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Gravitational Waves Gravitational waves Gravitational waves are the disturbance in the fabric ("curvature") of spacetime generated by accelerated masses and propagate as waves outward from their source at the speed of light [...More...]  "Gravitational Waves" on: Wikipedia Yahoo Parouse 

Gravity Wave In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves. A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a wave orbit.[1] Gravity Gravity waves on an air–sea interface of the ocean are called surface gravity waves or surface waves, while gravity waves that are within the body of the water (such as between parts of different densities) are called internal waves [...More...]  "Gravity Wave" on: Wikipedia Yahoo Parouse 

Gravitational Compression Gravitational Gravitational compression is a phenomenon in which gravity, acting on the mass of an object, compresses it, reducing its size and increases the object's density.In the core of a star such as the Sun, gravitational pressure is balanced by the outward thermal pressure from fusion reactions, temporarily halting gravitational compression.At the center of a planet or star, gravitational compression produces heat by the Kelvin–Helmholtz mechanism. This is the mechanism that explains how Jupiter Jupiter continues to radiate heat produced by its gravitational compression.[1] The most common reference to gravitational compression is stellar evolution. The Sun Sun and other mainsequence stars are produced by the initial gravitational collapse of a molecular cloud [...More...]  "Gravitational Compression" on: Wikipedia Yahoo Parouse 

Gravitational Redshift In astrophysics, gravitational redshift or Einstein shift is the process by which electromagnetic radiation originating from a source that is in a gravitational field is reduced in frequency, or redshifted, when observed in a region at a higher gravitational potential. This is a direct result of gravitational time dilation—if one is outside an isolated gravitational source, the rate at which time passes increases as one moves away from that source. As frequency is inverse of time (specifically, time required for completing one wave oscillation), frequency of the electromagnetic radiation is reduced in an area of higher gravitational potential [...More...]  "Gravitational Redshift" on: Wikipedia Yahoo Parouse 

Redshift In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum. In general, whether or not the radiation is within the visible spectrum, "redder" means an increase in wavelength – equivalent to a lower frequency and a lower photon energy, in accordance with, respectively, the wave and quantum theories of light. Some redshifts are an example of the Doppler effect, familiar in the change of apparent pitches of sirens and frequency of the sound waves emitted by speeding vehicles. A redshift occurs whenever a light source moves away from an observer. A special instance of this is the cosmological redshift, which is due to the expansion of the universe, and sufficiently distant light sources (generally more than a few million light years away) show redshift corresponding to the rate of increase in their distance from Earth [...More...]  "Redshift" on: Wikipedia Yahoo Parouse 

Blueshift A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift. In visible light, this shifts the color from the red end of the spectrum to the blue end.Contents1 Doppler blueshift 2 Gravitational blueshift2.1 Blue outliers3 Cosmological blueshift 4 See also 5 NotesDoppler blueshift[edit]Doppler redshift and blueshiftDoppler blueshift is caused by movement of a source towards the observer. The term applies to any decrease in wavelength and increase in frequency caused by relative motion, even outside the visible spectrum [...More...]  "Blueshift" on: Wikipedia Yahoo Parouse 

Time Dilation According to the theory of relativity, time dilation is a difference in the elapsed time measured by two observers, either due to a velocity difference relative to each other, or by being differently situated relative to a gravitational field. As a result of the nature of spacetime,[2] a clock that is moving relative to an observer will be measured to tick slower than a clock that is at rest in the observer's own frame of reference [...More...]  "Time Dilation" on: Wikipedia Yahoo Parouse 

Gravitational Time Dilation Gravitational time dilation Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass. The higher the gravitational potential (the farther the clock is from the source of gravitation), the faster time passes. Albert Einstein Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity.[1] This has been demonstrated by noting that atomic clocks at differing altitudes (and thus different gravitational potential) will eventually show different times. The effects detected in such Earthbound experiments are extremely small, with differences being measured in nanoseconds [...More...]  "Gravitational Time Dilation" on: Wikipedia Yahoo Parouse 

Gravitational Potential In classical mechanics, the gravitational potential at a location is equal to the work (energy transferred) per unit mass that would be needed to move the object from a fixed reference location to the location of the object. It is analogous to the electric potential with mass playing the role of charge. The reference location, where the potential is zero, is by convention infinitely far away from any mass, resulting in a negative potential at any finite distance. In mathematics, the gravitational potential is also known as the Newtonian potential and is fundamental in the study of potential theory [...More...]  "Gravitational Potential" on: Wikipedia Yahoo Parouse 

Naked Singularity In general relativity, a naked singularity is a gravitational singularity without an event horizon. In a black hole, the singularity is completely enclosed by a boundary known as the event horizon, inside which the gravitational force of the singularity is so strong that light cannot escape. Hence, objects inside the event horizon—including the singularity itself—cannot be directly observed. A naked singularity, by contrast, is observable from the outside. The theoretical existence of naked singularities is important because their existence would mean that it would be possible to observe the collapse of an object to infinite density. It would also cause foundational problems for general relativity, because general relativity cannot make predictions about the future evolution of spacetime near a singularity [...More...]  "Naked Singularity" on: Wikipedia Yahoo Parouse 

Gravitoelectromagnetism Gravitoelectromagnetism, abbreviated GEM, refers to a set of formal analogies between the equations for electromagnetism and relativistic gravitation; specifically: between Maxwell's field equations Maxwell's field equations and an approximation, valid under certain conditions, to the Einstein field equations for general relativity. Gravitomagnetism is a widely used term referring specifically to the kinetic effects of gravity, in analogy to the magnetic effects of moving electric charge [...More...]  "Gravitoelectromagnetism" on: Wikipedia Yahoo Parouse 

Space Space Space is the boundless threedimensional extent in which objects and events have relative position and direction.[1] Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless fourdimensional continuum known as spacetime. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Debates concerning the nature, essence and the mode of existence of space date back to antiquity; namely, to treatises like the Timaeus of Plato, or Socrates Socrates in his reflections on what the Greeks called khôra (i.e [...More...]  "Space" on: Wikipedia Yahoo Parouse 

Time Time Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future.[1][2][3] Time Time is a component quantity of various measurements used to sequence e [...More...]  "Time" on: Wikipedia Yahoo Parouse 

Minkowski Diagram The Minkowski diagram, also known as a spacetime diagram, was developed in 1908 by Hermann Minkowski Hermann Minkowski and provides an illustration of the properties of space and time in the special theory of relativity. It allows a qualitative understanding of the corresponding phenomena like time dilation and length contraction without mathematical equations. Minkowski diagrams are a twodimensional graph that depict events as happening in a universe consisting of one space dimension and one time dimension. Unlike a regular distancetime graph, the distance will be displayed on the horizontal axis and time on the vertical axis. Additionally, the time and space units of measurement are chosen in such a way that an object moving at the speed of light is depicted as following a 45° angle to the diagram's axes. In this way, each object, like an observer or a vehicle, traces a certain line in the diagram, which is called its world line [...More...]  "Minkowski Diagram" on: Wikipedia Yahoo Parouse 

Minkowski Space In mathematical physics, Minkowski space Minkowski space (or Minkowski spacetime) is a combining of threedimensional Euclidean space Euclidean space and time into a fourdimensional manifold where the spacetime interval between any two events is independent of the inertial frame of reference in which they are recorded. Although initially developed by mathematician Hermann Minkowski for Maxwell's equations Maxwell's equations of electromagnetism, the mathematical structure of Minkowski spacetime was shown to be an immediate consequence of the postulates of special relativity.[1] Minkowski space Minkowski space is closely associated with Einstein's theory of special relativity, and is the most common mathematical structure on which special relativity is formulated [...More...]  "Minkowski Space" on: Wikipedia Yahoo Parouse 

Closed Timelike Curve In mathematical physics, a closed timelike curve (CTC) is a world line in a Lorentzian manifold, of a material particle in spacetime that is "closed", returning to its starting point. This possibility was first discovered by Willem Jacob van Stockum Willem Jacob van Stockum in 1937[1] and later confirmed by Kurt Gödel Kurt Gödel in 1949,[2] who discovered a solution to the equations of general relativity (GR) allowing CTCs known as the Gödel metric; and since then other GR solutions containing CTCs have been found, such as the Tipler cylinder and traversable wormholes. If CTCs exist, their existence would seem to imply at least the theoretical possibility of time travel backwards in time, raising the spectre of the grandfather paradox, although the Novikov selfconsistency principle seems to show that such paradoxes could be avoided [...More...]  "Closed Timelike Curve" on: Wikipedia Yahoo Parouse 