Apergy

Apergy is a hypothetical repulsive force that represents an opposition to gravitation as an attractive force, sometimes described as the centripetal force to gravity's centrifugal force. According to the speculations on apergy, the two forces would neutralise one another, and an increase of apergy would produce an anti-gravity effect.

The early sources of apergetic theory are science fiction novels of the late nineteenth century, including Percy Greg's Across the Zodiac (1880) and John Jacob Astor's A Journey in Other Worlds (1894), as well as writings on John Worrell Keely's alleged discoveries during that same time period. Indeed, in certain sensationalist press coverage, Astor's purchase of Keely Motor Company stock was linked to the possibility that apergy was real and Keely had tapped into the secret of it.