View source for Relativity: a Pillar of Modern Physics or a Stumbling Block

{{Infobox paper
| title = Relativity: a Pillar of Modern Physics or a Stumbling Block
| url = [http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6833.pdf Link to paper]
| author = [[Gurcharn S Sandhu]]
| keywords = [[Relativity]], [[Reference frame]], [[Absolute motion]], [[Spacetime]], [[Mass-energy equivalence.]]
| published = 2011
| volume = Proc. of SPIE Vol. 8121
| number = 812109
| num_pages = 15
}}

'''Read the full paper''' [http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6833.pdf here]

==Abstract==

Currently, the theory of Relativity is being regarded as one of the main pillars of Modern Physics, essentially due to its perceived role in high energy physics, particle accelerators, relativistic quantum mechanics, and cosmology. Since the founding assumptions or postulates of Relativity and some of the resulting consequences confound the logic and common sense, a growing number of scientists are now questioning the validity of Relativity. The advent of Relativity has also ruled out the existence of the 19th century notion of ether medium or physical space as the container of physical reality. Thereby, the Newtonian notions of absolute motion, absolute time, and absolute reference frame have been replaced with the Einsteinian notions of relative motion, relative time, and inertial reference frames in relative motion. This relativity dominated viewpoint has effectively abandoned any critical study or advanced research in the detailed properties and processes of physical space for advancement of Fundamental Physics. In this paper both special theory of relativity and general relativity have been critically examined for their current relevance and future potential. We find that even though Relativity appears to be a major stumbling block in the progress of Modern Physics, the issue needs to be finally settled by a viable experiment [Phys. Essays 23, 442 (2010)] that can detect absolute motion and establish a universal reference frame.

==Overview==

Published in the SPIE volume ''The Nature of Light: What are Photons? IV'' (2011), this paper is a systematic case that [[relativity]] should be dismantled and replaced, and — unusually for such a case — that the question is settlable by a specific table-top-scale experiment the author has costed out. Sandhu's charge is not primarily that relativity gives wrong numbers but that it has "inadvertently blocked further research in space physics": by abolishing a preferred frame it has removed any motive for investigating the detailed properties of physical space, which he regards as the real container of physical reality.

The paper's organising distinction is between ''coordinate space'' and ''physical space''. Coordinate space, with its unit scales and metric, is "our human creation intended to facilitate the quantification of relative positions"; physical space is the actual spatial extension of the universe in which particles and fields are embedded. Sandhu's key claim is that metric scaling belongs exclusively to coordinate space, whereas permittivity, permeability and intrinsic impedance belong exclusively to physical space — and that relativity, in both its special and general forms, is built on a systematic confusion of the two. From this he argues that special relativity's postulates are logically flawed, that spacetime in general relativity is a computational template rather than a physical entity, and that the practical successes usually credited to relativity in fact belong to a separable principle of mass–energy equivalence.

==The argument==

===Mass–energy equivalence as a stand-alone concept===

Sandhu first tries to detach ''E'' = ''mc''<sup>2</sup> from special relativity. He notes that the concept predates Einstein: Nikolay Umov alluded to the inertial property of energy as d''E''/d''m'' = ''c''<sup>2</sup> in 1873 in ether-based studies; [[Henri Poincaré]] in 1900 deduced that electromagnetic field energy behaves like a fictitious fluid of mass density ''E''/''c''<sup>2</sup>; and Olinto De Pretto's 62-page paper of 29 November 1903, ''Hypothesis of Aether in the Life of the Universe'', used ''mv''<sup>2</sup> for the energy stored in matter with ''v'' identified as the speed of light. All these routes, he stresses, went through electromagnetic waves or the ether — "when originally introduced in the framework of ether, [it] did not require the framework of SR."

He then derives the velocity dependence of [[mass]] from the inertial property of energy alone, taking d''m'' = d''E''/''c''<sup>2</sup> as the sole premise. With d''E'' = ''F''·d''s'' and ''F'' = d(''mv'')/d''t'', substitution gives d''E'' = ''mv'' d''v'' + ''v''<sup>2</sup> d''m'', hence d''m'' = (''mv''/''c''<sup>2</sup>)d''v'' + (''v''<sup>2</sup>/''c''<sup>2</sup>)d''m''. Writing ''x'' = ''v''/''c'' this becomes d''m''/''m'' = ''x'' d''x''/(1 − ''x''<sup>2</sup>), which integrates to ''m'' = ''m''<sub>0</sub>/√(1 − ''v''<sup>2</sup>/''c''<sup>2</sup>) — the standard relativistic mass relation, obtained without any of the postulates of special relativity. A parallel integration recovers the kinetic energy as (''m'' − ''m''<sub>0</sub>)''c''<sup>2</sup>. Sandhu concludes that high-energy physics, particle accelerators and relativistic quantum mechanics can all be sustained on mass–energy equivalence alone, leaving only cosmology genuinely dependent on relativity proper.

===Reference frames and the first postulate===

Sandhu argues that a centre-of-mass frame for any closed volume of ''N'' particles is a genuinely preferred frame: in it the total momentum is zero and the total mass–energy content is minimum. He points to the real astronomical practice of the International Celestial Reference System, whose Barycentric and Geocentric Celestial Reference Frames are anchored at the barycentre of the solar system and the geocentre respectively, as evidence that physics in fact uses such frames and does not use a family of frames in relative motion. "It would be quite illogical and misleading if the IERS is asked to create many more celestial reference frames in relative uniform motion with respect to the BCRF."

He presses four points: that it is particles which move, not frames; that a separate frame per particle defeats the purpose of a frame; that no inertial frame in uniform motion relative to the barycentric frame can actually be ''established'', since no material body within the solar system moves uniformly, so such frames "can only be defined but cannot be practically established"; and that relative measurements alone are insufficient — for two spacecraft with positions and velocities referred to the barycentre, the dynamics are governed by the individual ''R''<sub>1</sub>, ''R''<sub>2</sub>, ''V''<sub>1</sub>, ''V''<sub>2</sub> and not by the relative quantities ''R''<sub>12</sub> and ''V''<sub>12</sub>.

The formal objection to the first postulate follows: in the barycentric frame the total momentum of the solar system's particles vanishes and their total kinetic energy is minimum; in any frame moving relative to it, neither holds. This difference distinguishes the frames, so the barycentric frame is preferred and "the principle of relativity stands violated." A second objection is philosophical: laws of nature depend on interactions among particles and fields and "cannot be influenced by the arbitrarily defined human artifacts like coordinate systems"; only the ''form'' of their mathematical representation changes, so it is wrong to link the laws themselves to inertial frames at all.

===The second postulate, and contraction and dilation as props===

Since Maxwell's theory gives the vacuum light speed in terms of the permittivity and permeability of physical space, Sandhu argues that ''c'' is a property of physical space and "cannot be derived from the metric properties of coordinate space" — so it cannot be defined with respect to the state of different inertial frames. [[Length Contraction]] and [[Time Dilation]] then appear as "just the props required to support the assumed constancy of the speed of light ''c'' in all IRF in relative motion."

His argument that these are apparent rather than physical rests on two illustrations. A thin spherical glass shell of diameter ''L''<sub>0</sub> at rest in the barycentric frame will be seen contracted along the direction of motion when viewed from a moving frame — but it does not shatter, as it would if its diameter physically contracted; and the same rod is seen with different lengths ''L''<sub>1</sub>, ''L''<sub>2</sub> from frames moving at different speeds. Likewise, a single clock is found to run slow by different amounts by different observers, so the dilation cannot be a physical property of the clock. He traces the whole structure to Einstein's clock synchronisation convention, quoting the 1905 paper: "the latter cannot be defined at all unless we establish by definition that the 'time' required by light to travel from A to B equals the 'time' it requires to travel from B to A." That definition, he says, is arbitrary and was adopted precisely to support the second postulate.

===Spacetime is not a physical entity===

The general-relativity section carries the paper's most technical argument. Sandhu treats the metric of the undeformed Euclidean space continuum as ''g''<sub>''ij''</sub> and that of a deformed state as ''h''<sub>''ij''</sub>, so that the strain tensor is ''e''<sub>''ij''</sub> = ½(''h''<sub>''ij''</sub> − ''g''<sub>''ij''</sub>). He then invokes the Saint-Venant compatibility conditions from continuum mechanics: for the displacement field integrated from a strain field to be finite, continuous and single-valued, the Riemann tensor formed from the strain components must vanish, which requires both metrics to be Euclidean. But in general relativity the Riemann tensor computed from ''h''<sub>''ij''</sub> is non-zero by construction. Therefore, he argues, the strains implied by the Riemannian metric fail the compatibility conditions and would produce physically invalid discontinuities in the space continuum — so the four-dimensional spacetime manifold cannot be a physical entity. He adds a terminological complaint: general relativity "assigned a misleading term 'curved space' for a non-zero value of the Riemann tensor in Riemannian space, when it actually implies 'deformed space'."

A second, independent argument is causal. He contrasts the ''presentist'' view, on which physical entities exist only at the present moment and the next state evolves from the present by the operation of physical law, with the ''eternalist'' block-universe view implied by treating spacetime as real, on which the state at all future instants already exists. Using the illustration of a thin metal sheet in the XY plane of an XYT manifold, he argues that a predetermined future state "does not permit a causal evolution of the physical state" and so violates cause and effect, which is the basis of all scientific study.

The third argument concerns metrics as graphical devices. Sandhu shows that the curve ''y'' = ''ax''<sup>b</sup>, a curve on a uniform-scale plot, becomes a straight line on log–log axes, with metric coefficients exp(2''X'') and exp(2''Y'') in the substituted coordinates — so a change of differential scale changes the apparent shape of a curve without touching the physics. He notes that a particle in a circular orbit traces a helix in XY–T space, and that "the helical trace does not physically exist anywhere at any time; it is just a mathematical or graphical representation of the motion of a particle over a period of time." Distance–time space is not naturally metrized, since distance and time scales can be fixed independently and no invariance of the arc element is imposed. Minkowski's constraint (d''S'')<sup>2</sup> = ''g''<sub>''tt''</sub>(''c''d''t'')<sup>2</sup> − {''g''<sub>''xx''</sub>(d''x'')<sup>2</sup> + …} ''introduces'' such an interlinking by hand, and has the effect of imposing ''c'' as an upper speed limit on geodesics.

From this Sandhu offers his positive reading of general relativity: the pseudo-Riemannian manifold is "an abstract mathematical differential scale template manifold", whose metric coefficients are correlated with mass–energy density through the field equations so that Newtonian trajectories come out as geodesics. He grants that limiting the propagation of gravitational influence to ''c'' "may be regarded as an improvement over the Newtonian gravitation" — but insists the correlation established through the field equations "is essentially an empirical correlation", validated only by its success in simulating trajectories.

===The proposed experiment===

The paper closes with a concrete test, developed from his 2010 ''[[Physics Essays]]'' proposal. Define a Universal Celestial Reference Frame at rest with respect to the centre of mass of the universe and non-rotating with respect to the celestial background; motion relative to it is absolute motion. Two stations A and B separated by distance ''D'' and moving with common velocity ''U'' along AB satisfy ''D'' + ''U''·''T''<sub>u</sub> = ''c''·''T''<sub>u</sub> for the up-link and ''D'' − ''U''·''T''<sub>d</sub> = ''c''·''T''<sub>d</sub> for the down-link, so eliminating ''D'' gives

: ''U''/''c'' = (''T''<sub>u</sub> − ''T''<sub>d</sub>) / (''T''<sub>u</sub> + ''T''<sub>d</sub>).

The absolute speed follows from one-way timings alone; the separation need never be measured. The proposed hardware is two microwave towers or tall buildings about 30 km apart with equipment at about 20 m height: a diode-pumped solid-state pulsed laser at 1064 nm with about 1 mJ per pulse and 1 ns pulse width; a detector array of Geiger-mode avalanche photodiodes; a caesium atomic clock with a rubidium oscillator at each end, synchronised side by side before separation; a high-precision event timer; and a data acquisition computer. Pulses are fired alternately at about one-second intervals over 48 hours in an east–west orientation, then repeated north–south, and the diurnal sinusoidal variation of (''T''<sub>u</sub> − ''T''<sub>d</sub>) is extracted. Sandhu states the prediction sharply: under special relativity |''T''<sub>u</sub> − ''T''<sub>d</sub>| must be of order zero, whereas if the second postulate fails it should peak at roughly 100–200 ns. "All items of the test equipment are available off the shelf and the experiment is doable by university students/researchers."

==Assessment==

The paper's real strength is its final section. Much anti-relativity writing ends in assertion; Sandhu ends in a wiring diagram, a parts list, a 48-hour data-taking protocol, a numerical prediction and a stated null expectation from the theory he is attacking. That is the right shape for a dissenting argument, and the insistence that the matter "needs to be finally settled by a viable experiment" is more scientifically serious than most of what surrounds it. The coordinate-space/physical-space distinction is also a genuine and under-discussed point: the observation that a helical worldline "does not physically exist anywhere at any time" is a fair corrective to loose talk about the fabric of spacetime, and the log–log demonstration that a change of metric changes an apparent shape is elementary but well made. His historical section on Umov, Poincaré and De Pretto is accurate and worth having, and the derivation of ''m'' = ''m''<sub>0</sub>/√(1 − ''v''<sup>2</sup>/''c''<sup>2</sup>) from d''m'' = d''E''/''c''<sup>2</sup> alone is a clean piece of work.

But that last derivation cuts against the paper's thesis rather than for it. It assumes d''E'' = ''F''·d''s'' with ''F'' = d(''mv'')/d''t'' in a single frame and takes ''c'' as a universal constant in the relation between energy and inertia; what it shows is that relativistic dynamics can be reached from a different starting point, not that the postulates are false. Every experimental success he attributes to "mass–energy equivalence, without SR" — accelerator kinematics, muon lifetimes, particle decay — uses the same Lorentz factor, and none is thereby freed from the transformation properties that generate it.

The frame arguments contain a definite error. It is true that momentum vanishes and kinetic energy is minimal in the centre-of-mass frame, but that is a property of the ''system'', not of the laws; special relativity's first postulate asserts that the ''laws'' take the same form in all inertial frames, which is untouched by the fact that a particular system has a distinguished frame. Every isolated system in Newtonian mechanics has the same distinguished frame, and no one takes that as refuting Galilean relativity. The claim that inertial frames "cannot be practically established" because no body in the solar system moves uniformly proves too much: on that standard the barycentric frame is not established either, since the solar system is accelerating in the Galaxy. The glass-shell argument likewise misreads the theory — length contraction is not a stress applied to an object, but a statement about the simultaneity convention used to locate its ends, so no theory predicts the shell should break.

Most importantly, the paper omits the evidence that would decide against it. It states that time dilation "is not physical but an apparent effect", but does not address the measurements that make dilation a matter of accumulated proper time rather than appearance: the Hafele–Keating flying-clock experiment, the roughly thirtyfold extension of muon lifetimes in storage rings, and the daily operational corrections in GPS. Nor does it engage the modern one-way and two-way isotropy tests — Michelson–Morley-type experiments with cryogenic optical resonators now bound anisotropy in ''c'' at the level of parts in 10<sup>18</sup>, many orders below the 100–200 ns effect predicted here for a 30 km baseline. The compatibility-conditions argument against curved spacetime assumes what it sets out to prove: Saint-Venant's conditions govern the strain of a material continuum embedded in a flat background, and applying them to spacetime presupposes that spacetime is such a continuum with a flat embedding. And the paper does not mention the classical tests — perihelion precession, light deflection, Shapiro delay, gravitational redshift, binary pulsar decay — which its "template manifold" reading must still account for, since the "empirical correlation" it dismisses is precisely what makes those predictions quantitative rather than fitted.

The presentist argument against the block universe is a real philosophical position, not a physical refutation; the field equations are local and hyperbolic and evolve data forward from a spacelike surface, which is causal evolution in exactly the sense Sandhu demands. Recognising the block interpretation as an interpretation, rather than a consequence, would strengthen his case rather than weaken it.

The proposed experiment, though, remains the paper's best contribution and it deserves to be evaluated on its merits. Its critical vulnerability is the one Sandhu passes over quickly: the whole measurement depends on the two caesium clocks remaining synchronised after being separated, and the definition of synchronisation for spatially separated clocks is exactly what is at issue between him and Einstein. Any transport or signal-based synchronisation procedure imports a convention, and the sign of the effect he seeks depends on which convention was used. Absent an argument that this circularity can be broken, the test as described measures the convention rather than the motion.

==See also==

* [[Gurcharn S Sandhu]]
* [[Relativity]]
* [[Length Contraction]]
* [[Time Dilation]]
* [[Simultaneity]]
* [[Speed of Light]]
* [[Aether]]
* [[Michelson-Morley Experiment]]
* [[Dayton C Miller]]
* [[Reginald T Cahill]]
* [[Henri Poincaré]]
* [[Physics Essays]]

[[Category:Scientific Paper|relativity pillar modern physics stumbling block]]

[[Category:Relativity|relativity pillar modern physics stumbling block]]

[[Category:Aether|relativity pillar modern physics stumbling block]]

[[Category:Time|relativity pillar modern physics stumbling block]]

[[Category:Philosophy of Science|relativity pillar modern physics stumbling block]]