Anti-gravity

Anti-gravity is the concept of a force that would exactly oppose the force of gravity. Under the laws of general relativity, anti-gravity is impossible except under contrived circumstances.

Anti-gravity does not refer to either the lack of weight under gravity experienced in free fall or orbit, or to balancing the force of gravity with some other force, such as electromagnetism, aerodynamic lift, or ion-propelled "lifters", which fly in the air by moving air with electromagnetic fields.

Anti-gravity is a recurring concept in science fiction.

Under the laws of general relativity, anti-gravity is impossible except under contrived circumstances. Under that theory, and particle physics, gravity is mass-energy, a quantity believed to always be positive. It is always attractive and never repulsive.

Generally attempts have been tried to "quantize gravity" by positing a particle, the graviton, that carried gravity in the same way that photons (light) carry electromagnetism. Simple attempts along this direction all failed, however, leading to more complex examples that attempted to account for these problems. Two of these, supersymmetry and the relativity related supergravity, both required the existence of an extremely weak "fifth force" carried by a graviphoton, which coupled together several "loose ends" in quantum field theory, in an organized manner. As a side effect, both theories also all but required that antimatter be affected by this fifth force in a way similar to anti-gravity, dictating repulsion away from mass. Several experiments were carried out in the 1990s to measure this effect, but none yielded positive results.^{[improper synthesis?]}

During the close of the twentieth century NASA provided funding for the Breakthrough Propulsion Physics Program (BPP) from 1996 through 2002. This program studied a number of "far out" designs for space propulsion that were not receiving funding through normal university or commercial channels. Anti-gravity-like concepts were listed under "approaches categorized as non-viable" since the study found found no evidence of a anti-gravity-like forces.

In 2013 CERN looked for an antigravity effect in an experiment designed to study the energy levels within antihydrogen. The antigravity measurement was just an "interesting sideshow" and was inconclusive.

There have been a number of studies, attempts to build anti-gravity devices, and a small number of reports of anti-gravity-like effects in popular and scientific literature. None of the examples that follow are accepted as reproducible examples of anti-gravity.