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Anti-gravity is a recurring theme in science fiction, particularly in the context spacecraft propulsion. Often a special "gravity shield" or "anti-gravity force field" cancels the effects of gravity, allowing a spacecraft to accelerate (cf. warp drive). Unfortunately science has as yet failed to find any such force, and the present laws of physics appear to rule out the possibility of anti-gravity. Nonetheless, some have studied possible methods of achieving such effects. H.G. Wells and cavorite Newton's Law of Gravitation considered gravity to be a force between two objects, causing attraction in proportion to the objects' mass. Under this interpretation, an object with negative mass would repel ordinary matter, and could be used to produce an anti-gravity effect. Alternatively, depending on the mechanism assumed to underlie the gravitational force, it may seem reasonable to postulate a material that shields against gravity or otherwise interferes with the force. An example of such a material, cavorite, is a major element in H. G. Wells' famous book, The First Men in the Moon, although cavorite isn't consistent with even a Newtonian view of the universe—it causes violations of conservation laws. Neither negative-mass exotic matter nor gravity-screening material have been observed experimentally. While the potential existence of exotic matter is still debated, general relativity presents persuasive arguments against the existence of screening materials. Some proposed models of anti-gravity Einstein's theory of general relativity, published in 1915, supplanted Newton's model of gravity with an entirely different mechanism, one based entirely on the geometry of the universe. Gravity was no longer a force at all, but simply the consequence of the local slope of the universe in a direction the human eye cannot see: a fourth spatial dimension. Under this model, gravity in a universe containing only matter with positive mass is purely attractive. No arrangement of ordinary matter can produce an anti-gravity effect. Spacetime geometries corresponding to true anti-gravity in general relativity require negative mass. Some models of anti-gravity claim to derive from general relativity. The model of gravity proposed by the theory of general relativity breaks down under extreme conditions (too far inside a black hole, and in the very early life of the universe under the big bang model). The rapid expansion of the early universe (cosmic inflation) has been verified by the WMAP result; however, no satisfactory explanations have been found as of 2006. Galaxy rotation problem is a case where the Spiral galaxy rotation observations do not fit well with traditional gravitation theory. Most physicists believe that at extremely high energies, gravity and the other fundamental forces unify, which would allow gravity to be manipulated in ways that are not readily apparent now. Candidate models for this regime are theories of everything, which attempt to model all four forces (example: string theory), and theories of quantum gravity, which attempt to produce a model of gravity that is consistent with quantum mechanics, though not necessarily unified with the other forces. Some models of anti-gravity claim to be based on quantum gravity models, though the connection of these to mainstream quantum gravity models is often tenuous. Conventional effects that mimic anti-gravity effects Anti-gravity in the context of non-mainstream physics The United States government and aerospace contractors publicly announced ambitious Manhattan project-style goals to crack the anti-gravity problem during the mid-1950s while the atomic airplane was on the drawing board, but by the end of 1957, no more information was flowing into the newspapers and magazines. According to the aviation trade publication Interavia, research into "electro-gravitic propulsion" was done in 1956. "In this particular line of research, the weights of some materials have already been cut as much as 30 percent by 'energizing' them. Security prevents disclosure of what precisely is meant by 'energizing' or in which country this work is under way," the magazine reported. A localized gravitic field used as a ponderamotive force has been created. In 1999, Li and her team appeared in Popular Mechanics, having constructed a working prototype to generate what she describes as "AC Gravity". The device is known as the high temperature superconducting disc. Li acknowledges that to 'release' the device before knowing that it is indeed functional and not an unexplained aberration could cause a situation similar to the cold fusion discoveries. * In 2001, the Disclosure Project announced that Anti-Gravity and Zero-point energy were in use by secret government agencies for UFOs. The claim, backed up by 400 credible witnesses, has yet to be taken seriously. In November 2005, the United States Patent and Trademark Office (USPTO) granted Boris Volfson, an American inventor, for an anti-gravity device. The patent was an embarrassment to the Patent Office as it is quite clearly an infinite energy source or a perpetual motion machine, thus defying the laws of physics, as pointed out by Robert L. Park, * * *. See also Mainstream links on gravity-related research Non-mainstream antigravity As the effects described by the following links haven't been replicated or published in peer-reviewed journals, they are often derided as pseudoscience. Proponents characteristically complain their models are dismissed out of hand without attempts at replication by the mainstream scientific community and thus have not been disproven. | |||||||
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