gr-qc/9807084 30 Jul 1998

GR without SR: A gravitational-domain description of first-order Doppler effects

Eric Baird

Equivalence principles are a major part of modern relativity theory. Gravitational shifts can already be calculated within the time domain as motion shifts, and we examine the consequences of reversing this argument and describing motion shifts outside the time domain, as effects of curvature associated with relative velocity. This unusual "Doppler mass shift" approach appears to resolve some of Einstein's own criticisms of the "SR+GR" model and seems to remove some barriers to the reconciliation of classical and quantum theory. The disadvantage of this model is that constant-velocity problems no longer obey Euclidean geometry. By bypassing special relativity and the special theory's flat-space assumptions, the model also suggests an alternative non-transverse frequency-shift relationship. This difference should be testable.

1. INTRODUCTION

Progress in physics is often made by combining descriptions of seemingly disparate phenomena, and by taking basic equivalence principles well past the point where they might normally be expected to fail. The challenge is therefore to find ideas that are simple but are so "crazy" that they have not yet been properly examined. Einstein's early career provides several examples of "craziness" that worked, from his bold statement that mass and energy really were totally interconvertible, to his presentation of the idea that clocks really did tick more slowly in a stronger gravitational field.

This paper examines the consequences of another "crazy" idea, that our descriptions of gravitational shifts and motion shifts should be completely interchangeable. At first glance, the idea of treating simple propagation shifts outside the time domain as gravitational effects seems absurd - why would anyone want to forgo the safe Euclidean geometry of special relativity and replace it with a model in which spacetime is warped by any form of relative motion between masses? Our answer is that an inherently "curved" model appears to address some of the weaknesses in current classical theory that were outlined by Einstein towards the end of his career, and that the apparent Doppler "mass shift" ("DMS") seen in an approaching or receding object suggests a possible resolution to the black hole information paradox [1]. This paper does not attempt to replace ninety years of fundamental physics based on the special theory, but describes some of the expected features and properties of a single-stage relativistic model based on curvature effects.

In the following text, phrases such as "mass change" refer to the apparent change in inertial and gravitational mass of an object seen by an observer with a particular state of motion and viewing angle. The local rest mass m0 of a particle (number of gravitational field-lines) is unchanged, although the observable field strength is altered at various angles and distances by distortions of the geometry (figure 3).


2. PROBLEMS WITH THE CURRENT SCHEME

There are a number of difficulties associated with the use of SR as a theoretical foundation for more advanced gravitational models, for instance:
  1. Energy and curvature. GR associates localized energy with curvature effects, but SR requires that spacetime be unaffected by arbitrarily-high concentrations of kinetic energy ("[under SR] we must say continuum spatii et temporis est absolutum." Einstein [2], pp. 54-55 ). SR assumes that inertial mass can exist without gravitational mass, but under GR the two are inseparable.

  2. Prior cause. By assuming that spacetime affects without itself being affected, the special theory arguably breaks some basic principles regarding action and interaction ("... it is contrary to the mode of thinking in science to conceive of a thing which acts itself, but which cannot be acted upon.", "Though such a theory is logically possible, it is on the other hand rather unsatisfactory. Newton had been fully aware of this deficiency ...", Einstein [2], pp.54 and 133-134)

  3. Mach's Principle. Although GR was originally designed to conform to Mach's Principle by relating inertia to the presence of background mass (Einstein [2], pp.94-103), the idea is not backwardly-compatible with special relativity, which attempts to describe inertial problems without involving mass-fields [3]. This may explain why Einstein's implementation of a general theory diverged from Mach's Principle [4] and arguably failed to meet its own design criteria by allowing solutions for flat empty space [5].

  4. Absence of dragging effects. SR assumes that the motion of nearby masses has no effect on the local speed of light, even though experimental evidence indicates that signals passed through a moving particulate medium do appear to be dragged by that medium [6]. SR assumes that the gravitational influence of a fundamental point-particle can be ignored, even at negligible distances, where gravitational effects might be expected to be arbitrarily strong.

  5. The extinction theorem. If we aim a wavefront through a particulate medium, and the action of the medium's constituent atoms (acting as signal transponders) is to generate a new wavefront traveling at c with respect to the atoms' shared velocity [7], then we cannot also claim that the motion of a transponder has no influence on the way that its emitted signal propagates.

  6. The "problem of space". Under GR, space is supposed to require a gravitational field in order to have physical existence. ("if we imagine the gravitational field ... to be removed ... there does not remain a space... but absolutely nothing, and also no topological space." [8] "... the concept of space detached from any physical content does not exist" [9] ). Yet the complete absence of gravitational field parameters is a cornerstone of special relativity.

  7. Persistence of motion. With GR, we can say that "space tells matter how to move, matter tells space how to bend". Ideally, a model would be able to describe all of a particle's motion parameters in terms of the distortion of its fields and/or the distortion of the surrounding region of spacetime, since this would allow motion to be "frozen into" a snapshot of a moving object, bypassing Zeno's third paradox [10] without involving infinitesimals. This principle for the persistence of motion does not exist within the undistorted (or uniformly-contracted) space of special relativity [11].

  8. Measurement-dependence. In a fully "curved" spacetime model, the state of motion of a sensor will physically affect the geometry of the surrounding region in a manner reminiscent of quantum mechanics ("No information-extraction without geometry change"). This idea does not really have a counterpart under strict special relativity.

  9. The black hole "information paradox". QM and GR disagree as to whether black holes emit indirect radiation like an Eighteenth Century "dark star" (Hawking radiation, see: Thorne [12], pp.122-123, 133, 252-253, 412-448 and Baird [13] [14]) or are completely black (Wheeler's "black hole", MTW [15] chapter 33 pp.872-875). This discrepancy has implications for SR, which established the relationships that led to the "black" GR description. Einstein reputedly never accepted this aspect of his general theory [16] and treated its more extreme predictions with some scepticism ("But why should anybody be interested in getting exact solutions of such an ephemeral set of equations?" [17] ). While Einstein seems to have been troubled by perceived philosophical inconsistencies in his own relativistic models, and described the two-stage "SR+GR" approach as a historical accident that could no longer be objectively justified ("I do not see any reason to assume that the heuristic significance of the principle of general relativity is restricted to gravitation and that the rest of physics can be dealt with separately on the basis of special relativity, with the hope that later on the whole may be fitted consistently into a general relativistic scheme." [9], his own efforts using advanced mathematical techniques to derive a single unified replacement theory that bypassed special relativity (a "GR without SR") were unpopular ("they think that I am crazy on this subject" [18] ) and ultimately unsuccessful.

We shall now add one further awkwardness to our list:

  1. Inconsistent use of "observables". Although SR is supposed to be a theory of observed reality ("what you see is what you get"), this principle is suspended if any part of the data can be explained away as a first-order Doppler effect. In these cases, SR allows the observer to treat the raw data differently according to their beliefs about distant signal propagation [19].

Our chosen method of attack is to concentrate on this last problem. The calculation of gravitational shifts from motion-shift principles is already a basic part of general relativity [20], but the obvious corollary (calculation of motion shifts as gravitational shifts) appears to be more troublesome. Although Einstein's 1905 electrodynamics paper [21] and his 1920 Leyden lecture [22] appear to reject the idea of "[assigning] a velocity vector to a point of the empty space in which electromagnetic processes take place", by 1930 Einstein was embracing the idea ("of attributing direction as well as metrical structure to space" [18] ) as the basis of a unified theory. Our investigation incorporates motion vectors into the metric by taking the existing gravitational well that must surround an object with mass and adding a "tilt" according to the object's velocity relative to background matter. This idea of velocity-dependent curvature threatens the validity of the flat-space derivations used to construct the special theory of relativity, and which allow the SR equations to be treated as a unique mathematical solution.


3. PHENOMENOLOGY

There are several reasons to suspect that motion shifts can be calculated within a Dt=0 snapshot as gravitational-domain effects:

3.1. Observed timeflow

Simple differential timelag arguments tell us that approaching objects appear to age faster and receding objects appear to age more slowly (simple Doppler shift). A gas-filled container will appear to have a greater rate of activity when it is approaching than when it is receding, the gas molecules will appear to have a higher speed (lowered inertial mass) within the container, and the container will seem to emit radiation faster, with a correspondingly smaller wavelength and higher energy.

If we judge "apparent mass" by watching the object's reaction to a test force calibrated in its own frame, or to a force applied by the observer, then this property has a higher value when an object recedes and a lower one when the object approaches [23].

3.2. Observed ruler-changes.

Special relativity associates an apparent mass-increase with a corresponding length-reduction, so if we take the DMS idea seriously, we should expect an approaching (blueshifted) object to appear to have increased length. This sort of observed behavior is already part of current physics - approaching objects do appear lengthened and receding objects contracted, [24] with the degree of length-change matching the frequency-change in the object's emitted signals [25] [26]. Photographed lengths do appear to alter just as we would expect if we interpreted non-transverse Doppler shifts as mass-change effects.

3.3. Aberration as the result of bipolar gravitational lensing

If we treat the region ahead of a moving point-object as being mass-reduced and the region behind the object as mass-dilated, then by applying Huyghens' principle, we arrive at a map of the region that involves outgoing light-rays leaving the point-object having a net rearward deflection, towards the region of slowest observed timeflow [20] [27] [28]. This would seem to be the DMS "gravitational" description of aberration effects when the speed of light is taken to be constant relative to the background frame.
aberration of outgoing lightrays
Figure 1 (a): velocity aberration, (b): lensing aberration, (c): gravitational aberration
However, if the object subtends a significant angle with a single observer (if the object is large enough or close enough to fill a significant part of the observer's field of view), the shift pattern reverses, with the (receding) nose of the object appearing redshifted and the (approaching) rear appearing blueshifted. Applying DMS and Huyghens' principle now results in a prediction of forward-swept lightbeams, which is the expected pattern if c is instead constant in the emitter's frame.

Taken together, these two descriptions appear to describe lightspeed constancy as a proximity effect, with light "thrown" forward close to the moving emitter, but taking up a speed of c relative to the background as it leaves the emitter's influence (see section 4.1).

Frame-invariance is discussed in section 4.2.

3.4. Gravitational lensing as a consequence of aberration

The argument in section 3.3 can also be reversed. If an outside observer sees a moving object's geometry to be distorted, then all of the object's geometrical properties must appear to be redistributed in exactly the same way for the object to be unaware of its own (supposed) distortion. Once we apply this angular redistribution to the object's gravitational field, we again arrive at a description of an object whose gravitational influence is intensified toward the redshifted side (concentrated angular density) and weakened toward the blueshifted side (diluted angular density). This description seems to be the inverse of Huyghens' argument.

If the object's "mass" is wholly a function of its fields, and these fields are redistributed by relative motion, then we would also expect this field redistribution to produce a gravitational frequency-shift. The strength of this shift effect (in the forward and rearward directions) appears to match the frequency-shift law associated with whichever propagation is model being used. Rather than predicting that a moving object appears doubly Doppler shifted, DMS says that the "gravitational" shift calculated from aberration arguments actually is the motion-shift, described within the gravitational domain instead of the time domain.


4. INVARIANCE

4.1. Local lightspeed constancy

If two objects with relative velocity v are separated by an effective gravitational gradient with an associated terminal velocity v, then light passed between the objects and riding this gravitational gradient can be emitted at c relative to the emitter and received at c relative to the absorber, and can have a range of intermediate velocities in the intervening region that are dictated by the local gravitational properties encountered along its path. This provides a gravitational mechanism for local lightspeed constancy that is essentially Einstein's amended 1911 description ("The principle of the constancy of the velocity of light holds good according to this theory in a different form from that which usually underlies the ordinary theory of relativity." [20] ), when motion shifts are considered as gravitational effects
(NB: in this model, the equivalent gravitational terminal velocity between two events is route-dependent rather than absolute).

If we attempted to measure an intermediate speed in this region by introducing a physical probe with a new velocity, the presence of the probe would alter the surrounding geometry so that we would again get a local measurement of c relative to the probe. DMS models include a feature of quantum mechanics in that the act of measurement cannot be isolated from the system that is being examined.

4.2. Recreating frame invariance and Newton's Third Law

Considered separately, the ideas of DMS and "aberrated gravitation" both generate apparently insuperable problems:
  1. DMS and gravitational braking. If DMS predicts that a moving object sees rearward environmental matter to be mass-dilated and forward environmental matter to be mass-reduced, then we might expect the object to experience a rearward gravitational attraction that would slow its motion through its environment with respect to a local preferred frame.

  2. Aberration and gravitational acceleration. If conventional aberration makes a moving object "see" more environmental matter to be in front of it than behind it (see published maps [29] ), then we might expect the object to experience a forward gravitational attraction towards the region where matter appears to be most concentrated, further increasing the object's speed relative to its environment. Such a universe would be deeply unstable.
Taken individually, either result would normally be bad enough to kill a theory outright. However, since we are invoking both effects, it is conceivable that these two "problems" cancel, allowing us to derive Newtonian frame-invariance instead of taking it as a starting point. In fact, we need something very like DMS to counter the second effect in conventional theory, if an object's "optically observed" and "gravitationally observed" positions are to point to the same position. If we avoided invoking a DMS-type mechanism by saying that these two sets of observed positions do not coincide, then we would have a whole new series of paradoxes and redefinitions to deal with - we would no longer have a clear definition of "observed position", and would have to consider whether a divergence of both "observed" positions would give us an illegal measure of an object's absolute speed.

Proof of complete cancellation is more difficult and might depend on the choice of shift equations, so for now we shall restrict ourselves to noting that the two effects that might be expected to destroy frame invariance (forward acceleration and rearward acceleration) act against one another in a homogenous universe [30] (although a moving object can still lose momentum to nearby passing particles by dragging and gravitational braking in an inhomogenous universe [31] ).


5. CHOICE OF SHIFT EQUATION

5.1. Shift formulae

Special relativity satisfies the principle of relativity by allowing each observer to decide that spacetime is "flat" and stationary with respect to themself. The principle of relativity appears in a different form with DMS, which allows all physical observers to agree that relative motion between onbjects distorts spacetime and affects mutual observations (e.g. angle-aberration).

The distinction between "flat" and "curved" models is a critical one, as it dictates our choice of non-transverse shift equation. If we take the three usual non-transverse Doppler equations [32],
f'/f=(c-v)/c
. . . (1)
f'/f=[(c-v)/(c+v)]^0.5
. . . (2)
f'/f=c/(c+v)
. . . (3)
we find that the assumption of a particular flat reference-frame leads to a combination of (1) and (3), a situation that SR then "relativises" by using the root product of both equations, (2). SR's chosen shift formula is related to (1) and (3) by the ubiquitous Lorentz term.

Once we lose the assumption of flat space, we no longer have to include both (1) and (3) in the description - we might instead choose to try to apply just (1) throughout. This first equation does look promising as the basis of a relativistic model and can be used to generate many of the usual "relativistic" results, including the E=mc² relationship [33], Einstein's 1905 aberration formula [34], and the usual r=2M Schwarzchild event horizon radius. However, (1) is generally supposed to be inferior because of its basic incompatibility with models based on the idea of flat space [35].

5.2. Comparison

If we take the case of an object moving at extremely high speed and viewed by "stationary" observers placed before and behind, we find that equation (1) allows for the existence of hidden variables. Under special relativity, when the rearward shift tends towards f'/f=0, the forward blueshift tends towards infinity, and both sets of observations break down at the same "illegal" velocity (v=c). With shift equation (1), though, this infinite rearward redshift happens when the forward blueshift is still only f'/f=2, so even though an object appears clock-stopped to the rearward observer, a colleague placed ahead of the object can continue to see a legal (doubled) rate of timeflow in the object. It is then also legal for this forward observer to see the object firing its engines and accelerating to f'/f>2, while the additional velocity-increase (and subsequent events) are hidden from the rearward observer by a recession event horizon [13].

Similarly, we find that (1) predicts that an object trying to hover at the r=2M surface of a superdense object only sees the outside universe to have a doubled frequency rather than an infinite rate of timeflow, so that escape can be attempted in finite time (as with indirect "dark star" radiation) [13]. In such a model, we can follow Einstein's comments to Heisenberg about quantum mechanics and say that it is no longer the "observables" that define the theory, but rather, that "it is the theory which decides what can be observed." [36].

5.3. Energy conservation

A casual objection to the use of (1) might be that it appears to break energy-conservation laws - if matter or energy passes in and out of a gravitational well with terminal velocity v [37], equation (2) appears to predict no round-trip gain or loss in energy because the equation is inverted by a change in velocity sign, whereas (1) predicts a final energy-loss of 2gh/c². In fact, SR can be used to predict the same result [13], and strict energy-conservation is not necessary for round-trip shifts - energy increase is forbidden, but a mass repeatedly traveling up and down across a gravitational gradient can lose energy by emitting gravitational waves. Similarly, if the energy of a photon passing through a gravitational well temporarily dilates the well, this should produce a (small) gravitational wave, and the emerging photon should therefore have lost a (small) amount of energy. An extreme version of the confined-light argument (in which highly concentrated light produces enough gravitation to become completely self-trapped and acquires a gravitational event horizon to become a "kugelblitz") has already been discussed elsewhere [38].


6. GEOMETRY

6.1. SR and Lorentz contraction

Figure 2 (a) and (b) show the internal wavelength-distances behind a spreading wavefront emitted by a "moving" object, derived from shift equations (2) and (1) and the principle of relativity [34].

Figure 2(a) shows the internal wavelength-distances according to Einstein's 1905 electrodynamics paper. This ellipsoid has constant width and can be turned back into a constant-size sphere by a simple Lorentz-contraction along the motion axis. Although SR would have us believe that the object's wavefront is a sphere with fixed radius as mapped from all frames, we find that if the region inside the wavefront is mapped using wavelength distances, the internal dimensions of the wavefront are increased by the motion of the central object [34].

aberration angles and distances according to equations (2) and (1)
Figure 2: Light-distance ellipses according to (a): SR, and (b): DMS models

Figure 2(b) shows the equivalent wavelength diagram for equation (1). This ellipsoid has a further overall Lorentz magnification, and a constant-width cross-section through each focus. With DMS, we can try to preserve the internal wavelength-distances as geodesics to produce a "tilted gravitational well" around the moving mass that represents the additional curvature components of its kinetic energy. However, with DMS, we also have to remember that the act of filling the region with physical sensors that are stationary in the observer's own frame can affect the behavior of the wavefront, so the act of measurement cannot be isolated from the measurement process.

6.2. DMS and "tilted" gravitational wells

The rough sketches in figure 3 illustrate how these features (for outgoing lightbeams) can be combined geometrically. In figure 3(b), the conventional "gravitational well" embedding diagram 3(a) is altered by "tilting" the well throat to match the tilt of the object's worldline compared to that of surrounding observers. The final diagram includes angular aberrations and wavelength-changes as effects of velocity-dependent curvature.
Putting it all together - the tilted gravitational well
Figure 3 (a): "conventional" and (b): "tilted" gravitational wells

This approach only works if gravitation is a fundamental property of the particle. We cannot easily get to this description by constructing a gravitation-free model of inertia and then "retrofitting" gravitational terms later, since our model does not reduce to SR geometry over small regions in the usual way - here, two bodies with relative motion are always separated by a gravitational gradient, no matter how close they are to one another [39].

This description of tilted geometry and redistributed gravitation can be compared with the diagrams produced by Alcubierre [40] [41], and Will [42]. The Will and Alcubierre pieces discuss the use of (hypothetical, negatively-gravitating) exotic matter to generate a mass-imbalance around an object to produce freefall acceleration, and would also produce (undiscussed) gravitational lensing effects to deflect lightbeams along the acceleration axis and mimic conventional aberration effects. In this example, though, we are applying the description to mundane, everyday phenomena - Alcubierre-style distortions are presented here as an intrinsic property of any system with relatively-moving masses, and as the underlying mechanism that allows frame-invariance and Newton's Third Law to operate.

Again, if we place sensors in the region to confirm its geometry, any relative motion of the sensors will produce additional distortions that will alter the readings taken [43].

6.3. Mass-reduction limits

The usual objection to Alcubierre's description is its use of the idea of matter with negative mass. In a DMS model, there is certainly a forward reduction in an object's effective gravitation, but the level never quite reaches zero and never becomes negative, so the Positive Energy Theorem (which forbids isolated negative masses) does not apply even though we are describing a dipole velocity component for the object's gravitational field. With equation (1), the forward rate of timeflow does not become infinite (apparent zero inertial mass) for any finite velocity.

A very crude form of field-strength reduction also occurs in standard models due to observation timelags - when an object is approaching at a particular distance (in flat spacetime), its observed signals and fields correspond those that were emitted when it was further away than this, so the observed fields for the object at its "true" position are weaker than we would expect if the object was at that same position but stationary. Put simply, a distant object created traveling towards the observer at cSR within a supposedly flat propagation model has no detectable fields, because the object's "new" field-signal (traveling at c) cannot be sensed until the object has already reached the observer's own position. This description becomes more involved in a DMS model.


7. REPRODUCING SPECIAL RELATIVITY

If we accept the previous arguments and equation (1), then if we aim a signal at a "moving" transponder along its motion path and receive the relayed signal at another "stationary" receiver at the object's far side, we will expect a final frequency shift at this receiver of f'/f=(c+v)/c × (c­v)/c), or 1­v²/c².

If we accepted this round-trip "emitter theory" shift result but believed that the region was wholly undistorted by the objects' relative motion, then we could try to argue that since the total signal pathlength is (believed to be) constant, the final redshift must instead be due to additional non-propagation "time dilation" effects, with each frame transition being responsible for an additional non-propagation Lorentz redshift of (1­v²/c²)1/2 on top of any "flat" propagation effects (this flat-space reinterpretation is not perfect [44] ).

By superimposing this correction factor onto the flat-space propagation shift equation (3) we get the SR shift formula (2) - in other words, if we start with the emitter-theory equation and curved spacetime and try to force some of the same key relationships by using round-trip measurements and assuming flat spacetime, we seem to arrive at Einstein's special theory. SR appears to be a flat-space approximation of a curved-space model that uses a different non-transverse shift formula.


8. ASTRONOMICAL ISSUES

Much of the evidence against shift equation (1) is indirect, and relies on signal flight-time arguments that in turn depend on the assumption of flat spacetime. These "non-gravitational" flight-time arguments (which disprove various other models based on (1)) do not hold up against a DMS model.

8.1. Rotating and orbiting masses

GR tells us that that spacetime is completely dragged at the surface of a rotating black hole (e.g. Thorne [12], fig. 7.8, pp. 292). If signals are emitted from vanishingly close to the equatorial surface of a Kerr black hole, the additional offset of the speed of light in the region (tangential to the surface) exactly matches the rotation speed of the hole, so that when the hole is viewed side-on, its receding edge has a stronger pull than its approaching edge, with the difference in nominal lightspeed at these two places exactly matching the difference in recession(/approach) velocity.

The same principle should apply if these two sections of horizon are not connected, but belong to a pair of holes in a mutual circular orbit - a receding hole in a black hole binary should "pull" light more strongly than its approaching twin. Since partial dragging also occurs at a distance from these surfaces where their gravitational influence is weaker, this same partial dragging ought to happen at the idealised surfaces of a conventional double-star system that has a similarly weaker gravitational influence. Although DeSitter [45] [46] and Brecher [47] have both used double-star observations to argue that the speed of light is wholly unaffected by the motion of the emitter, these calculations have been based on the assumption of flat space, and have assumed that any initial lightspeed differences between approaching and receding stars will produce a flight-time offset that multiplies linearly with the distance of the star, over astronomically-large distances. In our revised model, the initial supposed lightspeed difference only really applies to the regions of space where each emitter's own gravitational influence dominates the metric.

As a signal leaves the double-star system, not only does the influence of the emitter on the signal's speed become less significant, but the motion field-effects from both stars become progressively more merged. If the binary system is far enough to treat as a point-source, the root-product superimposition of the "approach" and "recession" field-components gives us an overall gravitational redshifting of the system due to velocity of [(c­v)/c × (c+v)/c]1/2, or just (1­v²/c²)1/2 . In other words, if we treat mass as a field effect and allow field strength to be altered by velocity according to equation (1) the crude superimposition of these two fields gives us the Lorentz relationship used by special relativity.

This argument ignores higher-order effects due to the slight difference in effective pathlength to the two stars. The associated timelags can make the system appear to be unbalanced around its true center of gravity, with the timing-discrepancy being more obvious when the two stars are at different distances to the observer. If the two velocity field-components add differently (due to timelags) at different parts of the orbital cycle, the system can show a periodic imbalance in observed mass (for a single observer). Mapping these observed-mass oscillations by observer-position leads to a map of gravitational waves thrown off by the double-star.

8.2. Spectral lines and atomic velocities within stars

The previous argument only seems to describe partial dragging at the surfaces of most bodies, but this is because we have calculated the surface gravitational effects of r>2M objects without considering that these bodies are particulate. If the atoms making up the star are considered as individual point-particles (or particles with individual radii of r=<2M), then the individual atoms at the star's surface can show complete dragging, even though a simplified model of the star will not.

Another objection to older emitter-theory models was that if individual emitting atoms in the stellar atmosphere showed complete dragging, their thermal motion would give rise to photons being thrown off with different speeds, giving rise to different transit times for Doppler-redshifted and Doppler-blueshifted light from the star. This would then cause a star moving across our field of view to have a rather "streaky" appearance, with a blueshifted leading edge (faster photons) and a redshifted tail (slower photons).

The reported absence of this effect (and the sharpness of spectral lines) has been taken as additional evidence against equation (1). However, the DMS model says that the photon's velocity is only dictated by its emitting atom at extremely small distances, and that a photon leaving a star quickly takes up a speed of c relative the averaged field of the star (the photon leaves the atom at c relative to the atom, but leaves the star at c relative to the star). Again, the motion field-components of the star's atoms merge to produce an overall (thermal) redshift component that relates to the star's internal kinetic energy.

8.3. Dark stars and Hawking radiation

One major consequence of using equation (1) to describe super-dense objects is that we effectively revert to using a form of "dark star" model, with an infalling observer seeing progressively further into the object's gravitational well as they fall, and the apparent event horizon contracting as the hole's proximity and approach velocity increases. With DMS this observed horizon-contraction can be described in terms of an apparent mass-loss in the approaching (blueshifted) star, and direct observations no longer give us a complete data-set - our models also have to take into account the existence of "lurking" variables that are currently only indirectly observable ("virtual" variables), and which can become "legitimate" ("real") after a change in the observer's relative speed, proximity, or acceleration. [48].

Although emissions at r=2M cannot reach a remote stationary observer directly, some models based on equation (1) can allow signals to reach the observer indirectly, by interacting with particles outside the r=2M surface. Until recently, the notion of a super-dense object showing "dark-star"-like behaviour and emitting indirect radiation would have been considered to be quite misguided. However, in the early 1970's Hawking [49], Bekenstein [50] and others produced a quantum mechanical prediction of a similar-sounding form of indirect radiation, although the conflict with GR has led to this effect ("Hawking radiation") being described as a separate quantum effect with no classical counterpart. It may be significant that mis-application of GR to an "obsolete" dark star model can result in a similar description of pair-production outside the horizon [14].

We can now consider the "naive" question, "Does an object traveling at high speed turn into a black hole?". With GR, the answer must be "no", because the acquisition of a gravitational event horizon is associated with a real physical collapse that cannot be "undone" by a later change in the observer's relative velocity (this is one reason why modern physics tends to take "mass" to mean "rest mass"). In a DMS model, the object can appear to gain or lose an event horizon depending on whether the object is receding or approaching, but total collapse does not occur - total collapse is averted in a dark star model by indirect radiation-pressure, which under QM would have to be modeled as the pressure due to Hawking radiation within the r=2M surface. Whether a change of shift equation might really allow the complete equivalence of classical and quantum descriptions remains to be seen, since the initial enthusiasm for the black hole model championed by Wheeler (e.g. MTW [15], ch.33) appears to have discouraged work on alternatives. Although DMS allows a comparatively mundane explanation of Hawking radiation, the high cost of this explanation (replacement of a critical shift equation) means that this explanation is not likely to be well received unless experimental data demonstrates that equation (1) is more accurate than its SR counterpart.


9. EXPERIMENTAL VERIFICATION

Many of the phenomena that we might consider to be evidence for the dragging of light have now been accepted and absorbed into special and/or general relativity - for instance, Fizeau's verification of Fresnel's light-dragging prediction is now used as evidence for the correctness of SR's velocity-addition law [6] [51], and the existence of (very small) binary star signal anomalies, whose absence was originally taken as supporting SR, are now taken as supporting GR descriptions of gravitational waves.

9.1. Direct verification of the non-transverse velocity shift law

While it may seem improbable that we have not yet managed to verify that the SR shift prediction (2) is more accurate that the earlier equation (1), the author has so far been unable to find any direct evidence favoring (2). Since it is often difficult to tell (1) and (2) apart, experimenters tend instead to support (2) by disproving (3), in the belief that (1) has already been disproved by flat-space flight-time arguments such as DeSitter's.

Direct verifications of the supposed superiority of (2) to (1) still seem to be missing from the literature, even though we would expect this difference to have testable consequences.

9.2. Direct verification of the gravity-shift relationship

Pound and Snider have verified the existence of a 2gh/c² round-trip gravity-shift to 1% accuracy in a small earthbound experiment [52], but this round-trip result is common to both (1) and special relativity [13]. The same experiment also measured the one-way shifts, to 6% accuracy. This was still insufficiently accurate to distinguish between (1) and (2).

9.3. Deflection of light-rays by a moving medium

Non-transverse dragging of light by a fluid was verified in the Nineteenth century by Fizeau, and is now taken as evidence in favor of SR's velocity-addition formula (the emitter-theory shift formula can also generate an addition formula) [13].

Transverse dragging by a particulate medium appears to have been verified with spinning transparent disks [53], and circularly polarized light has been shown to exert a torque as it passes through a transparent plate [54].

9.4. Deflection of light by a moving mirrored surface

Dragging by a moving reflective surface seems to be a more difficult subject. A mirror advancing along its own normal is supposed to aberrate reflected rays [51], but it has been reported that mirrors moving along their own plane do not show effects associated with dragging [55] [56].

9.5. Two-stage non-transverse redshift

This experiment has been suggested and discussed in a previous piece [44]. A Lorentz-squared result would seem to favor equation (1) rather than (2).


10. TRANSITION BETWEEN MODELS

There are some headaches to be had in switching from special relativity to this model. Both descriptions agree that an object can never overtake its own light-signals along the same path, and that a stationary set of particle accelerator coils cannot directly accelerate a particle to more than ~300,000 km/s. Both predict observed clock-stopping at recessional lightspeed, and both place an event horizon at r=2M, give the famous E=mc² relationship, and can predict Lorentz time-dilation in a thin ring-mass spun around its axis at v m/s. However, SR treats c as a full constant and redefines v accordingly, whereas under DMS it is perhaps more natural to make c a variable whose value depends on the "gravitational" difference v across the viewing path separating the observer from the region being observed. If we are not dealing with extreme situations (such as black hole problems involving event horizons), the difference in emphasis will often make little or no difference to our calculations.

In other areas the transition is more significant. With DMS, the reconciliation of QM's predictions about black holes with those of classical theory becomes a fairly trivial matter, but the infamous SR "clock paradox" (in which a pair of astronauts accumulate a mutual Lorentz timelag during the constant-velocity parts of their journeys), is even worse with DMS, which predicts a mutual Lorentz-squared timelag. On the other hand, DMS does allow physical acceleration to generate compensating gravitational-wave effects without betraying its geometrical principles.

The consequences for particle physics theory, where the SR equations have long been accepted as an firm base for further theoretical work, are more difficult to evaluate. The task of rewriting modern particle physics around (1) is rather daunting and might not be worthwhile unless experimentation really does show (1) to be superior. Even if experimentation does eventually favor (1), the point that this supposed divergence from SR's formulae has not yet been reported suggests that (2) may still be "close enough" for the difference to be imperceptible in much current engineering work. On the other hand it may be (as happened with the late discovery by chemists of Carbon 60), that useful evidence has already been collected but overlooked.


11. CONCLUSIONS

Special relativity's use of flat spacetime may have been a sensible simplifying assumption in 1905 but seems less appropriate in the late 1990's, and we may now be able to use some of the the lessons learned from general relativity to construct a more sophisticated single-stage theory that does not rely on the validity of Euclidean geometry in moving-body problems. Although it is now more than ninety years since Einstein produced his 1905 electrodynamics paper, and more than forty since he declared SR to be an unsafe foundation for a more general theory of relativity, Einstein's warnings seem to have been largely ignored. Work on a replacement single-stage "GR without SR" has been slow or non-existent since Einstein's death, and given that SR is sometimes presented as being correct "without a shadow of a doubt" [57] ("Only theories consistent with special relativity need be considered." [6] ), and that SR-compliance is widely considered to be a precondition for any credible relativistic description of gravitation (e.g. Will, [58] ), it is perhaps not too surprising that work in this area is unfashionable.

While the "DMS" idea should be of some interest to black hole theorists, it also has a more immediate physical importance in that it suggests that some of SR's predictions may be incorrect, in a situation where conventional theory appears not to have yet been adequately tested. It is the author's opinion that there is a very real risk that future experimental results [44] may conflict with the special theory's non-transverse shift formula (2), and that the physics community should be prepared for this possibility. It may be advisable to carry out some preliminary work on this alternative (overlooked) branch of relativity theory before the experimental results are available.


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EB 1998
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http://xxx.lanl.gov/ G~