Ning Wu's Gauge Gravity By Dr. Ning Wu, December 14, 2004 American Antigravity Exclusive! Originally entitled "Gravity, Gauge Gravity, and Gravitational Shielding", this new article by Dr. Ning Wu describes many of the cutting-edge concepts linking research in superconductors and gravity modification to a new gauge-theory of his creation. 1. Brilliant History of the Theory of Gravity Gravity is an ancient topic in science, it is one kind of interaction which is known earliest by mankind. In ancient times, human has known the existence of weight. Now, we know that it is the gravity between an object and earth. Gravity exists everywhere in nature, it is met by us most commonly in our everyday life. It is the most familiar interactions to us. But it is the most mysterious and most profound interactions of nature. The study on the theory of gravity propels the civilization forward, promotes the raising and developing of science, embodies the greatest intelligence and most brilliant achievement of mankind. It is one of the key topics of physics. In the seventeenth century, Johannes Kepler found the famous Kepler's law. Later, Issac Newton explains these laws as the result that the gravity between the sun and planet obeys the inverse square law. This study results in the establishment of the great Newton's theory of universal gravitation and Newtonian mechanics, which is one of the greatest milestone in the history of science. Newton's classical theory of gravity can explain the orbital motion of planet in solar system, the motion of the moon around the earth, and tide phenomenon in the earth. Based on Newton's theory of gravity, John Crouch Adams and Urbain Jean Joseph Le Verrier predict the existence and position of Neptune. The discovery of Neptune shortly thereafter was perhaps the most splendid verification of Newton's theory of gravity. Newtonian mechanics and Newton's theory of universal gravitation met with a brilliant series of successes. It is known that Newton's theory is based on the concept of absolute space-time. Though the concept of absolute space-time is consistent with our experience, it is frequently attacked by many philosophers and physicists. Such attacks finally lead to a great revolution of physics: the foundation of the theory of relativity. A new marvelous concept of space-time, which is completely different from our ordinary experience, is established in the theory of relativity. In the general theory of relativity, gravity is treated in a novel manner: it is considered as the geometry of space-time. According to the general theory of relativity, we are living in a curved space-time. The existence of matter determines the curvature of space-time, and the effects of the curved space-time is just the gravity we usually feel. In this point of view, gravity and the electromagnetic force have some essential differences: the essence of gravity is the geometry of space-time, and the gravitational force we feel is only an effect of curved space-time; while the essence of electromagnetic force is a kind of physical interaction force which is transmitted by photon. In other words, the essence of gravity is geometry, while the essence of electromagnetic force is physics. We know that the general theory of relativity meet with a brilliant series of successes: it successfully explain the excess precession of Mercury, deflection of light by the sun and radar echo delay. Now, the application of the theory of relativity is becoming wider and wider, it is the basis ofmodern astrophysics and modern cosmology. 2. Physics or Geometry? In general relativity, a new concept of space-time is established, and gravity is considered to be geometry of space-time, which is the essential distinction between Newton's classical theory of gravity and Einstein's general relativity. It is known that, in Newton's classical theory of gravity, gravity is considered to be a kind of physical interactions, space-time, which is the background that all matters exist and evolve, is always flat, and gravity can not change the structure of space-time. But in general relativity, gravity is no longer considered to be a kind of physical interactions. It is geometry of space-time, or it is a part of the structure of space-time. Gravity and space-time are essentially the same thing. So now, a fundamental issue is raised: Is the essence of gravity geometry of space-time or a kind of physical interactions? 3. Incomplete Revolution One of the greatest revolution in human kind in the twentieth century is the foundation of quantum theory. The quantum hypothesis was first introduced into physics by Max Plank in 1900. Inspired by his quantum hypothesis, Albert Einstein used it to explain the photoelectric effect successfully and Niels Bohr used it to explain the positions of spectral lines of Hydrogen. In 1923, Louis de Broglie proposed the principle of wave-particle duality. In the years 1925-1926, Werner Heisenberg, Max Born, Pascual Jordan and Wolfgang Pauli develop matrix mechanics, and in 1926, Erwin Schroedinger develop wave mechanics. Soon after, relativistic quantum mechanics and quantum field theory are proposed by P.A.M.Dirac, Oskar Klein, Walter Gordan and others. In 1921, H.Weyl introduced the concept of gauge transformation into physics, which is one of the most important concepts in modern physics, though his original theory is not successful. Later, V.Fock, H.Weyl and W.Pauli found that quantum electrodynamics is a gauge invariant theory. In 1954, Yang and Mills proposed non-Abel gauge field theory. This theory was soon applied to elementary particle physics. Unified electroweak theory and quantum chromodynamics are all based on gauge field theory. The predictions of unified electroweak theory have been confirmed in a large number of experiments, and the intermediate gauge bosons W± and Z0 which are predicted by unified electroweak model are also found in experiments. The U(1) part of the unified electroweak model, quantum electrodynamics, now become one of the most accurate and best-tested theories of modern physics. All these achievements of gauge field theories suggest that gauge field theory is a fundamental theory that describes fundamental interactions. Now, it is generally believed that four kinds of fundamental interactions in Nature are all gauge interactions and they can be described by gauge field theory. From theoretical point of view, the principle of local gauge invariance plays a fundamental role in particle's interaction theory. In 1916, Albert Einstein points out that quantum effects must lead to modifications in the theory of general relativity. Soon after the foundation of quantum mechanics, physicists try to found a theory that could describe the quantum behavior of the full gravitational field. In the 70 years attempts, physicists have found many theories based on quantum mechanics that attempt to unify general relativity and quantum mechanics, one is canonical quantum gravity and another is superstring theory. But for quantum field theory, there are different kinds of mathematical infinities that naturally occur in quantum descriptions of fields. These infinities should be removed by the technique of perturbative renormalization. However, the perturbative renormalization does not work for the quantization of Einstein's theory of gravity, especially in canonical quantum gravity. In superstring theory, in order to make perturbative renormalization to work, physicists have to introduce six extra dimensions. But up to now, none of the extra dimensions have been observed. To found a consistent theory that can unify general relativity and quantum mechanics is a long dream for physicists. The "relativity revolution" and the "quantum revolution" are among the greatest successes of twentieth century physics, yet two theories appears to be fundamentally incompatible. General relativity remains a purely classical theory which describes the geometry of space and time as smooth and continuous, on the contrary, quantum mechanics divides everything into discrete quanta. The underlying theoretical incompatibility between two theories arises from the way that they treat the geometry of space and time. This situation makes some physicists still wonder whether quantum theory is a truly fundamental theory of Nature, or just a convenient description of some aspects of the microscopic world. Some physicists even consider the twentieth century as the century of the incomplete revolution. To set up a consistent quantum theory of gravity is considered to be the last challenge of quantum theory. In other words, combining general relativity with quantum mechanics is considered to be the last hurdle to be overcome in the "quantum revolution". 4. Inspiration: The Idea of Unification of Interactions There are two way to establish the theory of quantum gravity. One way is to quantize general relativity. In this case, the starting point of the theory is general relativity. Another way is to pursue the idea of the unification of fundamental interactions. The idea of the unification of fundamental interactions was first proposed by Albert Einstein, but the real unification of fundamental interactions is accomplished in the frame work of quantum field theory. Quantum field theory is one of the most splendid achievement in the twentieth century physics. It is a powerful theory to describe fundamental interactions of elementary particles. Now, it is the framework for the realization of idea of the unification of fundamental interactions. We know that, there are four kinds of fundamental interactions: strong interactions, electromagnetic interactions, weak interactions and gravitational interactions. According general relativity, gravity is geometry of space-time, which is essentially different from other three kinds of fundamental interaction. In this point of view, it is difficult to unify gravity with other fundamental interactions, for they have different nature. But according to the idea of the grand unification, all fundamental interactions should have the same origin and the same essence. We know that strong interactions, electromagnetic interactions and weak interactions are all gauge interactions, gauge is their common essence, and the sound theory to describe them is gauge field theory. The great successes of gauge field theory enlighten us that the essence of gravity should also be gauge. Therefore, to establish quantum gauge theory of gravity is a direct inspiration from the idea of grand unification. The essence of gauge is to reveal the essential and positive connection among conservation, symmetry and interactions. Grasping this connection, we will grasp the crux of the interaction theory, which is to determine the law of interactions through conservation and symmetry. Therefore, the key to the work of the establishment of quantum gauge theory of gravity is to determine the symmetry and the conserved charge of gravitational interactions. According to gauge principle, the source of a interaction is just the conserved charge of the related symmetry of that interaction. It is know that the source of gravity is energy-momentum, and energy-momentum is the conserved charge of the symmetry of space-time translation. Therefore, the symmetry of gravity is space-time translation, and the corresponding conserved charge is energy-momentum. Then applying the gauge principle, we can establish a consistent quantum gauge theory of gravity, which is the first perturbatively renormalizable quantum theory of gravity in 4-dimensional Minkowski space-time. 5. Physics-Geometry Duality The essential distinction between quantum gauge theory of gravity and general relativity is that they have different transcendental principle. The transcendental principles of general relativity are equivalence principle and the the principle of general covariance, while the transcendental principle of quantum gauge theory of gravity is gauge principle, which states that the source of interactions is just the conserved charge of the corresponding global symmetry, gauge interactions need to be introduced when localize the global symmetry, and laws of gauge interactions are determined by local gauge symmetry. Different transcendental principles lead to that general relativity and quantum gauge theory of gravity have completely different mathematical expressions. Another essential distinction between quantum gauge theory of gravity and general relativity is that they have different concepts on space-time and gravity. In general relativity, gravity is considered to be geometry of space-time, and gravitational force is just an effect of curved space-time. But in quantum gauge theory of gravity, gravitational force is considered to be a kind of physical interactions, and the concept of curved space-time is only a convenient and equivalent description of the classical effects of gravitational interactions. Transcendental principles of the theory and basic concepts on space-time and gravity are key important for us to know the essence of gravity and to establish the basic theory of gravity. So, what is the essence of gravity? First, Issac Newton consider that gravity is a kind of physical interactions which have nothing to do with the structure of space-time. Later, in general relativity, Albert Einstein consider that gravity is the geometry of space-time. Now, in quantum gauge theory of gravity, the essence of gravity is considered to a kind of physical interactions again. This situation lets us remember the history of our understanding on the essence of light. First, Issac Newton consider that light consist of particles. Soon after, Christiaan Huygens argues that the essence of light is a kind of wave. Later, Albert Einstein consider that light consists of quantum which is known as photon. In quantum mechanics, de Broglie propose that concept of particle-wave duality. Inspiration from this history on light, in quantum gauge theory of gravity, the concept of physics-geometry duality is proposed. That is, gravity is a kind of physical interactions which has the characteristics of geometry; it is also a geometry of space-time which is essentially a kind of physical interactions. Because of physics-geometry duality, we need first select a picture of gravity when we perform any theoretical calculations in quantum gauge theory of gravity. There are mainly two pictures of gravity: one is physics picture, and another is geometry picture. The basic of gauge theory of gravity is the physics picture, and quantum gauge theory of gravity is established in the physics picture of gravity. As we have states above, in the physics picture of gravity, space-time is always flat, and gravitational force is transmitted by gravitational gauge field which exists in the flat space-time. However, we can also set up the geometry picture of gauge theory of gravity. That is, by performing a simple transformation, we can transform gauge theory of gravity from physics picture to geometry picture. When we go into the geometry picture of gravity, we need to define a equivalent "space-time metric", which is the equivalent of the metric tensor in the general relativity. This equivalent "space-time metric tensor" is defined in terms of gravitational gauge field. So, now things are very clear: gravity is put into the structure of space-time, "space-time" becomes "curved", and in this equivalent "curved space-time", gravity outwardly disappears. We find that, based on this equivalent "space-time metric tensor", we can formulate gauge theory of gravity again, which is just the gauge theory of gravity in geometry picture. In geometry picture, all mathematical formula are expressed in term of the equivalent space-time metric tensor", and gravitational gauge field does not outwardly appear in any mathematical expressions. It means that all effects of gravitational interactions are contained in the structure of the "curved space-time". An important result of this transformation is that the field equation of gravitational gauge field in physics picture is changed into the Einstein's field equation in geometry picture. In fact, after transforming into geometry picture, gauge theory of gravity can give out all basic physical equations in general relativity. In other words, after transforming into geometry picture, gauge theory of gravity can "return" to general relativity. Here, the word "return" only means that it can mathematically return to general relativity and reproduce all physical results in general relativity. In this meaning, gauge theory of gravity can be considered to a development of general relativity and a consistent unification of general relativity and quantum theory. General relativity can only describe classical motion of an object in gravity, but gauge theory of gravity can describe not only the classical motion of an object in gravity, but also evolution of a quantum gravitational field or a quantum states in gravity. For classical problems, gauge theory of gravity can "return" to general relativity after a transformation into geometry picture. But, gauge theory of gravity can not physically return to general relativity, for they have different transcendental principles and different concepts on gravity. For quantum problems, especially when there is quantum gravitational gauge field, the geometry picture is not valid and the equivalent "curved space-time" can not be correctly erected. 6. Violation of Weak Equivalence Principle As we have stated above, the transcendental principle of gauge theory of gravity is gauge principle, and and transcendental principles of general relativity is equivalence principle and the principle of general covariance. Because gauge theory of gravity can "return" to general relativity after transforming into geometry picture, we have two different way to establish general relativity. One way is the Einstein's way, that is to start from the equivalence principle and the principle of general covariance. Another way is to start from gauge principle. But, gauge principle is not equivalent to the equivalence principle and the principle of general covariance. So, what should be the transcendental principle of the theory of gravity? For classical problems, equivalence principle and gauge principle can give out the same physical results. So, in order to answer the question that which one should be the transcendental principle of the theory of gravity, we need to study quantum problems. When we study quantum problems, we find that the spirit of equivalence principle is violated, while the spirit of gauge principle is conserved. The original expressions of the equivalence principle is that the gravitational mass of matter is equivalent to its inertial mass. Therefore, the mass term in Newton's equation of motion can be cancelled, and the orbit of a point particle in gravity does not depend on its mass. So, even if the initial position and initial velocity are the same, no matter how weight they are, these particles will have completely the same orbit. (Now, this expression is call weak equivalence principle.) It is this property that lead to the idea of the geometrization of gravity. But, this property is violated in quantum theory. The mass parameter in the Schrodinger equation with gravity potential can not be cancelled in any case. Therefore, quantum states in gravitational field and its evolution are doomed to be dependent on its mass. In other words, the evolution of a quantum state in gravitational field depends on the mass of the particle, which violates weak equivalence principle. Or say that it violates the original spirit of the equivalence principle. With regard to the above contradiction between quantum theory and weak equivalence principle, there are two two distinct point of view striking opposite to each other. One states that weak equivalence principle holds in all cases, while Schrodinger equation is not applicable to the gravity dominated system. Another states that Schrodinger equation is applicable to the gravity dominated system also, but weak equivalence principle is violated in a quantum system. Experiments find that the latter viewpoint is correct. In 1970s, R. Covella, A.W.Overhauser and S.A.Werner performed the famous gravitational phase experiment, which is now called as COW experiment. Experimental result is highly consistent with the prediction given by the corresponding Schrodinger equation. COW experiments clearly manifest that Schrodinger equation holds for the gravity dominated system, and weak equivalence principle does not hold for a quantum system. COW experiment is an important experiment which help us to understand the essence of gravity and to determine the transcendental principles of a fundamental theory of gravity. 7. Miraculous Gravitational Shielding In 1992, E.E.Podkletnov found that a special prepared ceramic superconductor with composite structure can reveal a weak gravitational shielding effect. This miraculous effect causes much trouble to the traditional theory of gravity. In Newton's classical theory of gravity, gravitational field can pass through any object without any abnormal attenuation of its strength. In other words, the magnitude of the gravitational force between two objects can not be changed by the third object between. For example, we have two balls with 1 kilogram weight each and the distance between them is 1 meter. Then Newton's theory of gravity tells us that the gravitational force between these two balls is 6.67 ´ 10-11 N, no matter that the space between them is vacuum or filled with any material. It means that gravity can not be shielded in Newton's classical theory of gravity. In general relativity, gravity can not be shielded yet, for gravity is the structure of space-time, and space-time can not be shielded. In general relativity, gravity is represented by space-time metric tensor. According to Einstein's field equation, metric tensor is determined by the energy-momentum tensor of matter fields existed in space-time. Because gravitational coupling constant is extreme small, only huge amount of matter can obviously change space-time metric tensor. If we want to obviously change the earth's gravitational field, we need an huge object whose mass is close to the earth's mass, which is impossible for human beings. That we can not obviously change earth's gravitational field means that we can not shield earth's gravitational field, for shielding itself needs obviously change. Similar argument is still valid in Newton's theory of gravity. But, there may exist the phenomenon of gravitational shielding in quantum gauge theory of gravity. It is known that, in quantum theory, all interactions are transmitted by quantum fields. For example, electromagnetic force is transmitted by electromagnetic field, strong interaction force is transmitted by gluon field. We known that some quantum fields have masses and some are massless. If a quantum field has mass, the mass term will lead to exponential attenuation of the force transmitted by that quantum field, so that force will be rapidly attenuated to zero in a short distance. In this case, that kind of interaction can not be transmitted to distant place. For example, the mass of p meson is 139 MeV, the range of the nuclear force transmitted by it is only 1.4 ´ 10-15 meter. Only when the quantum fields is massless, the corresponding interaction can be propagated to an infinite distance. So, the electromagnetic field and gravitational gauge field are all massless field. Because gravitational field is massless, it can propagate to cosmologically interesting distance and dominates the evolution of the universe. The mass of a quantum field is not immutable. It is known that interactions can change the physical mass of a field and can make massless field obtain a non-zero mass. The famous Higgs mechanism is the mechanism that make gauge field, which is originally massless, obtain a non-zero mass. In unified electroweak theory, intermediate gauge bosons W± and Z0 obtain a large mass term through Higgs mechanism, which the weak force transmitted by W± and Z0 can only propagate about 10-18 meter. If Higgs Mechanism happens on electromagnetic field, electromagnetic field can obtain a small mass term which make electromagnetic filed attenuate to zero in a short distance. The macroeffect of this phenomenon is just that electromagnetic shielding. In ordinary case, this mechanism does not happen, so electric field and magnetic field can propagate to a long distance. But, in some special matters, the Higgs mechanism of electromagnetic field does happen. The most famous example is superconductor. It is known that, when the phase transition from ordinary phase to superconductor phase happens, the spontaneous symmetry breaking is happened in the local space where there is superconductor. This spontaneous symmetry breaking initiate Higgs mechanism which make electromagnetic field obtain a small mass term. Though the mass obtained from this mechanism is small, it can make electromagnetic field attenuate to zero in a short distance of about 10-8 meter. Therefore, in vacuum, the mass of electromagnetic field is zero, so it can propagate infinitely. But when electromagnetic field goes into superconductor, it obtains a mass term and attenuates rapidly. This is electromagnetic shielding in superconductor. The electromagnetic shielding in superconductor give us inspiration that, so long as we can make a force field which can transmit a long-range force obtain a mass term in a local space, we can shield it. If we can make gravitational field obtain a mass term in some local space, the gravitational field will attenuate exponentially when propagating in that region. Applying this method, we can shield gravitational field, which is the gravitational shielding mechanism in quantum gauge theory of gravity. It is interesting to find that superconductor can not only shield electromagnetic field, but also shield gravitational field. But there is a little difference between these two shielding. This difference originates from the fact that the manner of their coupling with matter field is different: electromagnetic field couples with matter fields directly, but gravitational field couples with matter fields through derivative operator. Derivative coupling means that gravitational field can only feel space and time variations of matter fields, not matter fields themselves. When there is spontaneous symmetry breaking, homogeneous superconductor can make electromagnetic field obtain a mass term and lead to electromagnetic shielding. But, it can not make gravitational field obtain a mass term, and therefore can not lead to gravitational shielding. But nonhomogeneous superconductor can make gravitational field obtain a mass term, which will speed the attenuation of gravitational field and lead to gravitational shielding. According to this mechanism, only nonhomogeneous superconductor can shield gravitational field, ordinary homogeneous superconductor can not shield gravitational field. The weak gravitational shielding effect found by E.E.Podkletnov maybe caused by this mechanism. Some other experiments found that superconductor can not shield gravitational field, which may caused by using ordinary homogeneous superconductor. Gravitational shielding effect has great theoretical significance. As we have said above, there are two distinct point of view of the essence of gravity: One considers that gravity is geometry of space, and another considers that gravity is a kind of physical interactions. In the geometry picture, gravity can not be shielded. In fact, in any classical theory of gravity, gravitational force of the earth can not be obviously shielded. The observed gravitational shielding can only be explained by the attenuation of gravitational field in propagating, whose mechanism essentially originate from quantum effect. In this mechanism, gravity should be considered to be a kind of physical interactions which is transmitted by gravitational field. So, the great theoretical significance of the gravitational shielding effect is that it directly manifests the physics origin of gravitational interactions. Besides, it is the first observed quantum effect of gravitational interactions, for it can only be explained by quantum theory of gravity. As we state above, the essence of gravitational shielding effect is that the interaction between quantum gravitational field and nonhomogeneous quantum vacuum states gives a small mass term to gravitational field and leads to gravitational shielding effect, which is essentially a quantum effect. Only from the point of view of quantum theory of gravity can gravity be shielded. Gravitational shielding effect also has momentous practical significance. Obviously, if gravity can be shielded, it will cause a revolution of the style of transportation, especially it will initiate a revolutionary change to future's space craft. If we can grasp the technique of gravitational shielding, we can locally shield earth's gravitational field, then we can walk above the cloud, we can walk in the sky freely like an angel, we can walk into outer space, we can walk to the moon, to the Mars, ¼. Gravitational shielding can make space travel much easier, more economic, more safety and more comfortable, which will promote developing and utilizing of outer space. Living space of human beings can be extended to outer space in future. No doubt it will give rise to a deeply change of human society. Because of gravitational shielding, a glorious future is coming. However, the present gravitational shielding effect is very weak, and still many research group can not repeat Podkletnov's experiment. In order to repeat Podkletnov's experiment, increase shielding effect and make it applicable to space travel, many challenging and pioneering work need to do. We have enough reason to believe that the study on gravitational shielding will be extensively carried out in the future, and the whole human society will benefit much from it. Contact Info Dr. Ning Wu Institute of High Energy Physics, P.O.Box 918-1, Beijing 100039, P.R.China Email address: wuning@mail.ihep.ac.cn

Related Information Contact Information - Dr. Ning Wu can be contacted at the following organization: Institute of High Energy Physics, P.O.Box 918-1, Beijing 100039, P.R.China Email Contact - To send Dr. Wu an email about this remarkable theory! Click Here Download PDF - To download this article in compressed PDF format, use the link below. Click Here Related Document: "Gravitational Shielding Effects in Gauge Theory of Gravity" Click Here Related Document: "A Possibility of Gravitational Force Shielding by Superconductor" Click Here Gravity Shielding Gravity Waves - Check out our newest page on Podkletnov, Li, and others in this breakthrough science! click here Podkletnov Grav/Shield- Our original page on gravity-shielding work in superconductors. click here PopMech - "NASA's Antigravity Machine" by Jim Wilson contains a pre-testing overview of the Nasa replication. (Pop. Mechanics, 12/1997) click here Wired Mag - "Breaking the Law of Gravity" by Charles Platt was an in-depth breakthrough article about superconductive gravity shielding. (Wired Magazine, 03/1998) click here