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Mach's Principle In theoretical physics, particularly in discussions of gravitation theories, Mach's principle Mach's principle (or Mach's conjecture[1]) is the name given by Einstein to an imprecise hypothesis often credited to the physicist and philosopher Ernst Mach. The idea is that local inertial frames are determined by the largescale distribution of matter, as exemplified by this anecdote:[citation needed]You are standing in a field looking at the stars. Your arms are resting freely at your side, and you see that the distant stars are not moving. Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move? Mach's principle Mach's principle says that this is not a coincidence—that there is a physical law that relates the motion of the distant stars to the local inertial frame [...More...]  "Mach's Principle" on: Wikipedia Yahoo 

Theoretical Physics Theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experimental tools to probe these phenomena. The advancement of science generally depends on the interplay between experimental studies and theory [...More...]  "Theoretical Physics" on: Wikipedia Yahoo 

Holism Holism Holism (from Greek ὅλος holos "all, whole, entire") is the idea that systems (physical, biological, chemical, social, economic, mental, linguistic) and their properties should be viewed as wholes, not just as a collection of parts.[1][2] The term holism was coined by J. C. Smuts in Holism Holism and Evolution.[3][4] It was Smuts' opinion that holism is a concept that represents all of the wholes in the universe, and these wholes are the real factors in the universe. Further, that Holism Holism also denoted a theory of the universe in the same vein as Materialism and Spiritualism.[3]:120–121 The derived adjective holistic has been applied to a wide range of fields where they incorporate the concept of holism [...More...]  "Holism" on: Wikipedia Yahoo 

Luminiferous Aether In the late 19th century, luminiferous aether, aether, or ether, meaning lightbearing aether, was the postulated medium for the propagation of light.[1] It was invoked to explain the ability of the apparently wavebased light to propagate through empty space, something that waves should not be able to do. The assumption of a spatial plenum of luminiferous aether, rather than a spatial vacuum, provided the theoretical medium that was required by wave theories of light. The concept was the topic of considerable debate throughout its history, as it required the existence of an invisible and infinite material with no interaction with physical objects. As the nature of light was explored, especially in the 19th century, the physical qualities required of the aether became increasingly contradictory [...More...]  "Luminiferous Aether" on: Wikipedia Yahoo 

Hubble Time Hubble's law Hubble's law is the name for the observation in physical cosmology that:Objects observed in deep space  extragalactic space, 10 megaparsecs (Mpc) or more  are found to have a red shift, interpreted as a relative velocity away from Earth; This Dopplershiftmeasured velocity of various galaxies receding from the Earth [...More...]  "Hubble Time" on: Wikipedia Yahoo 

Gravitational Constant The gravitational constant, also known as the universal gravitational constant, or as Newton's constant, denoted by the letter G, is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's general theory of relativity [...More...]  "Gravitational Constant" on: Wikipedia Yahoo 

Cauchy Surface Intuitively, a Cauchy surface is a plane in spacetime which is like an instant of time; its significance is that giving the initial conditions on this plane determines the future (and the past) uniquely. More precisely, a Cauchy surface is any subset of spacetime which is intersected by every inextensible, nonspacelike (i.e [...More...]  "Cauchy Surface" on: Wikipedia Yahoo 

Globally Hyperbolic Manifold In mathematical physics, global hyperbolicity is a certain condition on the causal structure of a spacetime manifold (that is, a Lorentzian manifold). This is relevant to Einstein's theory of general relativity, and potentially to other metric gravitational theories.Contents1 Definitions 2 Remarks 3 See also 4 ReferencesDefinitions[edit] There are several equivalent definitions of global hyperbolicity. Let M be a smooth connected Lorentzian manifold without boundary. We make the following preliminary definitions:M is causal if it has no closed causal curves. M is nontotal imprisoning if no inextendible causal curve is contained in a compact set. This property implies causality. M is strongly causal if for every point p and any neighborhood U of p there is a causally convex neighborhood V of p contained in U, where causal convexity means that any causal curve with endpoints in V is entirely contained in V [...More...]  "Globally Hyperbolic Manifold" on: Wikipedia Yahoo 

Compact Space In mathematics, and more specifically in general topology, compactness is a property that generalizes the notion of a subset of Euclidean space being closed (that is, containing all its limit points) and bounded (that is, having all its points lie within some fixed distance of each other). Examples include a closed interval, a rectangle, or a finite set of points. This notion is defined for more general topological spaces than Euclidean space Euclidean space in various ways. One such generalization is that a topological space is sequentially compact if every infinite sequence of points sampled from the space has an infinite subsequence that converges to some point of the space. The Bolzano–Weierstrass theorem Bolzano–Weierstrass theorem states that a subset of Euclidean space is compact in this sequential sense if and only if it is closed and bounded [...More...]  "Compact Space" on: Wikipedia Yahoo 

Asymptotically Flat Spacetime An asymptotically flat spacetime is a Lorentzian manifold in which, roughly speaking, the curvature vanishes at large distances from some region, so that at large distances, the geometry becomes indistinguishable from that of Minkowski spacetime. While this notion makes sense for any Lorentzian manifold, it is most often applied to a spacetime standing as a solution to the field equations of some metric theory of gravitation, particularly general relativity. In this case, we can say that an asymptotically flat spacetime is one in which the gravitational field, as well as any matter or other fields which may be present, become negligible in magnitude at large distances from some region [...More...]  "Asymptotically Flat Spacetime" on: Wikipedia Yahoo 

Elliptic Partial Differential Equation Second order linear partial differential equations (PDEs) are classified as either elliptic, hyperbolic, or parabolic [...More...]  "Elliptic Partial Differential Equation" on: Wikipedia Yahoo 

Coriolis Force In physics, the Coriolis force Coriolis force is an inertial force[1] that acts on objects that are in motion relative to a rotating reference frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the object. In one with anticlockwise (or counterclockwise) rotation, the force acts to the right. Deflection of an object due to the Coriolis force Coriolis force is called the Coriolis effect. Though recognized previously by others, the mathematical expression for the Coriolis force Coriolis force appeared in an 1835 paper by French scientist GaspardGustave de Coriolis, in connection with the theory of water wheels [...More...]  "Coriolis Force" on: Wikipedia Yahoo 

Precession Precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torquefree and torqueinduced. In astronomy, precession refers to any of several slow changes in an astronomical body's rotational or orbital parameters [...More...]  "Precession" on: Wikipedia Yahoo 

Discussions Debate is contention in argument; strife, dissension, quarrelling, controversy; especially a formal discussion of subjects before a public assembly or legislature, in Parliament or in any deliberative assembly.[1] Logical consistency, factual accuracy and some degree of emotional appeal to the audience are elements in debating, where one side often prevails over the other party by presenting a superior "context" or framework of the issue. In a formal debating contest, there are rules for participants to discuss and decide on differences, within a framework defining how they will interact. Debating is carried out in debating chambers and assemblies of various types to discuss matters and to make resolutions about action to be taken, often by voting.[citation needed] Deliberative bodies such as parliaments, legislative assemblies, and meetings of all sorts engage in debates. In particular, in parliamentary democracies a legislature debates and decides on new laws [...More...]  "Discussions" on: Wikipedia Yahoo 

Thought Experiment A thought experiment (German: Gedankenexperiment,[1] GedankenExperiment[2] or Gedankenerfahrung[3]) considers some hypothesis, theory,[4] or principle for the purpose of thinking through its consequences [...More...]  "Thought Experiment" on: Wikipedia Yahoo 

Philosophiae Naturalis Principia Mathematica Philosophiæ Naturalis Principia Mathematica Principia Mathematica (English pronunciation /fɪləˈsɒfi.aɪ nætʃəˈrɑːlɪs prɪnˈkɪpiə mæθəˈmætɪkə/, Latin Latin for Mathematical Principles of Natural Philosophy),[1] often referred to as simply the Principia, is a work in three books by [...More...]  "Philosophiae Naturalis Principia Mathematica" on: Wikipedia Yahoo 