Herbert Dingle's Unanswered Question

ON THE ELECTRODYNAMICS OF MOVING BODIES, A. Einstein, 1905: "From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by tv^2/2c^2 (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B."

SCIENCE AT THE CROSSROADS, Herbert Dingle, p.27: "According to the special relativity theory, as expounded by Einstein in his original paper, two similar, regularly-running clocks, A and B, in uniform relative motion, must work at different rates. (...) How is the slower-working clock distinguished?"

Einsteinians, how is the slower-working clock distinguished?

Pentcho Valev

    It has been many since I read Paul Davies' book Super Force. Hopefully I remember correctly. In that book he remarked about Herbert Dingle. Paul Davies attended Oxford but only after Herbert Dingle was gone. Paul Davies remarked in his book something close to saying that maybe it was best that they didn't meet. Paul Davies should not have made that remark. His book Super Force was a wild swing in the dark. Herbert Dingle deserves respect. Paul Davies deserves respect. But right is right and that hasn't yet been conclusively determined.

    James Putnam

    Dingle's question is rhetorical - the slower-working clock cannot be distinguished on the basis of Einstein's 1905 postulates alone. The postulates entail that, as judged from the respective system, either clock runs slower than the other. That is, for an observer in the moving clock's system, the stationary clock at B lags behind the moving clock; for a stationary observer at B, the moving clock lags behind the stationary clock at B.

    So Einstein's famous "moving clocks run slow" and "travel into the future is possible" are based on two flaws. Initially Einstein advanced his false constant-speed-of-light postulate, which allowed him to validly deduce that:

    Moving clocks run slow, as judged from the stationary system.

    Then he illegitimately dropped the last part of the conclusion and informed the gullible world that:

    Moving clocks run slow, that is, travel into the future is possible.

    Pentcho Valev

    Out of what is bad, good can come out. Repetitive posts are bad, but thanks Pentcho for pointing me to a free copy of Herbert Dingle's book. It is a master piece I recommend to the FQXi membership. I also made reference to it in my reply to Tejinder Singh on his essay thread.

    19 days later
    4 days later

    Einstein's Nonexistent Space-Time

    "Wherever you may be on the space-time continuum, it's time to celebrate!"

    It would be difficult to be anywhere on the space-time continuum - it does not exist:

    Nima Arkani-Hamed 06:11 : "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."

    WHAT SCIENTIFIC IDEA IS READY FOR RETIREMENT? Steve Giddingss: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... (...) The apparent need to retire classical spacetime as a fundamental concept is profound..."

    "...says John Norton, a philosopher based at the University of Pittsburgh, Pennsylvania. Norton is hesitant to express it, but his instinct - and the consensus in physics - seems to be that space and time exist on their own. The trouble with this idea, though, is that it doesn't sit well with relativity, which describes space-time as a malleable fabric whose geometry can be changed by the gravity of stars, planets and matter."

    "And by making the clock's tick relative - what happens simultaneously for one observer might seem sequential to another - Einstein's theory of special relativity not only destroyed any notion of absolute time but made time equivalent to a dimension in space: the future is already out there waiting for us; we just can't see it until we get there. This view is a logical and metaphysical dead end, says Smolin."

    "Was Einstein wrong? At least in his understanding of time, Smolin argues, the great theorist of relativity was dead wrong. What is worse, by firmly enshrining his error in scientific orthodoxy, Einstein trapped his successors in insoluble dilemmas..."

    Why is Einstein's space-time nonexistent? Because it is an absurd consequence of Einstein's assumption (postulate) that the speed of light is constant. In fact the speed of light is variable. When an observer starts moving towards a light source with (small) speed v, the frequency he measures shifts from f=c/λ to f'=(c+v)/λ, where c is the speed of the waves relative to a stationary observer and λ is the wavelength.

    Question: Why does the frequency shift from f=c/λ to f'=(c+v)/λ?

    Answer 1 (fatal for Einstein's relativity): Because the speed of the waves relative to the observer shifts from c to c'=c+v (that is, relative to the observer, the speed of the light is now greater than c).

    Answer 2 (possibly saving Einstein's relativity): Because...

    There is no reasonable statement that could become Answer 2:

    "Doppler effect - when an observer moves towards a stationary source. ...the velocity of the wave relative to the observer is faster than that when it is still."

    "Thus, the moving observer sees a wave possessing the same wavelength (...) but a different frequency (...) to that seen by the stationary observer."

    "We will focus on sound waves in describing the Doppler effect, but it works for other waves too. (...) Let's say you, the observer, now move toward the source with velocity vO. You encounter more waves per unit time than you did before. Relative to you, the waves travel at a higher speed: v'=v+vO. The frequency of the waves you detect is higher, and is given by: f'=v'/λ=(v+vO)/λ."

    Clever Einsteinians have always known that the speed of light varies with the speed of the observer. Here is an implicit confession:

    Albert Einstein Institute: "The frequency of a wave-like signal - such as sound or light - depends on the movement of the sender and of the receiver. This is known as the Doppler effect. (...) Here is an animation of the receiver moving towards the source:

    stationary receiver

    moving receiver

    By observing the two indicator lights, you can see for yourself that, once more, there is a blue-shift - the pulse frequency measured at the receiver is somewhat higher than the frequency with which the pulses are sent out. This time, the distances between subsequent pulses are not affected, but still there is a frequency shift: As the receiver moves towards each pulse, the time until pulse and receiver meet up is shortened. In this particular animation, which has the receiver moving towards the source at one third the speed of the pulses themselves, four pulses are received in the time it takes the source to emit three pulses."

    _______________________________________

    [end of quotation]

    Since "the distances between subsequent pulses are not affected", and since "four pulses are received in the time it takes the source to emit three pulses", the speed of the light as measured by the receiver (observer) is:

    c' = 4d/t = (4/3)(3d/t) = (4/3)c

    where d is the distance between subsequent pulses, t is "the time it takes the source to emit three pulses", and c=3d/t is the initial speed of the light (as measured by the source).

    Clearly the speed of light (relative to the observer) varies with the speed of the observer, as predicted by Newton's emission theory of light and in violation of Einstein's relativity.

    Pentcho Valev

      Pentcho, All,

      if space-time doesn't exist as those above quoted people suspect, then there still has to be an explanation for relativity and non simultaneity of events. They are explicable if what exists instead of the space-time continuum is potential sensory data spreading out from its (the data's)source in uni-temporal(one time everywhere) space. That sort of data when received by an observer is fabricated into space-time output as it contains data that has taken different lengths of time to arrive at the observer, giving temporal spread as well as spatial spread in the output manifestation.

      To say space-time doesn't exist may be going to far.For example looking at a photograph, of a group of people in the foreground and mountains in the distance -it is a space-time image. The light from the mountains took longer to reach the camera than light from the people.It can be identified as an emergent reality, fabricated from data, and not merely part of the foundational external reality, as are the ink and paper. I really think that if you are going to pull the rug away there needs to be solid ground below, that's what the explanatory framework I continue to describe provides.

      "Baumgarte began by discussing special relativity, which Einstein developed, 10 years earlier, in 1905, while he was employed as a patent officer in Bern, Switzerland. Special relativity is based on the observation that the speed of light is always the same, independently of who measures it, or how fast the source of the light is moving with respect to the observer. Einstein demonstrated that as an immediate consequence, space and time can no longer be independent, but should rather be considered a new joint entity called "spacetime."

      There was no such "observation". Rather, all reliable evidence shows that the speed of light is variable, as predicted by Newton's emission theory of light:

      Introduction to Special Relativity, James H. Smith, p. 42: "We must emphasize that at the time Einstein proposed it [his second postulate], there was no direct experimental evidence whatever for the speed of light being independent of the speed of its source."

      "Does the speed of light depend on the speed of its source? Before formulating his theory of special relativity, Albert Einstein spent a few years trying to formulate a theory in which the speed of light depends on its source, just like all material projectiles. Likewise, Walter Ritz outlined such a theory, where none of the peculiar effects of Einstein's relativity would hold. By 1913 most physicists abandoned such efforts, accepting the postulate of the constancy of the speed of light. Yet five decades later all the evidence that had been said to prove that the speed of light is independent of its source had been found to be defective."

      "These efforts were long misled by an exaggeration of the importance of one experiment, the Michelson-Morley experiment, even though Einstein later had trouble recalling if he even knew of the experiment prior to his 1905 paper. This one experiment, in isolation, has little force. Its null result happened to be fully compatible with Newton's own emission theory of light. Located in the context of late 19th century electrodynamics when ether-based, wave theories of light predominated, however, it presented a serious problem that exercised the greatest theoretician of the day."

      "In addition to his work as editor of the Einstein papers in finding source material, Stachel assembled the many small clues that reveal Einstein's serious consideration of an emission theory of light; and he gave us the crucial insight that Einstein regarded the Michelson-Morley experiment as evidence for the principle of relativity, whereas later writers almost universally use it as support for the light postulate of special relativity. Even today, this point needs emphasis. The Michelson-Morley experiment is fully compatible with an emission theory of light that CONTRADICTS THE LIGHT POSTULATE."

      "Relativity and Its Roots" by Banesh Hoffmann, p.92: "There are various remarks to be made about this second principle. For instance, if it is so obvious, how could it turn out to be part of a revolution - especially when the first principle is also a natural one? Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether. If it was so obvious, though, why did he need to state it as a principle? Because, having taken from the idea of light waves in the ether the one aspect that he needed, he declared early in his paper, to quote his own words, that "the introduction of a 'luminiferous ether' will prove to be superfluous."

      Albert Einstein Institute: "One of the three classical tests for general relativity is the gravitational redshift of light or other forms of electromagnetic radiation. However, in contrast to the other two tests - the gravitational deflection of light and the relativistic perihelion shift -, you do not need general relativity to derive the correct prediction for the gravitational redshift. A combination of Newtonian gravity, a particle theory of light, and the weak equivalence principle (gravitating mass equals inertial mass) suffices. (...) The gravitational redshift was first measured on earth in 1960-65 by Pound, Rebka, and Snider at Harvard University..."

      Richard Feynman, "QED: The strange theory of light and matter", p. 15: "I want to emphasize that light comes in this form - particles. It is very important to know that light behaves like particles, especially for those of you who have gone to school, where you probably learned something about light behaving like waves. I'm telling you the way it does behave - like particles. You might say that it's just the photomultiplier that detects light as particles, but no, every instrument that has been designed to be sensitive enough to detect weak light has always ended up discovering the same thing: light is made of particles."

      Pentcho Valev

      This is fun to read all of these old articles. Smolin is getting very close to the truth about time, but he is still blinded like many others by our overwhelming intuition of space. It is very interesting to see him struggle so close to a realization of time.

      For some reason, he does not mention the thousands of millisecond pulsars that are the neutron star timekeepers of the heavens and the first dimension of time. He also does not mention that all of these pulsars decay with an average of 0.255 ppb/yr, which is the second dimension of time and the decay of the universe that drives all force.

      The arrow of time is implicit in a decaying universe and the galaxies stay together without dark matter and those pesky matter accretions are just the boson destiny of all matter and are no longer mysterious singularities.

      Minkowski space-time: a glorious non-entity, Harvey Brown and Oliver Pooley: "What has been shown is that rods and clocks must behave in quite particular ways in order for the two postulates to be true together. But this hardly amounts to an explanation of such behaviour. Rather things go the other way around. It is because rods and clocks behave as they do, in a way that is consistent with the relativity principle, that light is measured to have the same speed in each inertial frame."

      But this is a cosmic conspiracy of the highest order, isn't it? Neil deGrasse Tyson and Brian Greene wholeheartedly agree:

      Neil deGrasse Tyson: "If everyone, everywhere and at all times, is to measure the same speed for the beam from your imaginary spacecraft, a number of things have to happen. First of all, as the speed of your spacecraft increases, the length of everything - you, your measuring devices, your spacecraft - shortens in the direction of motion, as seen by everyone else. Furthermore, your own time slows down exactly enough so that when you haul out your newly shortened yardstick, you are guaranteed to be duped into measuring the same old constant value for the speed of light. What we have here is a COSMIC CONSPIRACY OF THE HIGHEST ORDER."

      Brian Greene: "If space and time did not behave this way, the speed of light would not be constant and would depend on the observer's state of motion. But it is constant; space and time do behave this way. Space and time adjust themselves in an exactly compensating manner so that observations of light's speed yield the same result, regardless of the observer's velocity."

      Pentcho Valev

      It isn't a cosmic conspiracy at all -its just people not telling the difference between what is seen, the insubstantial output of sensory data processing, and, what exists externally and independently, the unobserved substantial reality, ( and source of EM data.)

      It isn't 'concrete' Objects that are shortening but the images produced from the received EM data.

      Muddling insubstantial Image manifestations with actualized substantial Objects is a category error as the two kinds of 'object', as described, belong to different categories of object belonging to different categories of reality.

      Not a cosmic conspiracy but possibly a human one. Heaven only helps those who help themselves.

      If a professor of physics and mathematics and author is unaware that the observer's state of motion affects the speed of light in Pulsar timing observations, Lunar laser ranging, Global Positioning System, the measurement of the otherwise largely isotropic CMBR, in all of which "space and time DID NOT not adjust themselves in an exactly compensating manner so that observations of light's speed yield the same result", this can only be either a human conspiracy or a result of brain washing on a very large scale.

      For a report detailing possibility of conspiracy, see 95 Years of Criticism of

      the Special Theory of Relativity

      For an example of possible brain washing, see my recent exchanges with Armin Nikkah Shirazi in the current essay contest. Armin is the author of the 'photon existence paradox', where going by what Brian Greene says "Each of us carries our own clock, our own monitor of the passage of time...", if a photon carries its own clock and we are told that because it travels at the speed of light clocks don't run for photons, then it means the time of its emission (birth) is the same as the time for its absorption (death), how then can photon exist? Despite formulating this paradox and admitting in evidence that an observer can influence and delay or hasten light arrival times by moving away from or towards incoming light contrary to Lorentz invariance, Armin still upholds special relativity as correct.

      Lastly, if "observations of light's speed yield the same result, regardless of the observer's velocity", what then is the observer's velocity, v doing in the Lorentz transformation equations since observations are regardless of it? You claim something is irrelevant in an equation, yet you put that parameter in the equation to have a non-zero value. Is this an example of Truth or Trick as per the theme of this years essay?

      Akinbo

      Pentcho, I see another example of brainwashing in your exchange with Lawrence on his Essay forum. After providing the reference of reduced light speed IN VACUUM, he waves this aside as having nothing to do with special relativity, saying "it is a quantum effect".

      However, in claiming that a postulate is UNIVERSAL, should its applicability not include the quantum realm? How can quantum theory then be unifiable with classical physics if already there is that bone of contention between them, resolution of which must inevitably lead to the death of one of the two theories, if not both?

      I just came across this example of brainwashing and felt like pointing it out.

      Akinbo

      Akinbo,

      Einsteinians' reaction to the discovery that the speed of light IN A VACUUM is not constant (published in Science) is an example of brainwashing indeed but a better qualification is "crimestop":

      "Crimestop means the faculty of stopping short, as though by instinct, at the threshold of any dangerous thought. It includes the power of not grasping analogies, of failing to perceive logical errors, of misunderstanding the simplest arguments if they are inimical to Ingsoc, and of being bored or repelled by any train of thought which is capable of leading in a heretical direction. Crimestop, in short, means protective stupidity."

      Pentcho Valev

      Hi Akinbo,

      I doubt it is even a human conspiracy.

      you wrote if "observations of light's speed yield the same result, regardless of the observer's velocity", what then is the observer's velocity, v doing in the Lorentz transformation equations since observations are regardless of it? You claim something is irrelevant in an equation, yet you put that parameter in the equation to have a non-zero value. Is this an example of Truth or Trick as per the theme of this years essay?"

      The transformation shows what would be observed, the manifestation. What is important in calculating that (and therefore included) is the observer's relationship to the potential sensory data carried by the EM radiation, not the EM radiation itself. As how it is intercepted affects what data is received when and thus the appearance of the processed output.

      Georgina,

      The Object reality-Image reality method of analysis is useful but is not the conventional way of arriving at dynamical transformations. There are two candidates, one is the Galilean transformation/ relativity, the other is the Lorentzian transformation/ relativity. Generally, I think your method falls under Galilean relativity. If it does not, please clarify.

      In Lorentz transformation, i.e. Special relativity, the observer's velocity has no influence on the manifestation/ outcome or output data as you like to call it.

      But if what you mean is that the observer's velocity interacts with the input data in such a way as to make the processed output data/ manifestation unchanged, then I see what you mean. However, you must explain why in some cases the observer's relationship to the potential sensory data carried by the EM radiation, has no influence on the appearance of the processed output like in the Michelson-Morley experiment, while in other experimental observations, the observer's relationship to the potential sensory data carried by the EM radiation, HAS influence on the appearance of the processed output, like in Pulsar timing measurements, the GPS, the CMBR, etc that I mentioned earlier.

      After much thought, I believe overall Galilean relativity is king.

      Regards,

      Akinbo

      Akinbo, All,

      Galilaean invariance /Newtonian relativity is about substantial objects existing in absolute space. I have seen that described as infinitely many universal sized reference frames. There is also a universal or absolute time , that is what I call uni-temporal(the same time everywhere) passage of time . Whereas Einstein's relativity is dealing with manifestations produced from data carried by light. The emergent reality. That's why the speed of light becomes important. Each inertial frame has its own time as that is what is seen. An observer looking at the clock in another's frame will see it show a different time from his own clock.

      Both kinds of relativity fit within the explanatory framework I have set out because one is dealing with the substantial Object reality and the other the insubstantial Image reality. Both are necessary in a complete description of the entirety of reality. It is not that only one is correct and the other is false. Confusing the two types of reality causes all kinds of confusions, paradoxes and suspicions of conspiracy too it seems.

      Georgina,

      Did you read the essay by Phipps? He made aware of a historical fact: The current "Maxwell equation" slightly deviate from original ones by Hertz because they consider a "correction" that was kept for necessary because Michelson (please notice that Michelson, not Morley invented the experiment and performed it already in Potsdam) didn't confirm the existence of a light-carrying aether. Lorentz tried defending the aether hypothesis by means of suggesting length contraction, and this led to Einstein's Special Relativity (SR). There are two main alternatives to SR:

      - Following Lorentz but not Einstein, as did e.g. Selleri and Van Flandern

      - Denying length contraction and Lorentz transformation

      If Phipps is correct then proponents of the latter only need abandoning the mere guess that empty space behaves like a medium. Pentcho is arguing for Newton's idea that particles of light behave like bullets which have mass and are more or less accelerated. Consider this view at odds with the measured data, I tried to explain to Tim Maudlin my reasoning: Newton imagined space like a body. Any body even an empty sheet of paper is something with boundaries one can refer to. Leibniz considered space as a (perhaps infinite) amount of mutual relations. This does not imply a naturally preferred point to refer to; it is more appealing to me. I wonder if Tim will be in position to object.

      In this sense, I consider me a relativist but not a Relativist.

      To me, objective reality is something conjectured to be logically and experimentally self-consistent in the sense that there is only one reality. Although my conjecture may differ from the attribution of others, we will nonetheless agree on that there is only one objective reality. Hopefully this does not sound agnostic. I am confident being more often correct than wrong.

      Eckard

      Eckard, I had not read it but have now.

      I'm happy for substantial objects that are rigid to be invariable with translation at constant speed and for the parts of an image of the same object to be co variant as an observer moves such that different sensory data is input from which the observed output manifestation of the object will be formed. They are not incompatible if it is accepted that what is seen is not the substantial object itself but a representation fabricated from sensory data. At everyday speeds of constant motion neither rigid objects nor their images are distorted and so both kinds of relativity give similar results.

      Re a singular objective reality:I think Johnathan Dickau's example of measuring coastlines gives a good indication that there is not necessarily one objective reality. (Objective reality could be called multi or inter subjective reality.) A result can be agreed by many observers or many by repeats of an experiment yet the result is only true in the context of the experimental protocol used. Repetition does not make it the absolute truth, that disallows other true but seemingly contradictory outcomes. The measurement of the coastline depends upon the scale used to carry out the measurement. The smaller the scale the longer the coast line is found to be. The Object reality IE. what the substantial object (being considered) itself is (without measurement), is the absolute truth and source of all of the differing but valid objective measurements.

      Georgina, Eckard et al...

      Georgina, when you say, "Galilean invariance /Newtonian relativity is about substantial objects existing in absolute space... etc", it seems to me confusing to say 'absolute space and uni-temporal time' and at the same time 'infinitely many universal sized reference frames'. In the Newtonian picture there is only one Absolute space and time, not many but there are other reference frames within that Absolute reference frame. For illustration, there can be people walking at different paces in different directions inside a ship like the Titanic, oblivious of the speed that ship is travelling. However, this is a local frame and would appear differently in a higher order reference frame of the Earth. Which in turn would appear differently from the Solar system observation frame, which in turn would be different from the Galactic, etc till the highest order in the hierarchy the Absolute frame is reached. Which is why, when one says he is moving at a particular speed, it is necessary to say with respect to what.

      re: Galilean invariance /Newtonian relativity is about substantial objects VS Einstein's relativity is dealing with manifestations produced from data carried by light.

      One should be careful here not to confuse an objective reality with an illusion. If I get you correctly, in your preferred terminology, Object reality should not be confused with Image reality.

      I seem however to disagree with your statement that, "Both are necessary in a complete description of the entirety of reality. It is not that only one is correct and the other is false. Confusing the two types of reality causes all kinds of confusions, paradoxes and suspicions of conspiracy too it seems."

      Physics should be described by Objective reality not by illusion, while seeking to explain the source of the illusion using objective physics only. It is when trying to do physics with illusion or image reality that paradoxes surface. To illustrate, it is an illusion/ image reality that we on Earth are stationary and not moving in space, but rather other spatial objects like the Sun and Moon are doing the moving. It is however an objective reality that we are actually in a spacecraft cruising at an unbelievable 30,000m/s about the Sun. It is the duty of physics to explain how the illusion of being motionless is conveyed or came to be, when in actual fact we are cruising at high speed. To therefore say, "It is not that only one is correct and the other is false", will seem wrong in that sense. We cannot be motionless and moving at the same time. One is correct, the other is false but its falsity needs to be explained with physical principles, just the way Galileo and Newton have done for us.

      Eckard,

      That essay by Phipps is the work of an old master, very good at his game. We need more of such people in physics. I see he has other papers in the Galilean relativity journal, but available only by subscription. There is a similar essay by Neal Graneau but not comparable to that of the 90 year old master IMO.

      Eckard, I know your preferred model but you have done a very good job exposing clearly the issues in contention.

      Now,

      IF length contraction and Lorentz transformation is denied, and

      IF Phipps is correct

      You suggest abandoning the idea that empty space behaves like a medium, but

      IF empty space behaves like a medium

      Is it impossible that there is invisible matter that can act like a light carrying medium and be gravitationally bound to and accompany the earth in its celestial motion? Is there evidence that this type of matter exists abundantly? From Newtonian principles, orbiting bodies obey F = GMm/r2 = mv2/r

      So, GM/r = v2. It follows that at a given radius, r knowing v, we can calculate M. If we do this calculation from a high value of v at an orbital distance, r, and obtain a high M, but looking around with telescope calculate the masses of all the dust particles, asteroids, planets, luminous matter and add all this up and get less than 10% of the required M, what next? If we are not to throw away the Newtonian principles that have taken us to the moon and back, and that have been guiding our satellites in orbit, then we must accept/ consider the idea that not all the matter present is in visible form thus preserving the Newtonian relationship of v to r. Come to think of it, why must all matter be visible and made of atoms? Are we the manufacturers of matter? So, going by the Sun's high galactic orbital velocity, v at a radius, r from the centre of the the Milky Way, and the observed amount of luminous matter internal to that radius, it seems that the three IF's above can still be satisfied without "abandoning the mere guess that empty space behaves like a medium", if we consider the possibility that this invisible matter was an active but unseen participant in the experiments of Michelson in Potsdam and other subsequent ones. Which participation made it impossible for light velocity to be influenced at earth surface by earth motion during the experiments, while for a fact earth motion affects light velocity of more distant sources traversing space and matter that is not gravitationally bound to earth surface.

      Regards,

      Akinbo