Friday, June 7, 2013

Star size comparaisons

Interesting video on APOD here

Wednesday, June 5, 2013

Is Gravity Control Propulsion viable? Part 4

From the previous post, we'll follow on from  the general idea of an accelerating quantum vacuum composed of virtual particles interacting with mass which we perceive as gravity (spacetime curvature) and responsible for weight emphasising that this is only a hypothesis that appears to fit General Relativity and may provide an avenue to make new testable quantum predictions on gravity. We haven't ruled out the other possibilites though which are graviton exchange between mass, a combination of quantum vacuum electromagnetic interactions and gravitons, or other interactions via unknown particles. As noted in the previous post, the graviton hypothesis is not a testable model for the foreseeable future and cannot be proved or disproved by experiment so can't be ruled out although is not helpful for our aim for Gravity Control Propulsion (GCP) since we have no control of graviton interactions. We will also look at Gravitoelectromagnetism (vacuum dragging effects). Although there are similarities between Maxwell's field equations and the GR field equations, we'll show later that it appears this cannot be used for GCP. Both classical electromagnetism and gravity operate under Gauss's inverse square law in a three dimensional space, this is where the similarities end, however gravitoelectromagnetism is a useful tool to model the effects of gravity under certain circumstances (such as gravitational waves). Our main aim is to investigate if there is any direct relation between electromagnetism and gravity and understand Nature's mechanism for spacetime curvature due to mass and energy density. Since we are good at manipulating experiments that are electromagnetic based, if there is a relation there would be avenue for GCP related experiments down the track. If there is no relation between electromagnetism and gravity, GCP is in trouble.

The accelerating quantum vacuum is composed of the full spectrum of virtual particles which have their counterpart real particles. Among them there are virtual electrons and positrons (part of the lepton family of particles) both of which have electric charge which means there is avenue for interaction via electromagnetism. We will also need to look at the mix of virtual particles that have zero charge. The diagram below shows the situation quite well for a particle with charge q, velocity v, and the effect of the Lorentz force on this test charge (negative, positive or neutral) due to a magnetic field B coming out of the screen perpendicular to you.

Deflection of a test charge q due to a magnetic field coming out of the screen. Image: Wikipedia.

 Let's have a look at another paper that proposes a similar hypothesis to the previous paper: Does the Quantum Vacuum Fall Near the Earth? The Downward Acceleration of the Quantum Vacuum is Responsible for the Equivalence Principle.

This paper makes several modifications to the previous accelerating quantum vacuum model and although it makes several interesting points it also introduces some highly speculative propositions. In summary the paper proposes:

The downward acceleration of the virtual electrically charged fermion particles of the quantum vacuum is responsible for the Einstein Weak Equivalence Principle and for our perception of 4D space-time curvature near the earth. Since the virtual fermion particles of the quantum vacuum (virtual electrons for example) possess mass, we assume that during their short lifetimes the virtual fermions are in a state of downward acceleration (or free-fall) near the earth. Many of the virtual fermions also possess electrical charge, and are thus capable of interacting electrically with a real test mass, since a test mass is composed of real, electrically charged, fermion particles. The electrical interaction between the downward accelerated virtual fermions with nearby light or matter is responsible for the equivalence of inertial and gravitational mass, and also responsible for our perception of 4D space-time curvature near the earth.

The opposition to acceleration of a test mass by the reverse process is explained to be the cause of inertia. Key point here that is of interest to us is where it is mentioned that the virtual fermions are interacting electrically with mass. It remains to be seen if this hypothesis (ElectroMagnetic Quantum Gravity or EMQG) is correct and if this is the only cause of gravity. The paper does not give a mechanism for the root cause of the downward acceleration of the quantum vacuum however the concept as outlined is enough to explain GR and vacuum dragging effects which is why the model is interesting. We are also moving on from the classical explanation of GR to a quantum model of gravity:

 4D curved Minkowski space-time is now a consequence of the behavior of matter (particles) and energy (photons) under the influence of this (statistical average) downward accelerated ‘flow’ of charged virtual particles of the quantum vacuum. This coordinated ‘accelerated flow’ of the virtual particles can be thought of as a special ‘Fizeau-like vacuum fluid’ that ‘flows’ through all matter near a gravitational field (and also in matter undergoing accelerated motion). Like in the Fizeau experiment (which was performed with a constant velocity water flow) the behavior of photons, clocks, and rulers are now affected by the downward accelerated flow of the virtual particles of the quantum vacuum caused by gravity.
We'll note that the vacuum's net electric charge is neutral and there must be equal numbers of virtual electrons and virtual positrons (anti-electrons) at a given time due to pair creation and annihilation processes. Since these two particles have equal and opposite electrical charge they both react to magnetic fields. Also since this "Fizeau-like vacuum fluid" of virtual particles interacts with normal matter, we can deduce that motion of matter can also influence this "vacuum fluid" which we observe as vacuum dragging effects (gravitomagnetism), normal matter being made of protons and neutrons which are made of charged quarks with our usual cloud of charged electrons surrounding the nucleaus for a standard atom. Also note that this is not a Superfluid Vacuum Theory or Aether model although there are some similarities. 

Real electron and positron curl in opposite directions in a bubble chamber magnetic field. Image:  Britannica
On p8 the paper talks about Hawking radiation for black holes which is of interest to us because here is a special case where the virtual particle and anti-particle pairs do not undergo annihilation at the event horizon and offers further insight on the physics of the quantum vacuum virtual particle field. Vacuum polarisation also shows that our observations of real electron charge is affected by the cloud of virtual positrons of the quantum vacuum that congregate around the electron (also known as charge screening). On p11 the paper goes on to explaim the EMQG model of gravity involving two particle exchange mechanisms:
What is unique about EMQG theory is that gravitation involves both the photon and graviton exchange particles operating at the same time, where now the photon plays a very important role in gravity! In fact, the photon exchange process dominates over the pure gravitational interaction, and is in the most part, responsible for the principle of equivalence of inertial and gravitational mass. The photon particle is also responsible for another property that all matter possesses, the inertial force that acts to give a mass the property of Newtonian inertia.

We cannot verify part of the claim that gravitation involves graviton exchange particles as explained previously (although this is the current accepted norm in Physics) however we can verify photon exchange mechanism in principle. It is mentioned on p13 that there appears to be a deep connection between electromagnetism and gravity because Coulomb's electrical force law: \(F=\frac{KQ_{1}Q_{2}}{r^{2}}\) and Newtonian gravitational force law: \(F=\frac{GM_{1}M_{2}}{r^{2}}\) are similar. Both classical electromagnetism and gravity operate in a three dimensional space where Gauss's inverse square law is applicable. Gravitomagnetism was devised well before GR as a tool to model gravity using the similarities between the two forces. Gravitational waves for eg can be modeled by splitting the gravitomagnetic and gravitoelectric components just like electromagnetic waves can be split into their electric and magnetic field vector components. It appears that no further insight will be gained with this approach since this is a classical tool devised for a classical model of gravity although useful to explain vacuum dragging effects and gravitational waves. We'll keep it as a set for our classical toolbox though. Attempts to discover direct mechanisms to convert electromagnetism to gravity based on the gravitoelectromagnetic field equations are expected to be unsuccessful (see for eg Coupling of Gravitation and Electromagnetism in the Weak Field Approximation).    

Examples of vacuum dragging: Thirring and Thirring-Lense effects. Image: Motion Mountain, Vol 2, p150
On p14 interesting questions are put forward:

Does the graviton particle move in a 4D flat space-time like the photon of QED? Does the graviton exchange process somehow ‘produce’ curvature on an otherwise flat background 4D space-time, when propagating from one mass to another? If the graviton is not responsible, then what is it about mass that is directly capable of producing 4D space-time curvature surrounding the mass? In other words, if the 4D space-time curvature is not caused by the graviton exchanges, then what is the connection between matter and 4D space-time? If you double the mass, you change the amount of space-time curvature. Why?
To our knowledge, these questions remain unanswered. In EMQG, we propose a quantum action based on the quantum vacuum and the existence of graviton particles (that have characteristics very similar to the photon) that resolves these questions. It turns out that the state of acceleration of the quantum vacuum with respect to another test mass represents the quantity of 4D space-time curvature!
 The concept of an accelerating quantum vacuum responsible for 4D spacetime curvature is plausible and also can explain vacuum dragging effects. We will look at some of the problems with the model though and possible modifications required without resorting to new particles (such as the paper's "masseon" particle). Although EMQG also resorts to gravitons for part of their explanation for 4D curvature, it is not clear at this stage if this is a requirement for a successful model since we are unable to question Nature if she is actually using gravitons to mediate gravity. It should be noted that from p16 regarding a derivation for GR, there is a relatively straightforward derivation offered in Motion Mountain Vol 2 Ch 4 "Simple General Relativity: Gravitation, maximum speed and maximum force". Just like Special Relativity is based on maximum speed c in Nature, GR can be derived from the following: There is in Nature a maximum force: \(F\leq\frac{c^{4}}{4G}=3.0\cdot10^{43}N.\) Both maximum speed c and maximum force are properties of the vacuum. It is interesting to note here from Motion Mountain Vol 2 p33:

However, there is at least one system in nature where the speed of sound is indeed a limit speed for energy: the speed of sound is the limit speed for the motion of dislocations in crystalline solids. (We discuss this in detail later on). As a result, the theory of special relativity is also valid for dislocations, provided that the speed of light is replaced everywhere by the speed of sound! Indeed, dislocations obey the Lorentz transformations, show length contraction, and obey the famous energy formula \(E=\gamma mc^{2}\). In all these effects the speed of sound c plays the same role for dislocations as the speed of light plays for general physical systems.
The observation above is interesting for the model of the accelerating quantum vacuum which we are looking at. On p 35, the paper asks the important questions:
Does the general downward acceleration of the virtual particles of the quantum vacuum near a large mass affect the motion of photons propagating within the gravitational field? Or is the deflection of photons truly the result of an actual spacetime geometric curvature (which holds down to the tiniest of distance scales)? 
The answer to this very important question hinges on whether our universe is truly a curved, geometric Minkowski 4D space-time on the smallest of distance scales, or whether curved 4D space-time results merely from the activities of quantum vacuum virtual particles interacting with other real quantum particles. EMQG takes the second view. 
According to postulate 4 (appendix A-11) of EMQG theory, light takes on the same general acceleration as the net statistical average value of quantum vacuum virtual particles, through a ‘Fizeau-like’ scattering process involving many virtual particles. By this we mean that the photons are frequently absorbed and re-emitted by the electrically charged virtual particles, which are (on the average) accelerating towards the center of the large mass. When a virtual particle absorbs the real photon, a new photon is re-emitted after a small time delay in the same general direction as the original photon. This process is called photon scattering (figure 5). We will see that photon scattering is central to the understanding of space-time curvature.

The second view looks plausible however the EMQG model as proposed in the paper with its introduction of several new hypothetical particles other than gravitons to explain how gravity is mediated is highly speculative and doesn't appear to be correct. We'll keep this aside for the time and make a mental note that this part of the model still needs work. The explanation from p39 on photon scattering in a static and accelerated quantum vacuum is interesting. It is feasible that the photon undergoes a time delay between absorption and re-emission between each charged virtual particle it encounters in the quantum vacuum and undergoes a "photon vacuum delay" which gives an average light velocity of 300000 Km/s. It is not clear however if there is a higher "raw light velocity" of the photon between each charged virtual particle, at this stage this cannot be verified (however see the following paper: Does the speed of light depend upon the vacuum?). One can speculate if the density of the charged virtual particles could be reduced somehow in a given volume of the quantum vacuum, this average light velocity could be increased as the number of encounters with charged virtual particles is decreased. The charged virtual particles can be seen as offering resistance to the propagation of the photons. This fits in well with photon scattering processes in materials, Fizeau's moving water experiment mentioned earlier in the paper and the equations of motion of dislocations in crystalline solids mentioned above.  We'll follow on from p44:

We are now in a position to understand the concept of the geodesic proposed by Einstein. The downward acceleration of the virtual electrically charged masseons of the quantum vacuum serves as an effective ‘electromagnetic guide’ for the motion of light (and for test masses) through space and time. This ‘electromagnetic guide’ concept replaces the 4D space-time geodesics that guide matter in motion in relativity. For light, this guiding action is through the electromagnetic scattering process of section 9.5. For matter, the electrically charged virtual particles guide the particles of a mass by the electromagnetic force interaction that results from the relative acceleration. Because the quantum vacuum virtual particle density is quite high, but not infinite (at least about \(10^{90}\) particles \(/m^{3}\), the quantum vacuum acts as a very effective reservoir of energy to guide the motion of light or matter.

If the overall model turns out to be correct and we can devise a method to interfere with the electrical interaction of the vast numbers of falling virtual charged particles with the real, electrically charged matter particles for a test mass then there is an avenue to carry out GCP related experiments. What is interesting here is that although the details in the gravity mediation process is still unclear at this stage, the effect isn't and if the  secondary cause is via electrical interactions we can in principle interact or interfere with the process even if the root cause turns out to be via neutral gravitons which we cannot interact or modify.

At this stage however using the above model (if correct) we can for example rule out the Podkletnov and Tajmar experiments which both rely on rotating superconducting rings. Podkletnov's experiment claimed a 2% weight reduction on a test mass in the center of the ring. The magnetic field generated by the rotating superconducting ring is not preventing the accelerating quantum vacuum charged virtual particles from interacting with the test mass at its center as the field configuration in incorrect. Another experiment by Tajmar was devised to look at gravitomagnetic and gravitoelectric fields is also incorrect. As mentioned previously above, one should not confuse vacuum dragging effects that can be modeled with classical gravitomagnetism with actual real fields in Nature.

Podkletnov's experiment: no weight reduction can be obtained with this configuration.  

Tajmar's experiment: no gravitoelectric and gravitomagnetic fields can be found,
only vacuum dragging effects can be measured.

In Part 5 of these series, we'll look at some of the problems with the EMQG model and modifications required that doesn't rely on hypothetical particles. We also need to deal with the neutral virtual particles that make up the accelerating quantum vacuum and look at some testable predictions that can be verified by experiment.


Update: Interesting post on Backreaction: Quantum gravity phenomenology detecting gravitons