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#2480 by WarpTech on 26 Oct, 2017 19:39
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Let's re-capitulate the versions of Mach's Principle listed by Samuel and Bondi:
Mach0: The universe, as represented by the average motion of distant galaxies, does not appear to rotate relative to local inertial frames.
Goedel's metric violates this
Mach7: If you take away all matter, there is no more space.
This is violated by all vacuum solutions, and is particularly violated by Ozsváth and Schücking's because it contains no singularities behind which matter can hide
PS: The discussion above is purely within General Relativity. When you talk about your EM ZPF you are discussing a different theory. In General Relativity there is no such thing as Quantum Vacuum. Quantum Mechanics is separate from General Relativity. If you consider the EM ZPF to have a ground state with non-zero-density or a fluctuating density around this ground state, then according to General Relativity, the EM ZPF is not a vacuum. According to General Relativity a vacuum has constant zero density. This is what is meant by Ozsváth and Schücking's solution: it is a solution for a universe with constant zero density.
"constant zero density", are you referring to Mass Density or Energy Density?
An EM field has zero rest mass, which could be interpreted as zero "mass" density, but it has non-zero energy density. The QV has non-zero Spectral Energy Density and we know this to be true "everywhere". So there is no "vacuum solution" that agrees with QED.
It seems to be, both GR and Mach's principle are flawed and outdated, given what we know about the QV. If there is no hope to modify GR without calling it a "different theory", then I have to admit, I profess to disagree with GR. "Nothing can't be curved!"
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#2481 by Rodal on 26 Oct, 2017 19:49
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All types of energy gravitate (electromagnetic energy gravitates: energy density, Maxwell stress tensor and Poynting vector are all in the stress-energy tensor and hence they count as E/c^2 , as pressure also does). The only energy not included is the gravitational potential energy.
"constant zero density", are you referring to Mass Density or Energy Density?
An EM field has zero rest mass, which could be interpreted as zero "mass" density, but it has non-zero energy density. The QV has non-zero Spectral Energy Density and we know this to be true "everywhere". So there is no "vacuum solution" that agrees with QED.
It seems to be, both GR and Mach's principle are flawed and outdated, given what we know about the QV. If there is no hope to modify GR without calling it a "different theory", then I have to admit, I profess to disagree with GR. "Nothing can't be curved!"
Yes, given what is known about Quantum Mechanics a unified theory with GR is necessary to understand the Big Bang, what is inside Black Holes, probably to understand Dark Energy and many other things
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#2482 by TheTraveller on 27 Oct, 2017 00:32
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I am guessing you haven't studied calculus, that is the incorrect way to take a derivative.Kinetic energy is not frame invariant, it is a function of velocity which is obviously not frame invariant. It is also not a linear function of velocity, so differences in kinetic energy also cannot be frame invariant.
The change in KE and work done can be frame invarient as follows.
Acceleration causes a change in velocity, which is frame invarient. All frames observe the same change in velocity, the same dV.
Using the dV, the change in KE can be calculated as dKE = m dV^2 / 2. Work done is then equal to dKE.
The correct answer is dKe/dV = m*v, which is a function of velocity, not difference in velocity, so by the third or fourth different method, it is still not frame invariant.
Please note, that at this point further "proofs" from you are pointless unless you directly point out something wrong with all of the proofs I have provided. My proofs include directly calculating kinetic energy using the equation for kinetic energy, and I also linked you to a first principles derivation of this equation.
Hi Meberbs,
Change in velocity = final velocity after acceleration - initial velocity before acceleration is frame invarient. Agree?
Therefore the work done to cause the velocity change and associated KE change of the accelerated mass is J = m dV^2 / 2, which is frame invarient. -
#2483 by dustinthewind on 27 Oct, 2017 02:07
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What about r = 0, that is to say R = Rs ?
It has been shown (reference) that a change of coordinates can eliminate this "true" singularity, because such singularity is not really "true" it is caused by a wrong choice of local topology.
The "magical" change of variable is to take:
r = Rs (1 + Log ch ρ)
...
Unfortunately they (http://www.jp-petit.org/papers/cosmo/2015-ModPhysLettA.pdf) don't achieve this simply by a "magical" change in variables in a conventional metric cosmology.
There is a heavy price to pay.
It is not just topology of conventional spacetime manifolds that others were unable to see.
Instead the way they manage to eliminate the singularity is by using a very unconventional "Janus" Cosmological Model of the universe composed by positive and negative energy (and mass if they own) particles, respectively described separate metrics g(+)µν and g(−)µν , solutions of a coupled field equation system. https://forum.nasaspaceflight.com/index.php?topic=43501.msg1709505#msg1709505
Two distincts things there.
The authors indeed propose both a cosmological model involving negative mass; and a black hole model where the central singularity is eliminated with a change of variable. Both models are of course compatible (i.e. when used together) but one or the other can also exist without the other one being true.
Yes, the "diabolo topology" strongly militates for a connection of two distinct spacetimes. But it could also describe the connection of two distant regions of the same spacetime. Although the second proposition may seem problematic at first due to the lack of any observable white fountain in the universe, this is not such a problem anymore when the process is considered as ephemeral, as radial frame-dragging implies a finite (and quite fast) process.
Both the cancellation of the central singularity (using the proper change of variable) and the finite-time transit (due to radial frame-dragging) are disconnected from the Janus cosmological model roots and could still be used in other frameworks (such as the brane cosmology you and others cited many times in these threads).
So again, the change of variable can be particularly interpreted as a mass inversion process in a finite time transit through an orbifold acting as a one-way membrane triggering CPT symmetry between two spacetimes in the framework of the Janus cosmological model, after Sakharov-Souriau-Petit. But such black hole model with no central singularity is not restricted to this particular cosmological model. They just fit well together and the paper you and I are referring to (Cancellation of the central singularity of the Schwarzschild solution with natural mass inversion process indeed makes use of the two models in an interweaved way, as implied by its title).QuoteTheir model implies injection of negative energy (and mass if they own) particles in spacetime, considered as a manifold plus two metrics . They also had to assume that particles of opposite masses do not interact neither by electromagnetic forces nor strong or weak forces.
This is because gravity is different in essence (Hinted already. But you do not agree. Although there may be different interpretations?). Gravity is spacetime curvature. Gravity is not mediated by particles following geodesics of spacetime, like photons. Consider models of gravity where one (not two!) manifold includes several metrics. Not a problem for mathematicians. Let's say there are only two metrics: in physics this is a particular form of bimetric gravity (also called "bigravity"). Negative energy photons and positive energy photons follow null-geodesics of their own metric, that preclude any electromagnetic interaction. This is different for gravity. Being part of the same universe, but not the same metric, positive and negative masses induce spacetime curvature that is felt by both species:
There you can understand that a mass is not intrinsically "negative" as a mass always induces a positive curvature in its own metric. The negative nature of gravity is also a relativity concept, as a mass is felt as being "negative" only from the point of view of an observer in the opposite metric (a hypothetical red observer made of "negative" mass in the image above would feel the blue Earth, although invisible, as being a concentration of negative mass, from his own point of view). This phenomenon can be described as "conjugate curvatures" or "conjugate geometries": Positive mass here, induces negative mass there.
But the 2D didactic image of a flat bedsheet or wire mesh being distorted is incomplete, as geodesics are different when a positive or a negative curvature is considered. Positive mass locally induces positive curvature in spacetime, i.e. where the sum of angles of a triangle > 180°); although negative mass locally induces negative curvature in spacetime where the sum of angles of a triangle < 180° in such a hyperbolic space the shape of a horse saddle:
So keeping in mind that in the Janus model, positive mass there induces negative curvature in the opposite metric, therefore some matter (in yellow below) flowing from one metric to the other (in purple) through a bridge located at the center of a destabilized neutron star (Schwarzschild black hole) can be represented in this 2D animation showing the evolution of conjugate curvatures through the process:
More explanations there to prevent this message from becoming too long.
Again, you see a mass is never intrinsically negative. Topology produces only apparent and relative negative curvatures. Instead of introducing "negative mass in cosmology" the Janus model explains the nature of negative spacetime curvature as being a relative concept between two metrics, so everything follows from topology. And is still described by field equations.QuoteThere is no physical evidence for such a cosmological unconventional model composed by positive and negative energy (and mass if they own) particles, respectively described separate metrics g(+)µν and g(−)µν
So, they replace one problem deep inside the event horizon of a black hole (the singularity at r=0) with another problem (2 separate metrics, and existence of negative energy) for the whole naked Universe, -which we can see- for which we have no cosmological experimental evidence of existence (aside from a very narrow context: an interpretation of the Casimir effect).
The existence of singularities are a problem.
The introduction of negative energy in cosmology is not a problem: it is rather the non-observation of theoretically possible negative energy states that is a problem.
Although being theoretically predicted, scientists are satisfied deciding that negative mass does not exist in physics, not only because it is not observed directly, but because of the preposterous Runaway motion paradox arising in general relativity, as described by Hermann Bondi in 1957. It is easier that way, otherwise too much problem.
But the complete Poincaré group describes negative energy and negative mass particles as being real, they are simply the counterpart of all known positive energy particles: electrons, protons, neutrons, photons, neutrinos, etc. but with a negative energy. Discarding this possibility on the altar of Occam's razor is too easy. On the contrary, WIMPs superparticles following from supersymmetry (SuSy) should now be detected already. 40 years AWOL but still considered as "almost around the corner" and "the most plausible explanation for dark matter".
As for the lack of "evidence", your mileage may vary. Any respectable theory has to:
1- be mathematically sound
2- be in agreement with observations
3- make successful predictions
4- be falsifiable with experiments
If a theory agrees with these four points, it should be considered and evaluated accordingly.
My computer is broken so writing from my phone. Limited in what I can do but wanted to throw in some examples of known negative energy in our vacuum. https://en.m.wikipedia.org/wiki/Negative_energy . They go over some phenomena like the negative energy associated with gravity, squeezed light, Hawking radiation, quantum field effects, it's seeming necessity for warp drive, ECT. I wanted to add to it the wierdness in behavior of virtual particles and the time reversal behavior inherent in Feynman diagrams. The nature of time travel inherent in the Lorentz contraction. David's video I posted a bit back where a relativistic solution for a charge shows an exotic (negative) mass associated with either a positive or negative charge where large electric fields can give rise to gravitational fields. A video of an experiment that may be a confirmation of such a field and should be replicatable. This association of negative mass with a charge sounds a lot like polarization of something in the vacuum that has exotic mass. -
#2484 by meberbs on 27 Oct, 2017 03:50
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You are using an equation that both me and Bob012345 explained was wrong from different perspectives (I interpreted your use of variables like dv to be differentials, since that is standard notation. Bob012345 explained it from the perspective that you intended to be writing Δv = change in velocity as you just defined it, which probably was your intention. Note the first post in this thread has a link to help with writing math symbols and Greek letters)I am guessing you haven't studied calculus, that is the incorrect way to take a derivative.
The correct answer is dKe/dV = m*v, which is a function of velocity, not difference in velocity, so by the third or fourth different method, it is still not frame invariant.
Please note, that at this point further "proofs" from you are pointless unless you directly point out something wrong with all of the proofs I have provided. My proofs include directly calculating kinetic energy using the equation for kinetic energy, and I also linked you to a first principles derivation of this equation.
Hi Meberbs,
Change in velocity = final velocity after acceleration - initial velocity before acceleration is frame invarient. Agree?
Therefore the work done to cause the velocity change and associated KE change of the accelerated mass is J = m dV^2 / 2, which is frame invarient.
From either perspective, it appears that you did not read our posts since you are still using the equation that we demonstrated was wrong. -
#2485 by TheTraveller on 27 Oct, 2017 04:53
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You are using an equation that both me and Bob012345 explained was wrong from different perspectives (I interpreted your use of variables like dv to be differentials, since that is standard notation. Bob012345 explained it from the perspective that you intended to be writing Δv = change in velocity as you just defined it, which probably was your intention. Note the first post in this thread has a link to help with writing math symbols and Greek letters)I am guessing you haven't studied calculus, that is the incorrect way to take a derivative.
The correct answer is dKe/dV = m*v, which is a function of velocity, not difference in velocity, so by the third or fourth different method, it is still not frame invariant.
Please note, that at this point further "proofs" from you are pointless unless you directly point out something wrong with all of the proofs I have provided. My proofs include directly calculating kinetic energy using the equation for kinetic energy, and I also linked you to a first principles derivation of this equation.
Hi Meberbs,
Change in velocity = final velocity after acceleration - initial velocity before acceleration is frame invarient. Agree?
Therefore the work done to cause the velocity change and associated KE change of the accelerated mass is J = m dV^2 / 2, which is frame invarient.
From either perspective, it appears that you did not read our posts since you are still using the equation that we demonstrated was wrong.
Hi Meberbs,
The calculation of the work needed to be done on the mass to achieve the dV change is correct.
It is also frame invarient and does not need to calc fuel potential energy, fuel mass exhausted nor the fuel mass exhaust velocity.
For a P-P drive, the equations and method works fine.
So far I know of 4 P-P drive types
1) Shawyer EmDrive
2) Fetta drive
3) White QV drive
4) Woodward MEGA drive
All feature the same effect. Propulsion without needing to exhaust mass. if you still desire to believe none of the 4 work, maybe tell Dr. Rodal the MEGA drive doesn't work.
As I see it, there are 2 ways to calc the work done by P-P drives when they accelerate mass:
1) Work = (N^2 t^2) / 2 m.
2) Work = change in KE via change in velocity.
I prefer the 1st equation as it doesn't need to know velocity. -
#2486 by WarpTech on 27 Oct, 2017 05:05
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I am guessing you haven't studied calculus, that is the incorrect way to take a derivative.Kinetic energy is not frame invariant, it is a function of velocity which is obviously not frame invariant. It is also not a linear function of velocity, so differences in kinetic energy also cannot be frame invariant.
The change in KE and work done can be frame invarient as follows.
Acceleration causes a change in velocity, which is frame invarient. All frames observe the same change in velocity, the same dV.
Using the dV, the change in KE can be calculated as dKE = m dV^2 / 2. Work done is then equal to dKE.
The correct answer is dKe/dV = m*v, which is a function of velocity, not difference in velocity, so by the third or fourth different method, it is still not frame invariant.
Please note, that at this point further "proofs" from you are pointless unless you directly point out something wrong with all of the proofs I have provided. My proofs include directly calculating kinetic energy using the equation for kinetic energy, and I also linked you to a first principles derivation of this equation.
Hi Meberbs,
Change in velocity = final velocity after acceleration - initial velocity before acceleration is frame invarient. Agree?
Therefore the work done to cause the velocity change and associated KE change of the accelerated mass is J = m dV^2 / 2, which is frame invarient.
Do you mean;
d(V2) or (dV)2 ?
The way you write it is not conventional, and it is not at all obvious to be one or the other. Parenthesis do amazing things!
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#2487 by WarpTech on 27 Oct, 2017 05:26
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All types of energy gravitate (electromagnetic energy gravitates: energy density, Maxwell stress tensor and Poynting vector are all in the stress-energy tensor and hence they count as E/c^2 , as pressure also does). The only energy not included is the gravitational potential energy.
Yes, given what is known about Quantum Mechanics a unified theory with GR is necessary to understand the Big Bang, what is inside Black Holes, probably to understand Dark Energy and many other things
"The only energy not included is the gravitational potential energy." (emphasis mine)
Now I get it! These are vacuum solutions because they do not require any source, no particles, no field, nothing at all. Schwarzschild excludes the mass or singularity and gravitational waves are waves in "empty" space. For some insane reason, someone had this notion that nothingness can have a shape and somehow matter will "know" what that shape is and follow it.
In my QG model, Flat space-time is equilibrium between; matter, the ZPF and the URRF (Universal Radiation Reaction Field). A gradient in this equilibrium "IS" a gravitational field. Therefore, in the model, the ONLY energy in the model "IS" the gravitational potential energy. That is what I'm describing.
So it is exactly that which is excluded in GR. Where, space-time curvature is interpreted as "causative" rather than "descriptive". Is precisely where my model describes the QM of what is happening.
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#2488 by wicoe on 27 Oct, 2017 05:37
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The calculation of the work needed to be done on the mass to achieve the dV change is correct.
Regardless of how many times you repeat the same thing, it does not become true. Your calculation is NOT correct, as has been shown many times. The work needed to be done to accelerate a mass by dv equals the change in kinetic energy, which is "KE after" minus "KE before", i.e. m*(v0+dv)^2/2 - m*v0^2/2. This cannot be approximated by m*(dv)^2/2 if v0 is non-zero. -
#2489 by TheTraveller on 27 Oct, 2017 05:44
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Do you mean;
d(V2) or (dV)2 ?
The way you write it is not conventional, and it is not at all obvious to be one or the other. Parenthesis do amazing things!
Hi WT,
Joules of work done by a P-P drive to alter mass velocity = mass in kgs TIMES (change in velocity (m/sec) squared) DVIDED by 2
Here is an example:
Take the MEGA interstellar ship, mass = 35t. It does a 1km/sec velocity change to match velocity to some object in space. How much work was needed to be done on the ship's mass to achieve the velocity change?
35,000 x (1,000^2) / 2 = 17.5 x10^9 Joules of work was done by the P-P MEGA drive on the ship's mass to achieve the 1km/sec velocity change. -
#2490 by TheTraveller on 27 Oct, 2017 05:53
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The calculation of the work needed to be done on the mass to achieve the dV change is correct.
Regardless of how many times you repeat the same thing, it does not become true. Your calculation is NOT correct, as has been shown many times. The work needed to be done to accelerate a mass by dv equals the change in kinetic energy, which is "KE after" minus "KE before", i.e. m*(v0+dv)^2/2 - m*v0^2/2. This cannot be approximated by m*(dv)^2/2 if v0 is non-zero.
Hi Wicoe,
Please refer to my example to WT and calc the work needed to be done by a P-P MEGA drive on the 35t ship's mass to achieve a 1km/sec velocity change, so as to match velocity with some object in space.
Using an initial velocity of another rest frame, will generate a different KE change and work done in every rest frame. As there is no fuel mass and no potential energy change of the fuel mass, nor exhaust mass nor mass exhaust velocity to adjust the KE change, how to make each frame see the same change in KE? -
#2491 by Eusa on 27 Oct, 2017 06:40
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The last gravitational and luminal observations of merging neutron stars falsified bigravity (https://arxiv.org/abs/1710.06394 & https://arxiv.org/abs/1703.07785). Instead of dipole membranes there can be "bigravitational" emergent mechanisms in the Einsteinian monogravity: the info signals of gravitational changes can occur as bias of spherical symmetry in parts of sum curvature. Info signals carries energy and can affect extra or lack of gravitational hyper liquid current in vacuum implicating dark mass or dark energy phenomena.
In the regularly changing galaxial systems info signals form loop structure (spiral galaxies, galaxy clusters, bullet cluster) consisting energy i.e. mass. Between galaxial systems there can be lack of loop structures in respect of vacuum average. Modified gravity without differing gravity scalar-tensor function or acceleration function but with genuine mass, not particle-based but big-loop-based... -
#2492 by meberbs on 27 Oct, 2017 07:12
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The calculation of the work needed to be done on the mass to achieve the dV change is correct.
It seems by "the calculation" you are referring to your calculation and you are still ignoring everything that everyone else has said.
I would greatly appreciate it if you could write a post that actually responds to things that you have been told, rather than repeating things repeatedly demonstrated to be wrong.So far I know of 4 P-P drive types
There are precisely 0 drives demonstrated with propellantless propulsion that have been conclusively demonstrated. I am also fairly certain that Rodal has never claimed that the MEGA drive works via true propellantless propulsion.
...
All feature the same effect. Propulsion without needing to exhaust mass. if you still desire to believe none of the 4 work, maybe tell Dr. Rodal the MEGA drive doesn't work.As I see it, there are 2 ways to calc the work done by P-P drives when they accelerate mass:
The first equation only works in the initial rest frame of the object. I have already demonstrated that fact.
1) Work = (N^2 t^2) / 2 m.
2) Work = change in KE via change in velocity.
I prefer the 1st equation as it doesn't need to know velocity.
The second is simply not an equation. If by change in velocity, you mean an equation that involves (v2-v1)^2 you are simply wrong. If the equation involves (v2^2) - (v1^2) then it is correct.
Either way, kinetic energy cannot be calculated in a special way for a propellantless drive. Objects do not carry around a flag saying what method was used to accelerate them, so kinetic energy is calculated them same way for all of them, 0.5*m*v^2, and your methods are simply incompatible with this fundamental equation.35,000 x (1,000^2) / 2 = 17.5 x10^9 Joules of work was done by the P-P MEGA drive on the ship's mass to achieve the 1km/sec velocity change.
This is only true if the ship starts at rest in the relevant frame.Using an initial velocity of another rest frame, will generate a different KE change and work done in every rest frame. As there is no fuel mass and no potential energy change of the fuel mass, nor exhaust mass nor mass exhaust velocity to adjust the KE change, how to make each frame see the same change in KE?
You are finally starting to see the problem. There is no way to make a true propellantless propulsion obey conservation of energy, since the same work will generate a different kinetic energy in every frame, and there is no propellant to balance this. Your repeated attempts to do so simply result in you using equations that simply give wrong and inconsistent answers. -
#2493 by flux_capacitor on 27 Oct, 2017 12:51
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The last gravitational and luminal observations of merging neutron stars falsified bigravity (https://arxiv.org/abs/1710.06394 & https://arxiv.org/abs/1703.07785).
Let's make it clear that there are two kinds of bimetric gravity theories. "Bigravity" in these papers is about massive gravitons; whereas the "negative mass bigravity" I talked previously is about two coupled metrics with conjugate geometries in a single Riemannian manifold. -
#2494 by Rodal on 27 Oct, 2017 12:58
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Regarding Phil (TheTraveller)'s discussion bringing up the MEGA drive into the fore, the official explanation for the energy generation in the MEGA drive is contained here:
http://ssi.org/wp-content/uploads/2017/09/SSI_NIAC2017_QandA.pdfQuoteQ5. Why doesn’t the MEGA drive result in free energy, and therefore used for energy
generation?
The MEGA drive does not violate energy conservation. The kinetic energy comes from the
gravitational field, not from the electrical power applied to the device. There is a large
gravitational potential in the universe we are tapping into to gain kinetic energy of the
device. If we take a small amount of energy, practically no loss will be noticed by the
whole universe. There are far more efficient ways of extracting energy, for example, from
nuclear or solar power. Trying to extract energy from gravitation via the Mach effect is very
inefficient.
The benefit of Mach effect propulsion is to avoid carrying propellant for long space
missions, particularly for interstellar missions.
For emphasis: << The kinetic energy [of the center of mass of the spaceship] comes from the gravitational field, not from the electrical power applied to the device.>>
This is completely opposed to Roger Shawyer's explanation for the EM Drive, for which Shawyer claims that 100% of the kinetic energy of the [center of mass of a spaceship driven by the] EM Drive comes from electric power supplied to the EM Drive.
Thus it is up to Shawyer to explain (and TT if he wishes) how can the EM Drive result in propellantless propulsion kinetic energy that eventually (after a certain time) must exceed the input electric power, and to address the frame-dependence problem. This cannot be done on the basis of a completely different model that argues that none of the kinetic energy [of the center of mass of the spaceship] comes for the electrical power applied to the device.
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#2495 by OnlyMe on 27 Oct, 2017 17:04
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The whole issue reminds me of a quote from, “Thinking fast and slow“, by Daniel Kahneman
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When you say with certainty that, no acceleration can occur without interacting with something outside the frustum, you are saying you know everything there is to know. If your argument had been phrased as, this is what I believe, rather than as a certainty that implies we already know all there is to know, it would have been better, the way I read your comments.
Daniel Kanehman has a Nobel Memorial Prize in Economics, "the dismal science" so called for many reasons (including the fact that one cannot have well-controlled experiments in Economics), including that this prize has the dubious distinction that it has been conferred on the same year to people having diametrically different economic opinions.
What I am saying is not (like you incorrectly claim) that I know everything (I never said that), but that I am confident enough to place a financial bet with you that it will turn out as I wrote concerning conservation of momentum, internal and external fields. Unfortunately there is no option market to place such a bet at the moment, as I think that it would be a good financially rewarding bet to place (of course it would be a matter of what would be the odds in such a market...)
....
Dr. Rodal,
I think I must apologize. After your post above I had to go back and re-read the post string leading up to this point. When I used the words, “... you are saying you know everything there is to know.“ I had not intended it as a personal comment. Both in that post and my earlier post where I said, “... This last sentence is once again an arrogant statement...”, I had intended to be referring to the general “voice” I read in the comments I was responding to. I was attempting to point out a difference between statements of certainty, as opposed to generally accepted or as you phrased it above when you said, “... I am confident enough...”.
These are largely theoretical discussions often spanning boundaries between more than one theoretical model. Discussions about the details of interactions which would be taking place under conditions we have not yet experimentally observed in sufficient detail, to know with certainty just what we can know with certainty....
To your offer of a bet, first I am not sure I was challenging CoM, as much as suggesting that we may not know enough to say we know all there is to know about how CoM and CoE fit into the larger context, of some aspects of the heavily theoretical discussions within this thread. Still, I have already placed a significant bet in support of DIY EmDrive experiments, not because I know or even believe there is any useable thrust, but because I saw enough reason to believe there was and remains merit in finding out... one way or the other.
Daniel Kanehman has a PhD in Psychology, not economics where he received a Nobel prize. And his book, “Thinking fast and slow” is about the psychology of critical thinking and decision making. I include again the following quote from his book, "... Which describes a puzzling limitation of our mind: our excessive confidence in what we believe we know, and our apparent inability to acknowledge the full extent of our ignorance and the uncertainty of the world we live in.", because I thought it captured a bit of the point I was attempting to make. An importance in understanding the difference between what we know as a matter of certainty (past experience and observation) and what we believe or think we know, as we project conclusions based on past experience to situations and conditions beyond our experience. Until we power up a functional EmDrive and send it off on a long deep space journey, we cannot know with any certainty, the answer to many of the issues being debated. And even then finding answers will depend on whether whatever we send off into the void is equipped to attempt to answer those questions.
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#2496 by Bob012345 on 27 Oct, 2017 19:02
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There are precisely 0 drives demonstrated with propellantless propulsion that have been conclusively demonstrated. I am also fairly certain that Rodal has never claimed that the MEGA drive works via true propellantless propulsion.
I'd say some have been shown fairly convincingly if not yet conclusively. But what exactly constitutes a 'true' PP drive? Are you basically saying a 'true' PP drive violates physics or that if it can be explained by an interaction with the universe or some such thing, it's not really a PP drive. Is that part of your basic operating definition? What would you call a working EMdrive, a pseudo, a virtual or an effective PP?Using an initial velocity of another rest frame, will generate a different KE change and work done in every rest frame. As there is no fuel mass and no potential energy change of the fuel mass, nor exhaust mass nor mass exhaust velocity to adjust the KE change, how to make each frame see the same change in KE?
You are finally starting to see the problem. There is no way to make a true propellantless propulsion obey conservation of energy, since the same work will generate a different kinetic energy in every frame, and there is no propellant to balance this. Your repeated attempts to do so simply result in you using equations that simply give wrong and inconsistent answers.
In answer to both, there is another way. The total change in KE if you include the 'exhaust', however that is interpreted, is invariant but the change in ship KE depends on observer if you include both parts I showed. The 'exhaust' comes from realizing that any force truly operating from within a reference frame is acting like that reference frame has infinite inertia. You can model the situation by assuming the EMDrive conserves momentum with a really really big mass, the reference frame it's in, and let that mass go to infinity in the limit which balances everything out for all observers. -
#2497 by Rodal on 27 Oct, 2017 19:39
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The bigravity theory made a prediction (now apparently falsified, see EUSA's post: https://forum.nasaspaceflight.com/index.php?topic=42978.msg1742543#msg1742543 ) regarding gravitational waves.The last gravitational and luminal observations of merging neutron stars falsified bigravity (https://arxiv.org/abs/1710.06394 & https://arxiv.org/abs/1703.07785).
Let's make it clear that there are two kinds of bimetric gravity theories. "Bigravity" in these papers is about massive gravitons; whereas the "negative mass bigravity" I talked previously is about two coupled metrics with conjugate geometries in a single Riemannian manifold.
For a fair comparison, one needs detailed time-dependent predictions regarding gravitational waves from the bimetric gravitational theory using the Janus cosmology model. It is very unclear to me (at least) what are the detailed features of the gravitational waves predicted by this theory. For another comparison, scalar-tensor gravitational theories have also made (falsifiable) predictions about gravitational waves. -
#2498 by meberbs on 27 Oct, 2017 19:47
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Propellantless propulsion by definition is something accelerating without pushing on anything else. This by definition violates Newton's third law and conservation of momentum, and it is simple to go from there and show it also violates conservation of energy.There are precisely 0 drives demonstrated with propellantless propulsion that have been conclusively demonstrated. I am also fairly certain that Rodal has never claimed that the MEGA drive works via true propellantless propulsion.
I'd say some have been shown fairly convincingly if not yet conclusively. But what exactly constitutes a 'true' PP drive? Are you basically saying a 'true' PP drive violates physics or that if it can be explained by an interaction with the universe or some such thing, it's not really a PP drive. Is that part of your basic operating definition? What would you call a working EMdrive, a pseudo, a virtual or an effective PP?
I can't answer your question of what to call a working emDrive without knowing how it works. It is much more likely that a working emDrive pushes on something unknown than violates conservation of momentum. It is much more likely than either of those that there is no such thing as a working emDrive, and it is just an experimental artifact.
I am not sure what you are trying to say here. Specifically, I can't parse the phrase "any force truly operating from within a reference frame " in any meaningful way.Using an initial velocity of another rest frame, will generate a different KE change and work done in every rest frame. As there is no fuel mass and no potential energy change of the fuel mass, nor exhaust mass nor mass exhaust velocity to adjust the KE change, how to make each frame see the same change in KE?
You are finally starting to see the problem. There is no way to make a true propellantless propulsion obey conservation of energy, since the same work will generate a different kinetic energy in every frame, and there is no propellant to balance this. Your repeated attempts to do so simply result in you using equations that simply give wrong and inconsistent answers.
In answer to both, there is another way. The total change in KE if you include the 'exhaust', however that is interpreted, is invariant but the change in ship KE depends on observer if you include both parts I showed. The 'exhaust' comes from realizing that any force truly operating from within a reference frame is acting like that reference frame has infinite inertia. You can model the situation by assuming the EMDrive conserves momentum with a really really big mass, the reference frame it's in, and let that mass go to infinity in the limit which balances everything out for all observers.
Your description of the emDrive at the endbasically is saying that there is something the emDrive is pushing against to balance out energy and momentum. You are referring to what it is pushing against as a "reference frame" but this doesn't make sense because a reference frame is a mathematical construct, not a physical object. -
#2499 by flux_capacitor on 27 Oct, 2017 19:58
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Propellantless propulsion by definition is something accelerating without pushing on anything else. This by definition violates Newton's third law and conservation of momentum, and it is simple to go from there and show it also violates conservation of energy.
I can't answer your question of what to call a working emDrive without knowing how it works. It is much more likely that a working emDrive pushes on something unknown than violates conservation of momentum. It is much more likely than either of those that there is no such thing as a working emDrive, and it is just an experimental artifact.
This is why Rodal explained many times in these threads the difference between a closed system i.e. a true reactionless drive (which could not exist without violating laws of conservation of momentum) VS an open system as represented by a propellantless drive (in the sense the drive would not carry any propellant, i.e. nothing would be thrown off the back of the spacecraft from something stored in a tank aboard; but still this drive would exchange momentum with external mass-energy through a field). That kind of propellantless drive, which would not be reactionless, representing an open system, used to be referred to as field propulsion.
