A few years ago I did some research into gravity and concluded with decent probability that gravity is extremely high frequencies, beyond anything we can presently even dream of detecting _as_ electromagnetic radiation. These are not gamma rays generated by black holes and such. It's been titled many names such as ZPE, quantum foam, aether, etc.
Although I don't recall some of the exact details of the research, I ran into numerous leading edge QM research that really shed light that gravity is caused by a push, from radiation. I firmly believe more than ever that conventional science will one day discover this sea of energy, perhaps in plasmic form, consisting of a whole new range of particles smaller than we've imagined that make up our electrons, protons, magnetism and electric forces, gravity, etc. This discovery is somewhat akin to going from the detection of galaxies to planet & sun size objects or from detecting sound waves to electromagnetic radiation or from detecting air currents to electrical currents, etc.; i.e., it will be a huge leap in our society just as when society changed from the discovery of electricity.
Although it now seems highly likely this sea of energy exists, I firmly believe nearly all legitimate so-called "free energy" devices are getting the energy from Magnetocaloric energy.
Paul Lowrance