Since explanationsand their refutationshave not been conclusive, we bring up a new line of thought to the profound discourse that targets to important applications, most notably to keep satellites on orbits. We maintain that the EM drive, like any other propulsion engine, does convert its propellant to expellant, but its exhaust has escaped both experimental detection andattention.

Thrust without exhaust is of course impossible. Namely, for every action there has to be an equal and opposite reaction. Thisentails that a rocket canforwards only by directing backwards a force of equal magnitude. Yet, certain resonant cavities, when fueled withdeliver thrust without apparent exhaust.The thrust has been detected independentlybut there is no consensus about its origin. Possible side-effects have been pointed out, and hence certain experiments have been inconclusive about the thrust.Also credibility of some earlier experimental results has been recently reconsidered in relation to instrumental precision.

10. M. Tajmar and G. Fiedler, “ Direct Thrust Measurements of an EmDrive and Evaluation of Possible Side-Effects ,” in American Institute of Aeronautics and Astronautics conference in Orlando ( Florida , ).

10. M. Tajmar and G. Fiedler, “ Direct Thrust Measurements of an EmDrive and Evaluation of Possible Side-Effects ,” in American Institute of Aeronautics and Astronautics conference in Orlando ( Florida , ).

Our simple assertion prompts theoretical questions and practical concerns. In the following we will address some of the most burning ones.

We infer that the EM drive expels photons in pairs where the two co-propagate with 180 degree phase difference. These composite bosons have no net electromagnetic field, and hence they do not reflect back from the resonator’s metal walls, but escape to surroundings. The paired-photon efflux carries momentum, and hence the cavity experiences an equal but opposite reaction. Thus, we claim that the thrust of an EM drive is the action due to the paired-photon efflux.

Also whenattain thermodynamic balance with matter in the cavity, their number is changing, but thethemselves do not vanish for nothing at absorption to the walls and they do not emerge from nothing at emission from atoms constituting the walls. Put differently,when manipulatingas virtual particles, has been subject to reservations, because its follows from perturbation theory.Instead, the old atomistic tenet makes sense to us by regarding the quanta of light as indivisible and indestructible basic building blocks of nature.

We begin by asking: Is there any other phenomenon, besides that demonstrated with the EM drive, whereas carriers of theforce, are ‘fed in’ but nothing seems to be ‘coming out’? Yes, when coherent rays of light interfere, a diffraction pattern emerges with bright and dark bands – and at a dark band we see nothing (Fig.). We see no light when twocombine with opposite phases. Theirfields cancel perfectly, but that does not mean that thethemselves would have vanished for nothing.

At this point it is of interest to recall that Euler characterized any kind of action by a scalar that integrates projection of the signed curvature along the whole curve with a normal vector that characterizes the surrounding curvature, explicitly, that of the free space. The scalar, known as the geodesic curvature, is proportional to the mass. It is obviously zero for the symmetricalof light quantum.

By the same token for two photons that co-propagate in 180 degrees out of phase the sum of signed curvatures at any point along the wave vanishes, and hence the pair does not exert electromagnetic effects. Since the photon pair without net polarization does not couple to charges, it will easily escape detection, but still carries energy E over its period t as well as momentum p on its wavelength x that relate to each other as E = pc via the speed of light c = x / t . Therefore, we claim that the EM drive consumes free energy in the form of propellant electromagnetic fields by pairing photons with opposite phases to non-polarized expellant.

Geometry at any point along an action can be recapped by signed curvature. The quantity relates to a force. This is familiar, e.g., from the theorem of Gauss and Bonnet. For example, a highly curvedi.e., having a short wavelength is able to force electrons free from a metal surface.Conversely, thewill adapt its curvature, i.e., frequency to match the surrounding energy density embodied in other quantized actions. This change in the photon’s interdependent attributes of energy and time manifests itself, for instance, so that an increasing gravitational potential gradient introduces blue shifts and conversely a decreasing gradient causes red shifts.

The quantum of light is a quantum of action whose unit Js tells us that theis physical, not virtual. The light quantum measures up to Planck’s constantso that the product of photon’s energyand periodattribute remains invariant.The same relation for the momentumon its wavelengthunderlines that the quantum of action is a geometric notion. Theis the elementary action in the form of an openthat carries momentum on its wavelength (Fig.).

Our conjecture means that the EM drive converts the microwave-band photon propellant to the paired-photon expellant. Thus, one might wonder: How does the transformation from photons to photons consume free energy which is invariably needed to do work? To answer we will first address: What is the photon?

Newton thought that matter and light are not fundamentally different from each other.This holistic view has been recently reconciled by presenting particles in terms of quantized actions in agreement with measurements.Thus, our explanation for the thrust is not in an obvious conflict with observations, and hence it is worth further questioning.

Considering the vacuum as physical as we maintain, one might question: Where have all thethat embody the space come from? We argue that the space emerges from matterby reminding that when particles annihilate with their antiparticles, onlywill emerge. For example, when an electron of massannihilates with a positron, it is easy to detect twothat emerge in propagation in opposite directions each with energyaccording to the mass-energy equivalence, but it is easy to miss additionalthat emerge in vacuum pairwise without netand without net momentum. Also in other changes of state, thesepairs easily escape detection when absorbed or emitted. Conversely, particles and their antiparticles will materialize pairwise from mere

Moreover, we recognize that our proposal of the physical vacuum parallels the theory of de Brogliewhere the vibrating particle associates with a spatially extended, particle centered pilotThis view of the vacuum, just as ours, rationalizes numerous quantum mechanical phenomena without conceptual conundrums.

We reason that when the pairedare understood to embody the vacuum, its dielectric characteristics permittivity ε, permeabilityand impedance= √/εnaturally relate to light via= 1/(ε). Already earlier it has been understood that bothand gravitational potentials decay inversely with distance, i.e., as 1/, when both are communicated by thethat embody space.By the same token, it has been realized earlier that, εandare not fundamental constants, but observable parameters of the quantum vacuum which has been portrayed in the form of continuously appearing and disappearing fermion pairs.The ephemeral fermion pair is assumed to result from fusion of two virtualto ensure most notably the total neutrality of the vacuum. Our conjecture of the vacuum as a physical substance embodied by the pairedresembles these models, but we see no compelling reason to account for the vacuum’sproperties by the transient appearance of paired charges. Instead we reason that when a charge is introduced in the vacuum, a force will appear and move the twoapart from the out-of-phase relation. This phase shift will manifest itself as anfield around the charge. Thus, it is no mystery, for instance, from where theof thefield will emerge all of a sudden when an atom ionizes. They have been around all the time, but in the out-of-phase configuration that exhibits itself only as energy density.

We agree the vacuum is not a transfer medium forinstead we maintain that it is made ofWhen thewith out-of-phaseco-propagate in pairs, the space is dark as observed. This out-of-phaserelation, as theminimum configuration, is the natural form of the background energy density. It is no quirk of cosmos the vacuum’s energy density, on the order of nJ/m, closely matches the average energy density of matter within radiusof the Universe, whereis theand the ageis 13.8 billion years.The equality signifies that the photon-embodied vacuum and all matter coevolve by maintaining thermodynamic balance. Therefore we expect that the paired-photon energy density spectrum parallels that of the black-body spectrum of cosmic background radiation.

Our claim that the EM drive expels pairedin the same way as a heat engine exhausts thermalentails that the vacuum, as the ultimate dump, comprises ofThus, one might ask: How could the pairedembody the vacuum, because luminiferous etherhas been abandoned since the negative outcome of Michelson–Morley experiment?

V. WHAT IS GRAVITY? Section: Choose Top of page ABSTRACT I.INTRODUCTION II.THE CONJECTURE III.WHAT IS THE PHOTON? IV.WHAT IS THE VACUUM? V.WHAT IS GRAVITY? << VI.WHAT IS INERTIA? VII.HOW TO GUIDE IMPERCEP... VIII.DISCUSSION REFERENCES CITING ARTICLES

Acceleration due to the proposed paired-photon efflux from the EM drive implies by the equivalence principle that the paired photons are also dissipated when a body is falling down. However, gravity is not described as a dissipative phenomenon either in elementary textbooks or in expanded editions that model curved spacetime with Riemann metric. Since the contemporary comprehension about gravity accounts remarkably well for numerous, if not for all observations, one might ask: What for is a ‘new’ dissipative theory of gravity needed?

F equals the change in momentum p, i.e., F = d t p = d t m v = m a + v d t m (2) where the second term, albeit often omitted from the textbooks and also from advanced writings, represents the thrust, i.e., the change in mass d t m multiplied with velocity v. When d t p = 0, the reaction is equal and opposite to the action, i.e., –vd t m = ma. In other words, no new theory is either proposed or required, but we emphasize the full import of Newton’s statement. We agree, nothing new is needed, but Newton’s second law ought to be held for its full value. The law states that the forceequals the change in momentum, i.e.,where the second term, albeit often omitted from the textbooks and also from advanced writings, represents the thrust, i.e., the change in massmultiplied with velocity. When= 0, the reaction is equal and opposite to the action, i.e., –. In other words, no new theory is either proposed or required, but we emphasize the full import of Newton’s statement.

v, change in kinetic energy K follows from the change in momentum 40–43 40. P.-L.M. De Maupertuis, “ Accord de différentes lois de la nature qui avaient jusqu’ici paru incompatibles ,” Mém. Ac. Sc. Paris 1744, 417– 427 . 41. P.-L.M. De Maupertuis, “ Les loix du mouvement et du repos déduites d’un principe metaphysique ,” Hist. Acad. Roy. Sci. Belleslett. 267– 294 (1746). In the light of time ,” Proc. R. Soc. A 465, 1173– 1198 (2009). 42. P. Tuisku, T.K. Pernu, and A. Annila, “,” Proc. R. Soc. A, 1173–(2009). https://doi.org/10.1098/rspa.2008.0494 The substance of gravity ,” Physics Essays 28, 208– 218 (2015). 43. A. Annila, “,” Physics Essays, 208–(2015). https://doi.org/10.4006/0836-1398-28.2.208 v ⋅ F = v ⋅ d t m v = v ⋅ m a + v 2 d t m d t 2 K ≡ − v ⋅ ∇ U + d t Q (3) where the familiar term ma of acceleration corresponds to energy gradient of the [gravitational] scalar potential U, since d t = v⋅∇, and the change in mass d t m equals via m = E/c2 dissipation d t Q = d t E/n2 to a medium indexed with n = c/v relative to the vacuum whose norm is c2. It is worth emphasizing that the change in mass (Eq. free energy consumption. When multiplying Eq. (2) with, change in kinetic energyfollows from the change in momentumwhere the familiar termofcorresponds to energy gradient of the [gravitational] scalar potential, since∇, and the change in massequals viadissipationto a medium indexed withrelative to the vacuum whose norm is. It is worth emphasizing that the change in mass (Eq. (3) ) does not only count for the difference between the initial and final mass of a rocket with and without propellant but also for dissipation resulting fromconsumption.

photons are contained in interactions. 44 Natural emergence ,” Complexity 17, 44– 47 (2012). 44. T.K. Pernu and A. Annila, “,” Complexity, 44–(2012). https://doi.org/10.1002/cplx.21388 The dissipative change in mass is apparent in nuclear reactions and also noticeable in chemical reactions, but even the tiny change in mass in gravitational changes of state ought to be acknowledged to maintain conceptual consistency. The change can be inferred from the difference between the sum of gravitational potentials of individual bodies and the gravitational potential of the merged bodies. The body is not a mere sum of its material constituents because also theare contained in interactions.

43 The substance of gravity ,” Physics Essays 28, 208– 218 (2015). 43. A. Annila, “,” Physics Essays, 208–(2015). https://doi.org/10.4006/0836-1398-28.2.208 photons must emit from the gravitational potential to the surrounding vacuum, because when the body is lifted back up on its initial height, some fuel is needed, ultimately in the form of absorbed photons, for example, from insolation. Thus, according Eq. accelerates up, via absorption of quanta. Dissipation in the gravitational changes of state is also required by reversibility.When the body falls down on the ground,must emit from the gravitational potential to the surrounding vacuum, because when the body is lifted back up on its initial height, some fuel is needed, ultimately in the form of absorbedfor example, from insolation. Thus, according Eq. (3) when the body falls down, the gravitational potential changes via emission and when the bodyup, via absorption of quanta.

photons, it will grant these quanta to the systemic potentials. This influx of paired quanta will force the bodies to move apart from each other. In particular, the vast Universe generates huge fluxes of paired photons by transforming bound quanta of matter to freely co-propagating photons by stars, black holes and other mechanisms. Remarkably, these propagating density perturbations, known as gravitational waves, were recently captured from a black hole binary merger. 45 et al. , “ (LIGO Scientific Collaboration and Virgo Collaboration) Observation of Gravitational Waves from a Binary Black Hole Merger ,” Phys. Rev. Lett. 116, 061102 (2016). 45. B.P. Abbott, “,” Phys. Rev. Lett., 061102 (2016). https://doi.org/10.1103/PhysRevLett.116.061102 46–49 The redshift-distance relation. IX - Perturbation of the very nearby velocity field by the mass of the Local Group ,” Astrophys. J. 307, 1– 19 (1986). 46. A. Sandage, “,” Astrophys. J., 1–(1986). https://doi.org/10.1086/164387 The local group of galaxies ,” Astron. Astrophys. Rev. 9, 273– 318 (1999). 47. S. Van den Bergh, “,” Astron. Astrophys. Rev., 273–(1999). https://doi.org/10.1007/s001590050019 48. A. Annila, “ Spectrum of cosmic rays reports from the structure of space ,” Advances in Astronomy 135025 (2015). Rotation of galaxies within gravity of the Universe ,” Entropy 18, 191– 205 (2016). 49. A. Annila, “,” Entropy, 191–(2016). https://doi.org/10.3390/e18050191 According to Eqs. (2) and (3) gravity is a force, like any other, whose direction and magnitude express the sign and magnitude of the gravitational energy gradient. When the surrounding vacuum is sparse in energy, it will readily accept the paired quanta when bodies fall toward each other. Conversely, when the surrounding is rich with insolation or with some other energetic flux ofit will grant these quanta to the systemic potentials. This influx of paired quanta will force the bodies to move apart from each other. In particular, the vast Universe generates huge fluxes of pairedby transforming bound quanta of matter to freely co-propagatingby stars, black holes and other mechanisms. Remarkably, these propagating density perturbations, known aswere recently captured from a black hole binary merger.The total flux of pair quanta from numerous sources drives distant galaxies away from us. At a distance about 1.5 Mpc from the Milky Way, the energy influx and efflux balance each other, and hence there is no attraction or repulsion.

23,24,43 All in action ,” Entropy 12, 2333– 2358 (2010). 23. A. Annila, “,” Entropy, 2333–(2010). https://doi.org/10.3390/e12112333 The meaning of mass ,” Int. J. Theor. Math. Phys. 2, 67– 78 (2012). 24. A. Annila, “,” Int. J. Theor. Math. Phys., 67–(2012). https://doi.org/10.5923/j.ijtmp.20120204.03 The substance of gravity ,” Physics Essays 28, 208– 218 (2015). 43. A. Annila, “,” Physics Essays, 208–(2015). https://doi.org/10.4006/0836-1398-28.2.208 50,51 50. J. Lense and H. Thirring, “ Über den Einfluss der Eigenrotation der Zentralkorper auf die Bewegung der Planeten und Monde nach der Einsteinschen Gravitationstheorie ,” Phys. Zeitschr. 19, 156– 163 (1918). Probing Mach’s principle ,” Mon. Not. R. Astron. Soc. 423, 1973– 1977 (2012). 51. A. Annila, “,” Mon. Not. R. Astron. Soc., 1973–(2012). https://doi.org/10.1111/j.1365-2966.2012.21022.x 52 Anomalous Orbital-Energy Changes Observed during Spacecraft Flybys of Earth ,” Phys. Rev. Lett. 100, 091102 (2008). 52. J.D. Anderson, J.K. Campbell, J.E. Ekelund, J. Ellis, and J.F. Jordan, “,” Phys. Rev. Lett., 091102 (2008). https://doi.org/10.1103/PhysRevLett.100.091102 K + U = 0. In the same way as the vacuum’s potential is in dynamic balance with the total energy density of matter in the whole Universe, so is the gravitational potential in dynamic balance with a local energy density of matter bound in the body. The paired-photon embodied gravitational potential can be decomposed to the familiar irrotational scalar potential and to the divergence-free vector potential to account also for rotational effects.Accordingly, the vacuum as the tangible substance couples to a rotating body and hence manifests itself, for example, as the frame-dragging effectand flyby anomaly.When the system has attained thermodynamic balance with its surroundings, then the net flux of force carriers vanishes between the system and its surroundings. At the stationary state, where time variable is redundant, Eq. (3) can be integrated to the familiar virial theorem 2= 0.

Kdt = ∫p⋅vdt = ∫p⋅dx corresponding to the differential equation 31,51,53 Least-action perihelion precession ,” Mon. Not. R. Astron. Soc. 417, 1742– 1746 (2011). 31. M. Koskela and A. Annila, “,” Mon. Not. R. Astron. Soc., 1742–(2011). https://doi.org/10.1111/j.1365-2966.2011.19364.x Probing Mach’s principle ,” Mon. Not. R. Astron. Soc. 423, 1973– 1977 (2012). 51. A. Annila, “,” Mon. Not. R. Astron. Soc., 1973–(2012). https://doi.org/10.1111/j.1365-2966.2012.21022.x Least-time paths of light ,” Mon. Not. R. Astron. Soc. 416, 2944– 2948 (2011). 53. A. Annila, “,” Mon. Not. R. Astron. Soc., 2944–(2011). https://doi.org/10.1111/j.1365-2966.2011.19242.x The integral form ∫2= ∫= ∫corresponding to the differential equation (3) is the principle of least action in its original form by Maupertuis. The least-time imperative says that bodies, just as light according to Fermat’s principle, move along geodesics in agreement with observations.