Anti-gravity is a hypothetical force to counter the effects of gravity, typically in the context of spacecraft propulsion. Such systems are limited to the realm of science fiction given the current understanding of the way gravity works, but this has not stopped legions of hopefuls from making various spinning disks and magnets in hopes of perfecting such a device.

Gravitation was once thought to be a force between two objects. That is, something, gravity, creates a force on objects, causing them to move together. Under this Newtonian version of gravity it seems reasonable to suspect that it may be possible to create a system to interfere with this force, thereby lessening the effects of gravity on an object. An example of such a material, cavorite, is a major deus ex machina of H. G. Wells' famous book, The First Men in the Moon.

However Newtonian gravitation is no longer thought to be correct. In 1915 Albert Einstein published his work on general relativity which proposed an entirely new mechanism for gravity - 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: time. You stick to the floor not because gravity is pulling you down, but because that is the shortest distance between today and tomorrow. Under this model, gravity in a universe containing only matter with positive mass is purely attractive. While the paths of objects in regions with negative spacetime curvature diverge (producing an apparent tidal force pulling apart objects), this is a manifestation of the objects' attraction to some larger body. True antigravity in general relativity requires negative mass.

Not to be stopped, many anti-gravity aficionados have moved onto various quantum gravity theories in order to keep the dream alive. To date, none of these theories have proven fruitful.

The United States government and aerospace contractors publicly announced ambitious Manhattan project-style goals to crack the anti-gravity problem during the mid-1950's 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. Either their work never produced anything, or the projects were taken into the world of top secret. Few mentions of the subject surfaced until the 1990's when a Russian emigre scientist Eugene Podkletnov reported gravity shielding with spinning superconductors, Podkletnov claims he saw tobacco smoke rise over the spinning superconductor, so he measured the gravitational acceleration above the device and made the discovery. Podkletnov now claims to have created a force beam that is 200 times stronger than his first experiments. Another American scientist Ning Li had independently predicted a gravity shielding effect with superconductors at nearly the same time. Another one wanted to use superfluid helium in a toroidal vessel to create gravity control in the 1970's. Dr Robert L. Forward proposed using degenerate matter for gravity control. Since then, NASA, Boeing, and BAe have all funded Podkletnov reproduction experiments, with little to no results.

Anti-gravity effects may exist on a bigger scale, however. According to current theories, a repulsive force exercised on all matter by dark energy keeps our Universe expanding.

See also

• Jeff Cook Effect
• negative mass.

External links

• http://www.antigravity.org (big spin model explained)
• http://www.space-mixing-theory.com/abstract2.htm (apparent weight loss in charged capacitors)
• http://groups.yahoo.com/group/electrogravityresearch (discussions on the first antigravity device ever put on the public market)