James F. Woodward’s research while affiliated with California State University, Fullerton and other places

In a recent issue of this journal, Rodal (Gen Relativ Gravit 51:61–84, 2019) has written an extensive critique of a novel propulsion scheme devised nearly 30 years ago (Woodward in Found Phys Lett 6:1–39, 1995; Making starships and stargates: the science of interstellar transport and absurdly benign wormholes, Springer, New York, 2012). That scheme depends on the production of rest mass fluctuations, driven in special systems, that arise when the systems are accelerated, through the interaction of the systems with the field that produces inertial forces. Following Einstein, the field that produces inertial forces is taken to be the gravitational field due chiefly to the most distant matter (everything that gravitates) in the universe. Such rest mass fluctuations in local accelerating objects, predicted using the relativistic Newtonian approximation to general relativity, are now called “Mach effects” since they depend on inertial forces in fact being gravitational forces as Ernst Mach hinted might be the case. Rodal claims that such rest mass fluctuations with significant magnitude, save in the vicinity of black holes, are not to be found in general relativity notwithstanding that they appear in the relativistic Newtonian approximation. Rodal is mistaken in this claim, as I have already explained at some length (Woodward in J Br Interplanet Soc 70:354–364, 2018). Here I recapitulate some of that material and expand some material with specific reference to his now published claims.

There has been some interest in "breakthrough" or "exotic" propulsion - propulsion that does not involve ejecting a large amount of propellant from a craft to accelerate it - since the mid-twentieth century. To be clear we are not talking about nuclear (fission, fusion, antimatter annihilation) beamed energy propulsion sails, electromagnetic (ion, Hall thrusters, pulsed plasma) rockets or Casimir or Dynamic Casimir effect drives (referring to work by Jordan Maclay). These propulsion methods are often referred to as "advanced". Breakthrough propulsion involves either "new" physics, or a new way of understanding well-established physics. For many years, the underlying physics of breakthrough propulsion has been taken to be the physics of the "quantum vacuum". However, the version of the "quantum vacuum" advocated by the majority of exotic propulsion physicists (and engineers) is not the standard physics of the vacuum of quantum electrodynamics (QED), electroweak or chromodynamics (QCD) or, more generally, quantum field theory (QFT). Early work of this sort focused upon a stochastic electrodynamics model, developed in the 1980's and 90's, a classical way to treat the quantum vacuum zero-point fluctuations. One application of that model was an attempt to show that inertia could be described as zero-point-field Lorentz force. The implication being that inertia was taken to be electromagnetic in origin, rather than gravitational. This was refuted a decade and a half ago - but is included here for completeness. More recent work, by H. White, on the quantum vacuum has focused on the putative "plasma" of electron-positron (e-p) pairs that allegedly can be "densified" by the action of macroscopic electromagnetic fields on certain materials. We show, by employing only the Heisenberg Uncertainty Principle, that this proposal too leads to incorrect results.

Einstein believed that his general relativity theory contained the essence of Mach's ideas. That a mass is determined by the rest of the mass-energy content of the universe. Inertia here arises from mass-energy there. The latter, an opinion shared by John Wheeler. Einstein believed that to be fully Machian, gravity would need a radiative component, an action-at-a-distance character, so that gravitational influences from far away could be felt immediately by a particle. Hoyle and Narlikar in the 1960's developed such a theory which was a gravitational version of the Absorber theory derived by Wheeler–Feynman for classical electrodynamics. Hawking in 1965 showed that the mass, from the advanced wave integral in the Hoyle Narlikar theory, was divergent. It can be shown that the advanced wave integral is finite when the cosmic event horizon, due to the acceleration of the universe, is taken into consideration. The HN-theory is directly related to the mass fluctuation equations in the Woodward Mach effect thruster theory. The connection between the theories will be made clear, also presented is new experimental data from the past 6 months.

The Mach Effect Thruster [1, 2, 3, 4] (MET) is a device which uses Mach's principle in Einstein's General Relativity to produce a constant acceleration in a device which is undergoing internal energy changes and mass fluctuations. Mach's principle is a statement that the inertia of a body is the result of the gravitational interaction of the body with the rest of the mass-energy in the universe. The MET device requires no fuel as a propellant needing only electric power of 100-200 Watts to operate. The thrusts at the present time are small-on the order of a few micro-Newtons. The first part of the paper is devoted to experiment and a description of the MET device and apparatus for measuring thrusts. In the second half of the paper, we reintroduce the idea of advanced waves, by summarizing Dirac, Wheeler-Feynman and Hoyle-Narlikar (HN). We show how Woodward's mass fluctuation formula can be derived from first principles using the HN-theory which is a fully Machian version of Einstein's relativity. HN-theory reduces to Einstein's field equations in the limit of smooth fluid distribution of matter and a simple coordinate transformation. PACS codes: 04.20.-q, 04.20.Cv, 04.30.-w, 04.40.Nr Classical GR = 4.20.-q, Fund. problems and general formalism GR = 4.20.Cv, G-waves theory = 4.30,-w Radiation Fields = 4.40.Nr

The Mach Effect Thruster (MET) is a device which utilizes fluctuations in the rest masses of accelerating objects (capacitor stacks, in which internal energy changes take place) to produce a steady linear thrust. The theory has been given in detail elsewhere [1, 2] and references therein, so here we discuss only an experiment. We show how to obtain thrust using a heavy reaction mass at one end of our capacitor stack and a lighter end cap on the other. Then we show how this thrust can be eliminated by having two heavy masses at either end of the stack with a central mounting bracket. We show the same capacitor stack being used as a thruster and then eliminate the thrust by arranging equal brass masses on either end, so that essentially the capacitor stack is trying to push in both directions at once. This arrangement in theory would only allow for a small oscillation but no net thrust. We find the thrust does indeed disappear in the experiment, as predicted. The device (in thruster mode) could in principle be used for propulsion [1, 2]. Experimental apparatus based on a very sensitive thrust balance is briefly described. The experimental protocol employed to search for expected Mach effects is laid out, and the results of this experimental investigation are described.

The theory underlying Mach effects – fluctuations of the restmasses of accelerating objects in which internal energy changes take place – and their use for propulsion is briefly recapitulated. Experimental apparatus based on a very sensitive thrust balance is briefly described. The experimental protocol employed to search for expected Mach effects is laid out, and the results of this experimental investigation are presented. A series of tests conducted to explore the origin of the thrust signals seen are described, and two of those tests – the most likely spurious sources of thrust signals – are considered in some detail. The thrust signals seen, if genuine Mach effects, suggest that "advanced and exotic" propulsion can be achieved with realistic resources. Nomenclature A g = gravimagnetic (three) vector potential a = acceleration (bold: three vector acceleration) c = vacuum speed of light  = gradient operator 0 m  = mass fluctuation ds = distance differential E = energy E g = gravelectric field strength F = three vector accelerating force F = four vector gravitational field strength f = three vector (spatial) gravitational field strength G = Newton's constant of universal gravitation K p = piezoelectric constant (d 33) K e = electrostriction constant m = mass M = mass of the universe P = power  = scalar gravitational potential r = radial distance R = radius of the universe  = "matter" density v = three velocity V = volume, or voltage (context dependent)

Extremely short throat “absurdly benign” wormholes enabling near instantaneous travel to arbitrarily remote locations in both space and time – stargates – have long been a staple of science fiction. The physical requirements for the production of such devices were worked out by Morris and Thorne in 1988. They approached the issue of rapid spacetime transport by asking the question: what constraints do the laws of physics as we know them place on an “arbitrarily advanced culture” (AAC)? Their answer – a Jupiter mass of negative restmass matter in a structure a few tens of meters in size – seems to have rendered such things beyond the realm of the believably achievable. This might be taken as justification for abandoning further serious exploration of the physics of stargates. If such an investigation is pursued, however, one way to do so is to invert Morris and Thorne's question and ask: if “arbitrarily advanced aliens” (AAAs) have actually made stargates, what must be true of the laws of physics for them to have done so? Elementary arithmetic reveals that stargates would have an “exotic” density of on the order of 1022 gm/cm3, that is, orders of magnitude higher than nuclear density. Not only does one have to achieve this stupendous density of negative mass matter, it must be done, presumably, only with the application of “low” energy electromagnetic fields. We examine this problem, finding that a plausible solution does not depend on the laws of quantum gravity, as some have proposed. Rather, the solution depends on understanding the nature of electrons in terms of a semi-classical extension of the exact, general relativistic electron model of Arnowitt, Deser, and Misner (ADM), and Mach's Principle.