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#1260 by Bob012345 on 01 Aug, 2019 20:16
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Energy and momentum conservation both have to happen. You can't just freely convert between forms of energy. When you do have a mechanism that converts say electrical energy into kinetic energy, physics states that the mechanism will also conserve momentum. If the kinetic energy goes into one object to give it momentum in one direction, the mechanism will need to provide equal and opposite force to something else, and make that something else move in the opposite direction. Kinetic energy will not necessarily be distributed equally for equal momentum distribution if the objects have different masses. (And photons are a valid thing that could be either of the things that end up with momentum)CofM is obeyed.
For the countless time:
If a system starts at rest, ends up moving, and you can't point to anything else moving in the opposite direction, that is the literal definition of breaking conservation of momentum. You clearly have issues with your understanding of photon momentum, but those don't matter for seeing that you are breaking conservation of momentum, since you just turn the drive off, let the photons all get absorbed by the cavity walls, and see that if the device works as you claim, conservation of momentum is broken.
Serious question (not trying to be a troll). If the system has movement imparted to it through energy (or mass that was converted to energy), then you wouldn't see anything else moving in the opposite direction, right? Even if you can measure the input energy that was used to impart the movement?Please clarify a couple of points. It seems the general thinking on the EmDrive is that what happens in the cavity stays in the cavity, except thermal photons. Correct me if I'm wrong, but it seems all those bouncing microwaves inside would induce currents in the EmDrive surface which themselves would produce fields and photons outside which thus can shed momentum. And even just considering thermal photons, couldn't the truncated cone shape preferentially radiate power in one direction? Thanks.
RF should not be able to significantly escape from a well designed cavity due to RF skin depth in metal, etc. Radiation from surface currents would all be inside the cavity, and is tied in with the process of reflection of the internal waves. Even if it did escape, all you are getting is a photon rocket with the escaped power at best, and there are more direct and efficient ways to make a photon rocket. In this regime, electrodynamics is well tested and understood, so it is unlikely that there is any unknown coupling. Assuming that the emDrive does work by some mechanism, then there would have to be something else carrying away the momentum for momentum conservation to hold. The problem with statements like those from TT and Shawyer are that they claim there is no new physics, and point to no balancing thing carrying away the opposite momentum, yet they still claim momentum conservation.
Thanks. That makes sense about radiation staying internal, except heat unless the cavity was very thin, within skin depth but then it probably wouldn't be able to keep its shape under intense radiation pressure.
Speaking of cavities and radiation pressure, this is probably old news and maybe unless but I'll reference it in case it's not.
https://www.researchgate.net/profile/Jacob_Pate3/publication/329230432_Electrostatic_tuning_of_mechanical_and_microwave_resonances_in_3D_superconducting_radio_frequency_cavities/links/5c12b301299bf139c756be10/Electrostatic-tuning-of-mechanical-and-microwave-resonances-in-3D-superconducting-radio-frequency-cavities.pdf -
#1261 by meberbs on 01 Aug, 2019 20:59
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Oh yeah, I have suggestions on where the answer lies. In fact most all papers I've read are all saying about the same thing in different terms. Mass generates momentum we call gravity...massless objects generate what science fiction calls antigravity. But these are just words...no one should think any more about it.
If you have seen papers, you should link to them so others can judge what they say.
Besides that, the actual reason no one should think in depth about what you said is that we experimentally know that your statement about massless particles and anti-gravity is false. We know this because of measurements of the gravitational bending of light and gravitational redshift, both of which effectively amount to a description of gravitational "force" acting on light in the typical way. (Note, this is not a technically correct explanation, since gravity in GR is a bending of space-time rather than a force, but either way claiming that massless particles are somehow anti-gravity is simply not consistent with reality.) -
#1262 by Bob Woods on 01 Aug, 2019 22:51
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Nice to see you back, Dave.
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#1263 by TheTraveller on 01 Aug, 2019 23:06
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Oh yeah, I have suggestions on where the answer lies. In fact most all papers I've read are all saying about the same thing in different terms. Mass generates momentum we call gravity...massless objects generate what science fiction calls antigravity. But these are just words...no one should think any more about it.
Hi RfMwGuy/Dave,
Mate good to see you back.
What the intended result are 2 sets of high quality data.
1) Very clear thrust at the +20mN level or greater from 100Wrf.
2) Very clear data that during acceleration, trapped photon wavelength increases, due to lost photon momentum transferred to gained accelerated mass momentum. Plus data to show there are no increased photon wavelengths when acceleration does not occur, ie no mass momentum gain.
I have posted here several times & advised various DIY EmDrive test stand builders that the goal to measure uN level thrust, requiring elimination of vibration, may cause the elimination of thrust as reported by Roger many years ago.QuoteA number of methods have been used in the UK, the US and China to measure the
forces produced by an EmDrive thruster. In each successful case, the EmDrive force
data has been superimposed on an increasing or decreasing background force,
generated by the test equipment itself.
Indeed, in the UK when the background force changes were eliminated, in an effort
to improve force measurement resolution, no EmDrive force was measured.
http://www.emdrive.com/EmDriveForceMeasurement.pdf
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#1264 by meberbs on 01 Aug, 2019 23:48
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One should not ask for suggestions simply to attack it with other's theories. Since thise theories are not of your own construct, I consider your posts of little value. By the way, who are you really? Or have you chosen to remain anonymous?
I would appreciate it if you did not blatantly misrepresent my post like that. I pointed to well known experiments that contradicted your description. This does not involve "other people's theories." It is also completely inappropriate to call something an attack, just for pointing out evidence that contrary to your statements. If you don't want any critiques of your ideas you are free to not share them, but that of course also means you lose the opportunity to learn whether your ideas actually hold water. On the other hand you are basing what you are saying on other people's theories and have not shared enough information to find any details on said theories.
As to who I am, I choose not to share that with the entire internet, but there are people on this site who I have shared relevant information with, people who know me in real life would have no trouble identifying me based on forum name, and you formerly were a mod on this site and therefore presumably would have had access to a post where I shared my background and name, besides having access to my e-mail address which can easily be used to track down much of the same information. -
#1265 by D_Dom on 02 Aug, 2019 00:42
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Guys, lets go easy . If you can't be excellent to each other, maybe this is not the site for you. This is not directed at any individual, please keep a focus on scientific method and avoid personal attacks.
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#1266 by rfmwguy on 02 Aug, 2019 02:13
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Hello Bob and Phil...I rarely have time to follow things too closely. The 20 mN per 100W is quite a goal...a 10x improvement on my humble project back in 2015. Still wondering why tajmar uses low Q design after all these years.
Oh, there is a solid attempt to lure me out of retirement.
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#1267 by dustinthewind on 02 Aug, 2019 03:28
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New article by Tajmar on tests on the Emdrive and on Woodward device:
https://www.sciencedirect.com/science/article/pii/S009457651832071X
"Results of the tests performed between August and September 2018 are presented, but no final conclusions can be drawn."
We already had this round of testing results though, didn't we?CofM is obeyed.
For the countless time:
If a system starts at rest, ends up moving, and you can't point to anything else moving in the opposite direction, that is the literal definition of breaking conservation of momentum. You clearly have issues with your understanding of photon momentum, but those don't matter for seeing that you are breaking conservation of momentum, since you just turn the drive off, let the photons all get absorbed by the cavity walls, and see that if the device works as you claim, conservation of momentum is broken.
Serious question (not trying to be a troll). If the system has movement imparted to it through energy (or mass that was converted to energy), then you wouldn't see anything else moving in the opposite direction, right? Even if you can measure the input energy that was used to impart the movement?
The photons in the cavity have zero net momentum even if they lose energy. For the cavity to accelerate and remain in motion would mean something escaped the cavity. This would mean the photons imparted energy into something that escaped the cavity. This interaction I suspect would also give the effect where the photons are heavy and then light. The photons are a directed result of the electric field of the electrons so it may be the electrons that are becoming heavy then light. (sort of like mach effect or maybe like orbiting black holes that throw energy into space time waves. ) (black holes seperated have stored potential energy that has effective mass in space time. As the black holes spin down the black holes speed up converting that stored potential energy with effective mass to their Lorentz contraction and Relativistic Mass
http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/tdil.html
However this effective mass is thrown off as space times waves and as a result the black holes slow down losing this effective mass such that real effective mass is thrown off into space time (think of the wave as repulsive or attractive which slows the black hole as its thrown off). I think this is the effective mass that could escape the cavity and be used as the impulse engine.
I was speculating a transverse magnetic mode in the cavity where electrons in the cavity are accelerated up and down but in a way you change their acceleration in one direction as opposed to the other direction. Problem is electron velocity may need to be ramped up to near light speed and very large accelerations. The way to accomplish this is low electron density which maximizes velocity and acceleration. Electron density in copper is too dense and they are slow. Superconductors provide low density for electron pairs but are hard to keep cool. My idea was to introduce an electron ring inside the cavity with Helmholtz coils and accelerate that electron ring with the transverse magnetic mode. (beware large accelerations on electrons could induce gamma radiation penetrating cavities. Experimenters beware.)
The trick then is to make the electrons follow a path which maximizes their asymmetry in acceleration.
Stored energy in cavities are great way to enhance energy stored in the electrons and may enhance the energy conversion process. Its sort of related to cavities we use on earth. Combustion engines are cavities and the higher the pressure and longer the stroke length the more energy can be converted from thermal energy to motion of a car - leaving the gas that escapes cooler. (by the way automatic transmissions are less efficient because they allow larger rpm's - need large torque and low rpm's) The photon rockets also use large quality to enhance energy conversion of photon frequency to mirror acceleration. Normally thrust from photons are dismal but not with a photon rocket.
If electrons can be made to intact with space time the efficiency of converting the photon frequency to space time thrust may not be dismal. I am also not convinced that warping of space time as propulsion is a dismal form of propulsion. In fact it is suspected asymmetrically orbiting black holes may effectively propel themselves out of their own host galaxy by asymmetrically emitted gravity waves and I was reading relativistic objects could absorb as much as 10% of the energy of a space time wave passing by, which is much greater than the % of energy absorbed from a photon impact at normal velocities. I think the trick is to use the stored potential photon energy to be converted to electron relativistic mass. This relativistic coupling I think would enhance the asymmetric coupling to space time and I think it would be similar to scooting ones butt across the carpet so to speak. Pick Butt up, it becomes light or low friction. Push Butt down to enhance friction, but for relativistic mass it's large velocity, now accelerate hard.
Photo attached of a supposed path for the electrons to follow which would induce asymmetry in acceleration. Y = displacement, X = time or w*t. This one probably has too many frequencies involved but it illustrates better the asymmetry. I think you put this into an equation for the electrons as harmonic oscillators that leaves the EM field as an unknown. The known is the path of the electron ring as the oscillators. You then solve for the EM field that needs to be put in to get the desired behavior of the electron ring to traverse the cavity.
https://wiki.jlab.org/ciswiki/images/e/ee/PhysRevAccelBeams.19.122001.pdf
Multiple harmonic frequencies resonant cavity design
and half-scale prototype measurements for a fast kicker
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#1268 by meberbs on 02 Aug, 2019 06:02
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(by the way automatic transmissions are less efficient because they allow larger rpm's - need large torque and low rpm's)
Off topic, but see here for an explanation of why you are not correct. The issue with automatic transmissions used to be the lack of direct mechanical coupling, causing a loss in power. Nowadays automatic transmissions are the more efficient ones, in part because they can use mechanical coupling when cruising, and also because they now have more gears and allow staying in the optimal RPM range for a wider range of speeds.The photon rockets also use large quality to enhance energy conversion of photon frequency to mirror acceleration. Normally thrust from photons are dismal but not with a photon rocket.
Typically the term "photon rocket" refers to the non-recycling version. For a recycling one like in the video you shared, it basically is a way of indirectly pushing against whatever the mirror on the other end is attached to, and the efficiency depends on the relative mass of the other mirror.If electrons can be made to intact with space time the efficiency of converting the photon frequency to space time thrust may not be dismal.
This is another one of those ideas that immediately brings up the question of how exactly you propose to do this, and why you think this could produce useful thrust.I am also not convinced that warping of space time as propulsion is a dismal form of propulsion. In fact it is suspected asymmetrically orbiting black holes may effectively propel themselves out of their own host galaxy by asymmetrically emitted gravity waves and I was reading relativistic objects could absorb as much as 10% of the energy of a space time wave passing by, which is much greater than the % of energy absorbed from a photon impact at normal velocities.
I have explained this to you repeatedly: If you look at a photon reflecting off of a mirror from a variety of reference frames, you will see different results for the energy transfer and can find any answer you want from near 100% transfer of energy from the photon to the mirror, to frames where the mirror has high velocity towards the direction the photon is coming from, and the mirror transfers energy to the photon. All of these accurately describe the same event, and none of it is any different than photon rocket propulsion. (The basic kind without recycling, just a factor of 2 since it is an externally provided photon being reflected.) This is dictated by the principle of relativity, that the laws of physics do not depend on choice of inertial reference frame. The example with back holes only indicates the extreme amount of energy that is released in order to provide the high acceleration.
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#1269 by rfmwguy on 02 Aug, 2019 11:06
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Fellas, we are still stuck at assuming mass exchange is the key and there is balance within a frustum. The arguments of mass action and reaction must be set aside for this to come to a resolution. Imho, an asymmetrical condition occurs within the frustum generated by massless forces of photonic energy...what that is...we should continue to explore. Firmly convinced it's the answer. I'm back to the shadows again.
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#1270 by dustinthewind on 02 Aug, 2019 13:54
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Fellas, we are still stuck at assuming mass exchange is the key and there is balance within a frustum. The arguments of mass action and reaction must be set aside for this to come to a resolution. Imho, an asymmetrical condition occurs within the frustum generated by massless forces of photonic energy...what that is...we should continue to explore. Firmly convinced it's the answer. I'm back to the shadows again.
The main point I made above for you is that the light in the cavity has no net momentum so if the cavity accelerates the light in the cavity can't account for the equal and opposite momentum. If we still believe in momentum conservation in the universe then we need this. It has to be something that escaped the cavity for momentum to be conserved, else the cavity will quickly come to a stop. I gave what I think gives that effective escaping mass is to carry away equal and opposite momentum.
Imagine pulling on an electron when its about twice as heavy via its relativistic effective mass via its velocity, barely giving it time to change its effective mass via the still present space time deformation. I.e. space time doesn't have the time to react to change its effective mass quickly enough.
The gradual deceleration of the electron allows its effective mass to gradually change during the deceleration.
So pulling 10E9 times per second on 10E9 electrons that are twice as heavy, and pushing when they are only 1.5 times as heavy gives the effect of 5E9 electrons slamming into one wall 10E9 times. But what changes their effective mass? Why not relativistic effective mass? How do black holes and neutron stars do it?
I think its possible that energetically inflated space might be gravitationally repulsive and accounts for dark energy that is pushing the universe apart and that it migrates to the great voids. Like hot air that floats away from gravity. Thermally inflated space speeds up time causing the galaxies to appear to rotate faster and seeming enhance the gravitational well in which they exist. So imagine the plank length being inflated and the thermally excited space ticking faster via its thermal excitation. So in a sense I think it may appear as negative energy. In a sense all that lost energy by the black holes, or electrons in stars, being trapped in the voids pushing our universe apart.
great inflation of the universe being related. -
#1271 by dustinthewind on 02 Aug, 2019 15:53
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What matters is he is keeping the RPMs down. This allows more atomic reflections off of a receding cylinder wall transferring more thermal energy into the energy of the vehicle. you can put more gears on a manual transmission as well. You also have a clutch for coasting. a lot of those automatic transmission will downshift increasing RPMs and decreasing efficiency. It is related because we're talking about the efficiency of converting photon energy in the cavity to propellantless propulsion via increasing or quality of the cavity. Lowering the RPMs increases quality. in our case increasing the number of times the photons accelerate the electrons back and forth increases the quality.(by the way automatic transmissions are less efficient because they allow larger rpm's - need large torque and low rpm's)
Off topic, but see here for an explanation of why you are not correct. The issue with automatic transmissions used to be the lack of direct mechanical coupling, causing a loss in power. Nowadays automatic transmissions are the more efficient ones, in part because they can use mechanical coupling when cruising, and also because they now have more gears and allow staying in the optimal RPM range for a wider range of speeds.Quote
Exactly. The efficiency of energy transfer is governed by the relative mass of the particle collision with the relative effective mass of the vehicle and the number of times it's allowed to collide and transfer energy. Heavier vehicles are less fuel-efficientThe photon rockets also use large quality to enhance energy conversion of photon frequency to mirror acceleration. Normally thrust from photons are dismal but not with a photon rocket.
Typically the term "photon rocket" refers to the non-recycling version. For a recycling one like in the video you shared, it basically is a way of indirectly pushing against whatever the mirror on the other end is attached to, and the efficiency depends on the relative mass of the other mirror.Quote
I already stated, by changing the effective mass of the electrons involved.If electrons can be made to intact with space time the efficiency of converting the photon frequency to space time thrust may not be dismal.
This is another one of those ideas that immediately brings up the question of how exactly you propose to do this, and why you think this could produce useful thrust.QuoteI am also not convinced that warping of space time as propulsion is a dismal form of propulsion. In fact it is suspected asymmetrically orbiting black holes may effectively propel themselves out of their own host galaxy by asymmetrically emitted gravity waves and I was reading relativistic objects could absorb as much as 10% of the energy of a space time wave passing by, which is much greater than the % of energy absorbed from a photon impact at normal velocities.
I have explained this to you repeatedly: If you look at a photon reflecting off of a mirror from a variety of reference frames, you will see different results for the energy transfer and can find any answer you want from near 100% transfer of energy from the photon to the mirror, to frames where the mirror has high velocity towards the direction the photon is coming from, and the mirror transfers energy to the photon. All of these accurately describe the same event, and none of it is any different than photon rocket propulsion. (The basic kind without recycling, just a factor of 2 since it is an externally provided photon being reflected.) This is dictated by the principle of relativity, that the laws of physics do not depend on choice of inertial reference frame. The example with back holes only indicates the extreme amount of energy that is released in order to provide the high acceleration.
The reason photon propulsion is ineffective is because of the low percentage of energy transfer between the photon and the object it collides with. Very small change in frequency. -
#1272 by meberbs on 02 Aug, 2019 16:41
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Please read the link I previously provided, you apparently don't get the fact that modern automatic transmissions beat manual on efficiency. Your explanation of why you usually want to keep RPMs down is also wrong see here. There are multiple factors that go into it which is why you need an optimal range, and why you don't just always drive in high gear.
What matters is he is keeping the RPMs down. This allows more atomic reflections off of a receding cylinder wall transferring more thermal energy into the energy of the vehicle. you can put more gears on a manual transmission as well. You also have a clutch for coasting. a lot of those automatic transmission will downshift increasing RPMs and decreasing efficiency.(by the way automatic transmissions are less efficient because they allow larger rpm's - need large torque and low rpm's)
Off topic, but see here for an explanation of why you are not correct. The issue with automatic transmissions used to be the lack of direct mechanical coupling, causing a loss in power. Nowadays automatic transmissions are the more efficient ones, in part because they can use mechanical coupling when cruising, and also because they now have more gears and allow staying in the optimal RPM range for a wider range of speeds.It is related because we're talking about the efficiency of converting photon energy in the cavity to propellantless propulsion via increasing or quality of the cavity. Lowering the RPMs increases quality. in our case increasing the number of times the photons accelerate the electrons back and forth increases the quality.
Even if you were getting your facts straight on this, it would still not be a meaningful analogy. A high number of reflections increases the total energy stored in the cavity, but the electrons are oscillating at the injected frequency no matter what, just more of them are moving with higher fields. But since this is back and forth motion, there is no reason for it to be directional.
And you are doing that how? with a magic wand? Sure the relativistic mass of an object increases slightly as it accelerates, but this is small at any relevant speed, and it is an effect built in to momentum conservation under special relativity, so that doesn't get you anywhere.Quote
I already stated, by changing the effective mass of the electrons involved.If electrons can be made to intact with space time the efficiency of converting the photon frequency to space time thrust may not be dismal.
This is another one of those ideas that immediately brings up the question of how exactly you propose to do this, and why you think this could produce useful thrust.
No, what you just said is literally the exact opposite of what I said. Especially re-read where I added the bolding.QuoteI have explained this to you repeatedly: If you look at a photon reflecting off of a mirror from a variety of reference frames, you will see different results for the energy transfer and can find any answer you want from near 100% transfer of energy from the photon to the mirror, to frames where the mirror has high velocity towards the direction the photon is coming from, and the mirror transfers energy to the photon. All of these accurately describe the same event, and none of it is any different than photon rocket propulsion. (The basic kind without recycling, just a factor of 2 since it is an externally provided photon being reflected.) This is dictated by the principle of relativity, that the laws of physics do not depend on choice of inertial reference frame. The example with back holes only indicates the extreme amount of energy that is released in order to provide the high acceleration.
Good, so you agree that there can be efficient energy transfer from a photon to kinetic energy of a vehicle. This would effectively absorb up to 100% of the photons frequency to kinetic energy of a vehicle in a single collision. Much more efficient than propulsion by normal photons where almost all the energy resides entirely in the photon itself and no energy is transferred to the vehicle.
Different amounts of energy transfer in different reference frames is no different than noticing that if you are standing on your head you see objects falling up instead of down. The energy of the photon is different in different reference frames, because the frequency shifts thanks to the Lorentz transform. In frames where it transfers more energy, it had more energy to begin with, and also more momentum, but it loses some of the factor of 2 in the momentum transfer from the reflection, since it Doppler shifts upon reflection.
The actual frame invariant thing that defines the effective efficiency is the energy/momentum ratio of the photon, which is the same in all cases. The fact that any single instance of a photon reflecting off a mirror can have any energy transfer ratio you want just by picking a different, equally valid reference frame means that this metric is meaningless, no matter how much you insist on using it. -
#1273 by Bob012345 on 02 Aug, 2019 18:13
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[
No, what you just said is literally the exact opposite of what I said. Especially re-read where I added the bolding.QuoteI have explained this to you repeatedly: If you look at a photon reflecting off of a mirror from a variety of reference frames, you will see different results for the energy transfer and can find any answer you want from near 100% transfer of energy from the photon to the mirror, to frames where the mirror has high velocity towards the direction the photon is coming from, and the mirror transfers energy to the photon. All of these accurately describe the same event, and none of it is any different than photon rocket propulsion. (The basic kind without recycling, just a factor of 2 since it is an externally provided photon being reflected.) This is dictated by the principle of relativity, that the laws of physics do not depend on choice of inertial reference frame. The example with back holes only indicates the extreme amount of energy that is released in order to provide the high acceleration.
Good, so you agree that there can be efficient energy transfer from a photon to kinetic energy of a vehicle. This would effectively absorb up to 100% of the photons frequency to kinetic energy of a vehicle in a single collision. Much more efficient than propulsion by normal photons where almost all the energy resides entirely in the photon itself and no energy is transferred to the vehicle.
Different amounts of energy transfer in different reference frames is no different than noticing that if you are standing on your head you see objects falling up instead of down. The energy of the photon is different in different reference frames, because the frequency shifts thanks to the Lorentz transform. In frames where it transfers more energy, it had more energy to begin with, and also more momentum, but it loses some of the factor of 2 in the momentum transfer from the reflection, since it Doppler shifts upon reflection.
The actual frame invariant thing that defines the effective efficiency is the energy/momentum ratio of the photon, which is the same in all cases. The fact that any single instance of a photon reflecting off a mirror can have any energy transfer ratio you want just by picking a different, equally valid reference frame means that this metric is meaningless, no matter how much you insist on using it.
I'm not sure what you are trying to say? Are you saying no photon recycling scheme is worth doing no matter what? -
#1274 by meberbs on 02 Aug, 2019 18:44
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I'm not sure what you are trying to say? Are you saying no photon recycling scheme is worth doing no matter what?
I am not saying anything like that. Recycling photon rockets would work as demonstrated in the shared video, as long as you can deal with beam focus over long distances. For practical purposes, it would be best to generally anchor them to the moon, but then you are limited to accelerating away from the moon, which still has uses. (There are also some other potential applications though such as using a large LEO satellite as the momentum sink.)
Dustinthewind is also talking about other things including claims that a single reflection photon rocket is somehow more efficient when the mirror is moving at relativistic speeds, despite the fact that this is only a matter of perspective, and you can get any answer you want for the energy transfer by shifting reference frames, since any mirror is moving relativistically in some reference frame. -
#1275 by Bob012345 on 02 Aug, 2019 19:25
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I'm not sure what you are trying to say? Are you saying no photon recycling scheme is worth doing no matter what?
I am not saying anything like that. Recycling photon rockets would work as demonstrated in the shared video, as long as you can deal with beam focus over long distances. For practical purposes, it would be best to generally anchor them to the moon, but then you are limited to accelerating away from the moon, which still has uses. (There are also some other potential applications though such as using a large LEO satellite as the momentum sink.)
Dustinthewind is also talking about other things including claims that a single reflection photon rocket is somehow more efficient when the mirror is moving at relativistic speeds, despite the fact that this is only a matter of perspective, and you can get any answer you want for the energy transfer by shifting reference frames, since any mirror is moving relativistically in some reference frame.
Thanks. I see. Regarding relativistic moving mirrors, if the mirror is moving at virtually c wrt the beam source, it will convert nearly 100% of the beam energy into kinetic energy. Then, there will be virtually no reflected beam to get back to source where the other mirror is. If another observer moving at half c would say there is a reflected beam that gets back to the source, what if there is a bomb with a wavelength dependent trigger at the source? Some say it explodes, while some say it doesn't! Clearly, the event of the bomb exploding or not must be the same for all observers though at different times. The answer is that all observers would see that whatever their relative speed, the light is of such a frequency and the mirror is of such velocity that when the beam hits the mirror, it will be fully absorbed. In other words, they all see both different light characteristics and different mirror speeds but the same physics. So the two events of the light being absorbed and the bomb not exploding are universal to all observers. -
#1276 by meberbs on 02 Aug, 2019 23:34
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Thanks. I see. Regarding relativistic moving mirrors, if the mirror is moving at virtually c wrt the beam source, it will convert nearly 100% of the beam energy into kinetic energy. Then, there will be virtually no reflected beam to get back to source where the other mirror is. If another observer moving at half c would say there is a reflected beam that gets back to the source, what if there is a bomb with a wavelength dependent trigger at the source? Some say it explodes, while some say it doesn't! Clearly, the event of the bomb exploding or not must be the same for all observers though at different times. The answer is that all observers would see that whatever their relative speed, the light is of such a frequency and the mirror is of such velocity that when the beam hits the mirror, it will be fully absorbed. In other words, they all see both different light characteristics and different mirror speeds but the same physics. So the two events of the light being absorbed and the bomb not exploding are universal to all observers.
Close, but not quite.
Because of some combination of length contraction and time dilation, observers from different reference frames would disagree on the wavelength is required to trigger the bomb. Therefore if in whatever frame you like the observed "bomb trigger frequency" is equal to the frequency of the photon, than those things would be equal to each other in every frame. If any light is reflected at all, than there must be some light reflected in every frame, with the same number of photons but a different energy and frequency. Otherwise there could be no such thing as reflected light, and we know that mirrors exist. -
#1277 by Bob012345 on 02 Aug, 2019 23:47
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Thanks. I see. Regarding relativistic moving mirrors, if the mirror is moving at virtually c wrt the beam source, it will convert nearly 100% of the beam energy into kinetic energy. Then, there will be virtually no reflected beam to get back to source where the other mirror is. If another observer moving at half c would say there is a reflected beam that gets back to the source, what if there is a bomb with a wavelength dependent trigger at the source? Some say it explodes, while some say it doesn't! Clearly, the event of the bomb exploding or not must be the same for all observers though at different times. The answer is that all observers would see that whatever their relative speed, the light is of such a frequency and the mirror is of such velocity that when the beam hits the mirror, it will be fully absorbed. In other words, they all see both different light characteristics and different mirror speeds but the same physics. So the two events of the light being absorbed and the bomb not exploding are universal to all observers.
Close, but not quite.
Because of some combination of length contraction and time dilation, observers from different reference frames would disagree on the wavelength is required to trigger the bomb. Therefore if in whatever frame you like the observed "bomb trigger frequency" is equal to the frequency of the photon, than those things would be equal to each other in every frame. If any light is reflected at all, than there must be some light reflected in every frame, with the same number of photons but a different energy and frequency. Otherwise there could be no such thing as reflected light, and we know that mirrors exist.
I disagree. The wavelength that triggers the bomb was designed at a fixed value. It is invariant. Only that wavelength will trigger the bomb. Observers don't disagree about that. I think what you are missing is that it isn't the conditions as observed by an arbitrary viewer that matters, each one has to translate to the proper reference frame which is the reference frame where the bomb is. Then they will all agree on the frequency. -
#1278 by Monomorphic on 03 Aug, 2019 00:15
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This is the new hanging torsional pendulum that I plan on using to test a custom built liquid metal RF coax connection. After that, with some structural and damping modifications, I can also resume testing emdrives again.
In this image, the balance is configured to have the same torsional spring rate and oscillation period as the Fullerton-style torsional pendulum I have also built. This is so I can test the differences between hanging pendulums and dual flexure bearing pendulums.
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#1279 by meberbs on 03 Aug, 2019 00:26
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I disagree. The wavelength that triggers the bomb was designed at a fixed value. It is invariant. Only that wavelength will trigger the bomb. Observers don't disagree about that. I think what you are missing is that it isn't the conditions as observed by an arbitrary viewer that matters, each one has to translate to the proper reference frame which is the reference frame where the bomb is. Then they will all agree on the frequency.
All of the observers can use the Lorentz transformation and do the calculation in the rest frame of the bomb, and compare to the frequency of the the light in the rest frame of the bomb, but that is missing the point.
You can do the calculations in any inertial frame you want, and you will always get that the bomb trigger frequency is the same as the frequency of the light in that frame. Whether or not the bomb explodes is a relativistic invariant. The frequency of any given photon is not an invariant. Similarly, the physical size of the bomb, and frequency of reference oscillators inside the bomb, etc are also not invariant.