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I'm a prisoner of SFN protocol? Well anyway just to clear up re broken links, they both work fine for me. Maybe try another browser. And re 'looking for alternatives in crackpot nests like vixra.org.', you misrepresent the situation. I made a comment there directed to someone who has published articles in respected astrophysical journals. Try not to tar everything with the same brush. Now, unless you wish to push this line of talk, there has been a hint to return to the main EHT topic.

I have made my position sufficiently clear. And you have now made your hostile attitude clear. End of conversation.

I have elsewhere at SFN contributed to discussion of in particular Anatoly Svidzinsky's Vector Theory of Gravity: https://www.scienceforums.net/topic/117068-vector-theory-of-gravity/?do=findComment&comment=1081799 and onwards there. Making it clear I have no commitment to that theory, but noted it does tick a number of plus boxes GR cannot. Self-consistency for any theory of gravity imo requires at least two characteristics absent in GR: 1: Exponential form for gravitational redshift for a spherically symmetric static central mass. Recently my thinking has shifted a little there, as per my comments here: https://vixra.org/abs/1808.0642 At any rate, such exponential form, exact or as limiting case, forbids existence of EH's. 2: Intrinsic isotropy of exterior metric for a spherically symmetric static central mass (afaik my unique finding). Which again forbids existence of EH's. To enlarge on above is getting way off topic. And not interested anytime soon starting or participating in a time-consuming thread going further there. I had prepared a point-by-point rebuttal to a hostile posting by Strange, but now find it has been mysteriously vanished. So be it. (Hope this and last post doesn't get to be merged, which annoyance has become my routine experience at SFN.) Uh oh - it got merged. Sigh.

Whichever theory of gravity eventually proves true. Something bleeding obvious from preceding context I would have thought! Evidently whoever red carded me earlier here is not up to justifying it - as i requested be done. The trouble with anonymity - too easy.

Indeed - with that in red agreed. I tire of endless corrections. With you the cycle is endless. Time will eventually tell which theory is correct.

There you go again - claiming certainty re validation of GR/BH's. Anyone with an ounce of caution would not use such commitment words. And btw the logical statement would have it "GR, and BH's as an extension" and not the reverse as you incorrectly worded it. Not just GR but various other, rival theories, have also 'passed another crucial test'. Something tacitly denied by the hyped pro-GR rhetoric. I don't need resorting to bold text to emphasize that point.

Have no knowledge re "Rosalind Franklins and Caroline Herschels of the world.", but presumably that relates in some way to the 'feminist-empowerment/sexist-bias' angle being so aggressively pushed throughout not just academia but (Western)society in general. Whatever - it remains the case the absurd claim of 'single-handedly accomplishing' being attributed to ANY one individual re EHT preliminary results is unforgivable tripe. There is no valid excuse. Thanks for clarifying you are not the 'red carder'.

That much in red is obvious, given the remainder of that passage completely misses the standard - yes standard - point I have repeatedly made about sungularities, or conjectured 'quantum/Planck level' singularity-like entities, lying in the infinite future in standard GR. They don't exist now - not from any external observers pov. Savvy? One 'modifier' I failed to mention in an earlier post was 'Hawking radiation'. Another artifact of horizon existent theories of gravity, which if real logically disallows any singularity anyway. All such bizarre conundrums are absent from certain, inherently more self-consistent horizonless theories of gravity. So sorry. I had assumed given you are a resident of a Sydney NSW Australia suburb, you would be loyal to your locally brewed beer. My apologies! That comment in red betrays your occasional, inconsistent claim to not be wedded to GR as THE classical-level theory of gravity. My, someone here decided to 'red card' my earlier (annoyingly combined) post: . Whoever you are, please have the courage and decency to step forward, here in this thread, and clearly explain your presumably rational and objective reason(s) for doing so!

?????? A hypothesized spacetime quantization 'rescuing' classical GR from 'actual singularity' has NO bearing on that in either case such an 'extreme object' is, purely owing to existence of an EH, an event in the infinite future. Raise a Tooheys Blue to a blurry image exhibiting only the most basic features common to any generic metric theory of gravity? Umm...no. It is a fantastic technical achievement, so maybe that alone is a good enough excuse for you to keep swilling beer. But I shall reserve celebrations for the time - maybe not in our lifetime, when a final theory has been confirmed beyond any reasonable doubt. Via multiple observational methods. And GW 'astronomy' looks to be imo the best approach by far. 'Single-handedly responsible'?! This is a sad example of what I meant earlier by hype being rife. The many able-bodied physicists and engineers working tirelessly on the huge collaboration that is EHT would be perfectly justified in feeling slighted indeed insulted by that absurd claim.

All the previous posts (which take as a given the correctness of GR or similar theories where horizons exist) speculating about 'the singularity', fail to note that in such classical theories 'the singularity' is from any exterior observer's perspective, an event that occurs in the infinite future! There is NO existing singularity. Unless one wishes to take the hypothetical in-faller pov - where the exterior universe becomes infinitely old at the point of passing EH! Of course there now exists a menagerie of more exotic refinements/extensions/modifications. Where for instance the in-faller may be fried at a firewall horizon etc. and never makes it further in because there is no further in. Or other exotic possibilities like 'fireworks' 'bounces'. Take your pick. For the enthusiast salivating that this EHT image of shadow of M87 central object has 'proven' BH's thus 'proven' GR - sorry, it has done no such thing. Any half-way viable gravity theory will predict a photon-sphere. There is far more observational data needed and refining of that data before any kind of confident winnowing down of currently viable theories will be possible. Hype - nearly all of it pro GR, is rife. Settle down and prepare for a lengthy wait.

Very good. Imagination is necessary if anyone want's to be creative/innovative. However it needs partnering with a solid grasp of the established fundamentals in a chosen field. Keep searching - and learning!

I truly hope so - good news if it stays that way! You deserve an A for ingenuity. but that doesn't translate into success. When the two projectiles mutually spin each other down, there is initially simply a conversion of rotational KE to thermal energy. So the total mass-energy hence also momentum is constant. Of course there follows radiation of heat into the surrounds, which owing to the forward motion, imparts a linear momentum to the surrounds via an overall Doppler shift enhancement of photon frequencies in the direction of motion. So although the projectiles have lost mass, the combined momentum of cooling projectiles plus surrounds owing to radiated heat is constant. A final deceleration of projectiles merely net cancels out the initial impulse given to them at the start. In summary, your system simply trades rotational KE for thermal energy, which partially 'leaks' into the environment, imparting just enough momentum there to fully account for the reduced momentum in the combined, non-rotating projectiles. Bottom line - still no propellantless propulsion. Bummer.

Coriolis force is 'fictitious' in the sense that it is interpreted differently depending on one being in an accelerated or non-accelerated reference frame, but has very real dynamical effects regardless. However on thinking it over less reflexively, now realize it's not Coriolis but the centrifugal reaction forces generated by the carousel motion that 'pushes' and 'pulls' on any given mass element in a wheel. Which is experienced as periodically varying stresses in the wheel rims. This will cover for swansont's post also: Place a paint spot on the rim of any given wheel. Does the spot remain stationary or move in an overall helical path? Obviously the latter. That paint spot is associated with a local element of wheel rim mass. Spot moves - so also a mass element adjacent to the spot. No brainer. By analogy, consider a circular current loop, carried within a conducting wire. At any given fixed location along the wire, the current is unchanging. But that current is the result of individual charges in constant motion along the wire. Single out any given conduction charge and follow it. It's obviously not fixed at one location. To sort of complete the analogy, imagine the conducting wire has a cross-sectional area that varies around the loop. Where the section is smallest, speed of charges there must be greater than where the section is larger, in order that the current remains constant in magnitude everywhere. So although the current is constant everywhere, individual charges, which collectively form the loop current, have to undergo acceleration and deceleration during a complete circuit around the loop. The analogy is not perfect since in the wheels case, the wheel rim 'mass current' itself is not uniform but greatest at the outside of the rims (your speed A1's). Moral - follow a given element of mass in a given wheel. It eventually traces out a closed helical path that simply keeps repeating. In fact it's only necessary to consider the helical path through one complete wheel cycle. There is generally acceleration/deceleration along that path, but no change from one cycle to another. Always the velocity of a given mass element returns to the same value at a given angular location wrt the given wheel. Momentum circulates - hence no net dp/dt acting anywhere. In particular for you, there can be no net dp/dt along the carousel axis. Rockets get round this via expulsion of mass.

Look up Coriolis force - and think about that some. Oh, and that mass element is then 'pulled' back down to a lower speed - and so on cyclically. Nothing changes over a complete cycle. If you think otherwise, try and prove using maths based on relativistic dynamics. Good luck!

Still didn't answer my question. But I can hazard a guess and assume your 'up' is indeed directed along the carousel spin axis. What you keep failing to see is that in order to gain that extra speed thus naively computed 'relativistic mass' gain at outer rim locations, any given element of mass in a wheel rim had to be 'pushed' somehow to achieve the extra speed there. Which implies a back reaction force on whatever did the pushing. Newton's 3rd law. I believe that has been mentioned before - numbers of times in fact. Every wheel rim mass element undergoes an overall helical motion, and depending on the exact ratio between wheel and carousel angular speeds, will sooner or later form a closed path. Especially if the carousel base is firmly anchored to terra firma, you must explain how closed helical paths can possibly generate a time-averaged net axial thrust. Think about that some. Must go.

See, from the start your diagrams vs commentary create confusion since in both diagrams the carousel axis is shown horizontal, whereas your commentary referencing 'up' only makes sense if 'up' is really 'sideways/horizontal' as per illustrations. Clarify that please. Also, your 'directions A' and 'directions B' are totally non-standard notation. Regardless of which way your 'up' is relative to carousel axis, maximum 'relativistic mass' in each convected wheel rotating about the carousel axis, lies in the plane normal to that axis and which bisects each wheel. Thus any net momentum (for now ignoring my earlier input re role of stress!) in each convected wheel is directed along the carousel axis. There is zero net rate-of-change of momentum along that axis by reason of the symmetries of wheel circular motions. Hence no force along that axis. The symmetries of rim motions guarantees no net axial force can exist, given we are talking about a steady-state situation. Your whole thinking is that the carousel assembly will accelerate parallel to the carousel rotation axis - yes? Which cannot happen. If that is not blindingly obvious by now, you have a real problem.

From earlier post https://www.scienceforums.net/topic/118458-propellant-less-space-engine/?do=findComment&comment=1098095 "...Since F = dp/dt, and there is no change in net p in a steady state. Hence no steady propulsive force is ever possible..." Evidently you reject that for some unstated reason. Why? At very best, your arrangement may carry a tiny amount of 'hidden momentum' implying a very tiny drift velocity has been induced. Generated - just maybe - only during build-up phase when angular velocities are changing. Nothing more beyond that is logically conceivable, and most would insist even that much is impossible. Time to start listening and give imagination a vacation.

Uh huh. Well regarding your unbalanced wheel spinning/wiggling in space, is it not obvious that all one has is rotation about a common center of mass? Going back to your more interesting 'doughnut Mk II', a basic fact to have to consider is the universal validity of Newton's 3rd law. Action & reaction are always exactly paired - sometimes statically, sometimes dynamically. Every now and then even 'experts' claim violations of that 3rd law, but that's only an indication they have an artificially restricted definition/application. All considered, there can logically never be a violation of that 3rd law - properly and comprehensibly applied. Must go.

Did you read and try and absorb the content of my last post?

OK with the configuration as shown in Wheel_Layout.pdf, there is no variation in angular speed about 'directions A' - unlike my impression of the earlier case with single concentrated masses on each wheel rim. You are relying on the combined, orthogonal velocities, of inner wheel rims about 'A directions', plus convective carousel motion of the wheels in 'B' direction(s). That's a fairly messy situation to evaluate as it requires integrating over the appropriate components of relativistic momentum acting along carousel rotation axis. Not so straightforward as you may think. One immediate fact to consider is that even if there is a net momentum along the carousel rotation axis by that integration, it could only give rise to an initial impulse during the build up phase to a final steady state motion. Since F = dp/dt, and there is no change in net p in a steady state. Hence no steady propulsive force is ever possible - at best a tiny drift speed conceivably has been induced. But even that assumes there has been no back-reaction going on during speed build up phase that exactly cancels any such assumed net linear momentum residing within the wheels assembly per se. Newton's 3rd law has to be respected in all this! You will have to do the arduous relativistic formulae sums and determine analytically the actual case one way or the other. I wouldn't attempt it as there are just too many factors to consider in total. The case of rotating pendulum I proposed earlier is much more tractable though still not easy. Attempting that scenario may give you some valuable insights. [PS: there is something else of interest going on akin to your latest setup that is a real head scratcher. Sorry won't say what but investigated it many years ago and never found a conventional resolution. I add this only to have it on the record, in case there is any chance of a claim down the track that I 'stole or at least got initial inspiration from someone else's idea'. Can say this much - it relates to the concepts of hidden momentum (real enough), and so-called 'stored field momentum' (doubtful imo). Look them both up - it will doubtlessly broaden your understanding. I believe your latest incarnation likely does involve 'hidden momentum' residing in the wheels assemblage.]

Ah ok then it was a misunderstanding as I had no idea about a 5 post initial limit. All get on that score. Last part first. No - as I explained in initial response post. The 'spring energy' contribution from stress is of an entirely different character and magnitude to that of stress as component(s) of the stress-energy-momentum tensor in GR. See the articles I linked to last post. To avoid confusion as to what is meant by 'up on outside edge' vs 'down on inside edge' etc., use the carousel axis (lets label it z) as a spatial reference. Hence 'up on outside edge means '+z velocity'? etc. At any rate I agree with other poster here that your arrangement is symmetric and no wobble can occur for that reason alone. Try a simplest case. Just a single 'inner wheel' best thought of as a pendulum - mass on a light but rigid arm free to pivot about a shaft whose axis is oriented normal to Earth's gravity. Give the mass a sufficient initial boost that it rotates continually about it's axis, but with an obvious periodic variation in angular speed owing to gravity. Assume negligible 'wobble' of the shaft which is housed in a very rigid support frame itself firmly attached to terra firma. We know that based solely on Newtonian physics, the net vertical impulse through one complete cycle must equal just the product of pendulum mass m and period T. Your task is to apply relativistic corrections to the mass and speed, and determine precisely how much the impulse per cycle is different to Newtonian case. It will be greater for the obvious reason that 'relativistic mass' has increased over the rest mass, and further because the period T will be greater (less average speed than for Newtonian case). What is relevant is whether there is an additional 'dynamical component' that would correspond to your notion of propellantless propulsion. In other words, if the properly computed net impulse per cycle differs from m'.T, where m' is the averaged 'relativistic mass' gamma.m. If it is, then you will realize that stress in the pendulum arm is probably a crucial missing factor.

'Senior' as designation doesn't take long to accrue here. Point is, you could have said something. Even a simple acknowledgement. Anyway, re your doughnut arrangement: as has been pointed out, your illustration is symmetric wrt dynamics. I took it you really meant an arrangement where each inner wheel had the same rotational speed about it's axis as that of wheel(s) about carousel axis, but where phasing of weights led to maximal speed at a single angular location wrt carousel axis. Only then could one even hope for a net force or rather impulse. Your diagram needs amending accordingly. But it won't eventuate even then, if all factors are considered: https://arxiv.org/abs/gr-qc/0510041v1 https://arxiv.org/abs/physics/0609144 There are consistency issues with stress as source of gravity/inertial mass, but it probably works out 'as normally expected' for your scenario.

From John Lowe's first post: "...but if somebody could at least explain what is wrong with my logic I would appreciate it..." Actually, you seem quite unappreciative. Why have you totally ignored my attempt to point out basic flaws in your reasoning? Obsessed? Totally sure you are right? Unwilling or unable to apply the formulae in article linked to? Not up to doing your own search for role of stress in relativistic physics? Or just ignorant maybe?

You deserve more than just skepticism void of some level of detailed physical reasoning behind such. Regarding your 1st idea, it's enough to know that absence of any axial force gaurantees axial i.e. linear momentum is constant. But it can be established another way. Applying a mid-flight spin down torque means applying a purely transverse force (seen from the 'stationary' gun barrel frame) on each mass element in the ball not lying eaxactly on the spin axis. How that can be done in practice we don't worry about here! That transverse force is acting on a mass element at some finite radius from the spin axis, thus having both transverse and axial motion. It's a fact of relativistic transformation laws that acceleration and force are not collinear if force and velocity are not collinear. You guessed it - transverse deceleration i.e. spin down is also accompanied by an axial acceleration that exactly maintains linear momentum constant. I'm not going to work through the tedious specifics for a worked example confirming that claim, but will point you to an article, which YOU can then use to verify that momentum conservation holds: https://arxiv.org/abs/1806.08680 Regarding your 2nd example, you need to be aware that stress, both as cause of elastic energy and stress 'all by itself', is a source of inertial mass in relativity. Unlike the generally much smaller elastic energy contribution, which is a quadratic function of stress, inertial mass owing to stress 'all by itself' changes sign with a change of sign of stress. At the locations where the masses have maximum KE thus 'relativistic mass', there is also maximum tensile (negative!) inertial mass owing to tension in the spokes holding each mass. Again, I won't bother computing the competing effects, but suggest you ponder the situation more fully. What looks cut and dried initially is actually fairly complex.

I just noticed this post from a casual random read. It's wrong. Squeezing down a cavity with implicitly notionally perfectly reflecting walls means work is being done against radiation pressure that naturally resists any shrinkage. Adiabatic process. This in turn MUST result in an increase in photon energy - if net system conservation of energy is to be maintained. The resolution fairly obviously involves that shrinkage requires an initial inward acceleration of wall motions. Relative wall-photon momentum exchange therefore increases over time and that implies an increase in (center-of-system-energy) photon frequency. Invoking photon absorption as 'resolution' is an appeal to material properties (finite conductivity) which cannot be fundamental to the basic physics involved. [PS: But there is still the need to explain photon energy increase during a more-or-less constant inward wall speed phase. One cannot appeal to an increase in per-impact bullet-like photon-wall momentum exchange. Only to a change in the overall cavity mode pattern/field intensity. Which would be particularly evident if the notional photon wavelength is comparable to cavity size. Especially if it gets down to the limit of a fundamental cavity mode only being present, then the picture basically reduces to one of field/wall-current coupling.] [Even further, it will all depend on precisely HOW the cavity is shrunk for a given mode pattern. For instance, shrinkage along only the E field axis of a rectangular cavity in fundamental TE_010 mode will involve negative work being done on the cavity hence a reduction in field energy. Whereas shrinkage only normal to that axis (against magnetic outward pressure) increases internal field energy.]