Discovering possible new forces in nature is no mean task. The discovery of gravity linked to Newton's arguably apocryphal apple experiment has remained anchored in popular culture. In January 1986, Ephraim Fischbach, Physics Professor from Purdue University in West Lafayette, Indiana, had his own chance to leave his mark on collective memory. His work made the front page of the New York Times after he and his co-authors published a study uncovering the tantalising possibility of the existence of a fifth force in the universe. In an article published in *EPJ H*, Fischbach gives a personal account of how the existence of the gravity-style fifth force has stimulated an unprecedented amount of research in gravitational physics - even though its existence, as initially formulated, has not been confirmed by experiment.
Back in the late 1980s, Fischbach and colleagues reanalysed data from a classical physics study, known as the Eötvös Experiment, comparing the accelerations of samples of different chemical compositions to the Earth. His interpretation went against previous understanding, suggesting that acceleration varies depending on the elements' chemical composition. In theory, this force would coexist with gravity, but it would appear in an experiment in the form of a gravity-like long-range force, whose effects would extend over macroscopic distances. It was attributed to the exchange of any of the ultra-light quanta, which are predicted in theories that unify all existing forces under a single, consistent theoretical framework. About thirty years of research later, there is no evidence for the existence of any deviation from the predictions of standard gravity at any distance scale. Nor is there any experimental confirmation for the original model for a fifth force, which would be proportional to the number of baryons in the interacting samples. However, it remains possible that a different kind of fifth force, of a different nature than originally envisaged, could still exist. Meanwhile, this hypothetical force <http://phys.org/tags/force/> has led to the development of many new theories and novel experiments. For instance, it has stimulated the quest for new macroscopic fields of gravitational strength, and provides another means of studying high-energy physics. Read more at: http://phys.org/news/2015-10-may-the-fifth-force-be.html#jCp There has been a concept recently introduced by the AIRBUS people in LENR thinking called "Dark Gravity". This force is a rethinking of the general theory of relativity to include the concept of negative energy in the formulation of einstein's equations. The concept of negative energy came about in Dirac's formulation of the electron theory at relativistic speeds. The concepts of the tachyon explains how the removal of all quantum uncertainty from the inside of a black hole produces negative energy. Negative energy is absolute "nothing". this negative energy is also negative matter. Time runs backward inside a black hole as a result of an accumulation of negative energy. Negative energy flips things around. Feynman said that a positron is an electron that is traveling backward in time. From this ground rule of quantum mechanics, negative energy flips the charge of the electron around when the electron goes backward in time. Negative mass also flips the direction of gravity around from attractive to repulsive. When the LENR reaction is underway in matter where tachyons are produced in micro black holes, those tachyons produce a repulsive force that counters the force of gravity. This repulsive force is called "Dark Gravity". This might be the fifth force that is being produced in matter when LENR is active in various chemical compounds when certain catalytic processes are underway.
