hořava's initial formulation was found to have side-effects such as predicting very different results for a spherical Sun compared to a slightly non-spherical Sun, so others have modified the theory. Inconsistencies remain, though progress was made on the theory. Nevertheless, observations of gravitational waves emitted by the neutron-star merger GW170817 contravene predictions made by this model of gravity. Some have revised the theory to account for this.
Criticism of the theory of relativity of Albert Einstein was mainly expressed in the early years after its publication in the early twentieth century, on scientific, pseudoscientific, philosophical, or ideological bases. Though some of these criticisms had the support of reputable scientists, Einstein's theory of relativity is now accepted by the scientific community.
Luis Alfredo "Gaucho" Herrera Cometta is a Venezuelan relativity physicist, whose research focuses on the study of anisotropy, the extended thermodynamics, exact and semi numeric solutions, axial symmetric solutions, alternative approaches to detect gravitational radiation using gyroscopes and recently about the relevance of super energy and super Poynting in General Relativity. Herrera is Emeritus Professor in the Escuela de Física at Universidad Central de Venezuela and currently is Visiting Professor at the Instituto Universitario de Fisica Fundamental y Matematicas, Universidad de Salamanca, Salamanca, Spain.
Arthur Baraway Komar was a theoretical physicist, specializing in general relativity and helping to develop the canonical approach to quantum gravity. Arthur Komar made a significant contribution to physics as an educator, research scientist, and administrator. He had wide interests in numerous other subjects, and his friends knew him as a renaissance man.
The Meaning of Relativity: Four Lectures Delivered at Princeton University, May 1921 is a book published by Princeton University Press in 1922 that compiled the 1921 Stafford Little Lectures at Princeton University, given by Albert Einstein. The lectures were translated into English by Edwin Plimpton Adams. The lectures and the subsequent book were Einstein's last attempt to provide a comprehensive overview of his theory of relativity and is his only book that provides an accessible overview of the physics and mathematics of general relativity. Einstein explained his goal in the preface of the book's German edition by stating he "wanted to summarize the principal thoughts and mathematical methods of relativity theory" and that his "principal aim was to let the fundamentals in the entire train of thought of the theory emerge clearly". Among other reviews, the lectures were the subject of the 2017 book The Formative Years of Relativity: The History and Meaning of Einstein's Princeton Lectures by Hanoch Gutfreund and Jürgen Renn.
