Anti-gravity

Anti-gravity is the phenomenon of creating a place or object that is free from the force of gravity. It does not refer to 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 or aerodynamic lift, for example in vactrains.

Gyroscopic perpetual motion devices produce a force when twisted that operates "out of plane" and lift themselves against gravity.

The antimatter counterpart of every matter particle should have the same mass, the same acceleration in a gravitational field, the opposite electric charge, the opposite spin, the same magnetic properties, same binding. If the gravitational acceleration comes back negative, negative gravitational mass causes antimatter to anti-gravitate, falling up instead of down, and gravity sees it as though it were made of anti-mass or anti-energy. Such a breakthrough has led to gravitational conductors, uniform artificial gravity fields for megastructures or space habitats, and the first Alcubierre warp drives.

Neutronium plates could also be used to design a local antigravity field. If a 0.4 mm-thick neutronium disk were placed above ground, the gravity beneath the sheet would be zero, the upward 1-gee pull of the neutronium exactly canceling the 1-gee downward pull of the Earth.

Electrogravitics is an effect or type of anti-gravity force created by an electric field's effect on a mass. The name was coined in the 1920s by the discoverer of the effect, Thomas Townsend Brown, who spent most of his life trying to develop it and sell it as a propulsion system. It was researched for a short while by aerospace companies in the 1950s. Secrets of Antigravity Propulsion by Paul LaViolette talks about Brown's inventions in great detail.