Time Dilation

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Wikipedia Dispute: wikipedia:Time dilation

This Natural Philosophy wiki page disputes content found on Wikipedia page wikipedia:Time dilation

Time dilation is the claim, made by Einstein's theories of relativity, that the rate at which time passes is not the same for all observers: that a clock in motion relative to an observer accumulates less time than the observer's own clock, and that a clock deeper in a gravitational potential runs slow compared with one higher up. It is one of the most widely publicised results in modern physics and one of the most persistently disputed on this wiki.

The dispute documented here is rarely about the numbers. Almost every researcher discussed below accepts that moving atomic clocks and fast-moving unstable particles behave differently from clocks and particles at rest, and most accept the Lorentz factor as the correct quantitative description of that difference. What they dispute is the interpretation: whether time itself dilates, or whether physical clocks are simply retarded by their motion through a medium or their position in a field; whether the effect is symmetric between two observers, as the relativity principle demands, or asymmetric and absolute, as the experiments appear to show; and whether the experiments routinely cited as confirmation actually test what they are said to test. The archive collected on this wiki contains some fifty papers on the subject, running from 1959 to the present.

Closely related articles on this wiki treat the paradox in detail — see Twin paradox — and the wider theoretical setting, see Special relativity and Relativity.

The mainstream account

Einstein's 1905 paper "On the Electrodynamics of Moving Bodies" derived, from the relativity principle and the postulated constancy of the speed of light, the relation

connecting the time <math>T_o</math> elapsed on a clock at rest in one inertial frame with the time <math>T</math> assigned to it in a frame moving at relative velocity <math>v</math>. Because the expression depends only on the relative velocity, and because that relative velocity is the same for either observer, the effect as derived is reciprocal: each of two observers in uniform relative motion finds the other's clock to be running slow. The associated result, the relativity of simultaneity, means the two observers also disagree about which distant events happen at the same moment; see Simultaneity.

In the same 1905 paper Einstein went further and asserted that if two clocks initially together are separated, one making a round trip and returning, the travelled clock will have accumulated less time than the one that stayed behind. This introduces an asymmetry that the symmetric derivation does not obviously supply, and it produced the long controversy known as the clock paradox, renamed the twin paradox after Langevin's 1911 popular presentation. The mainstream resolution assigns the asymmetry to the travelling clock's change of inertial frame — its acceleration or turnaround — and treats the reciprocity of the uniform-motion phases as unproblematic. That argument is treated at length in Twin paradox.

General relativity adds a second, distinct effect: gravitational time dilation, in which a clock lower in a gravitational potential runs slow relative to one higher up. The two effects have opposite signs for an orbiting satellite, whose velocity slows it and whose altitude speeds it up.

The standard experimental case rests on four families of result. First, the extended lifetimes of fast unstable particles — muons produced by cosmic rays in the upper atmosphere reaching the ground in numbers far larger than their 2.2 µs rest lifetime would allow, and mesons circulated in accelerator storage rings. Second, the Mössbauer-effect experiments of Pound and Rebka and of Hay, Schiffer, Cranshaw and Egelstaff, which measured frequency shifts due to thermal motion and to rotation. Third, the 1971 Hafele–Keating experiment, in which caesium clocks were flown east and west around the world and compared with clocks left at the U.S. Naval Observatory. Fourth, the operation of the satellite navigation systems, whose clock corrections are computed from both the velocity and the gravitational terms; see GPS.

On the received account these results, taken together, establish that time dilation is a real physical effect and not merely a way of speaking. Everything that follows is the case made on this wiki that this conclusion is either unproven, incorrectly interpreted, or replaceable by a physical mechanism that requires no dilation of time at all.

Reciprocity: symmetric appearance or asymmetric fact?

The oldest and most frequently repeated objection here is that the two things special relativity is said to establish cannot both be true at once. If clock A runs slow relative to clock B and clock B runs slow relative to clock A, the effect cannot describe an accumulation of proper time; and if the effect does not describe an accumulation of proper time, it cannot by itself account for one clock returning younger than the other.

Nick Percival states the objection directly in Data That Allegedly Proves Special Relativity Disproves It (2013), which analyses the GPS, Hafele–Keating and muon-decay data and argues that they do not support special relativity's time dilation and in places count against it. In Analyzing Special Relativity's Time Dilation Within The Context of Lorentz Relativity (2016) he sets out the alternative he prefers: Lorentz relativity, in which clock retardation is a function of absolute velocity with respect to a single preferred frame, is a valid theory; special relativity, he argues, altered it by adding the constant-velocity-of-light principle and the claim that every inertial frame reproduces the properties of that one preferred frame.

Raymond H Gallucci argues in Time Dilation in Relativity (2013, also published as "Time Dilation in Relativity") that the effect is apparent only — that when one frame moves relative to another at constant speed, it merely appears that its clock runs slow. He makes the case with a worked box-and-flashes construction in which simultaneous flashes at the two ends of a box are used to fix the "true" length for comparison.

Allen D Allen examined the same problem in "Time Dilation and the Spatial Interval for which dx/dt is Speed" (1988), starting from the requirement that the relativity principle makes the speed of A with respect to B identical to the speed of B with respect to A for every ordered pair, and asking over what spatial interval the derivative dx/dt is a speed at all.

Wen-Xiu Li, in Problems with the Special Theory of Relativity (2001), pursues a more foundational line: that the relativity principle as Einstein interpreted it conflicts with the uniqueness of the Universe; that the light principle contains a tacit assumption leading to self-contradiction; and that the Lorentz transformation rests not on the light principle but on a general time–space dependence, and has never been shown to be necessary or unique. Zbigniew Modrzejewski revisits the same postulate in A revision of the principle of relativity (2013) by way of thought experiments bearing on the time dilation effect.

Cynthia Kolb Whitney takes up the tension between the two things the theory is asked to do in The Twins, the Mesons, and the Paradox (1997): the prediction appears well validated by the slow decay of rapidly moving unstable particles, and yet leads to a paradox that confounds ordinary logic.

Curtis E Renshaw attacks the assumption underneath the reciprocity in A Test of Relativistic Simultaneity (2016), proposing a concrete test of the relativistic claim that two relatively moving observers instantaneously collocated will see light from a distant event at the same place and time — the assumption embedded in Einstein's train-and-embankment argument, and the one that led to length contraction and time dilation for the moving observer.

The clock paradox

The clock or twin paradox is treated in full in Twin paradox; what follows is the part of the archive that bears specifically on time dilation.

Julio Palacios argued in The Clock Paradox and the Possibility of a New Theory of Relativity (1959, Revista de la Academia de Ciencias Exactas, Físicas y Naturales de Madrid) that the paradox pointed beyond special relativity to the possibility of a new theory of relativity altogether. Franco Selleri reached a comparable conclusion from his own "inertial" transformations in Space and Time Physics with the Lorentz Ether: The Clock Paradox (2004): those transformations, he argued, describe the empirical data better than special relativity does and eliminate the paradox-generating features of the theory by restoring a privileged inertial frame in which the Lorentz ether is at rest.

J W Rush examined the historical record in Einstein's Unsuccessful 1918 Attempt to Resolve SRT's Clock Paradox (2006), noting that by 1918 Einstein had recognised major difficulties in the 1905 theory and published an obscure paper attempting to correct some of them — a paper which, on Rush's reading, does not do the job intended. Steve Brown's "A Note Regarding Relativity" (1991) takes the opposite tack, using what he identifies as a minor error in the 1905 paper to resolve the twin paradox while explicitly presuming the transformation formulae correct.

Peter Hayes approached the controversy as a historian and political scientist. The Ideology of Relativity: The Case of the Clock Paradox (2009) revisits the interwar school of thought that repudiated relativity on grounds of elementary inconsistency. Because some of those critics held extreme right-wing and anti-Semitic views, Hayes argues, their technical objections have been dismissed as scientifically shallow; he investigates the alternative possibility that the critics were right on the technical point, and that relativity overcame them through its strengths as an ideology rather than as a science.

Witold Nawrot offers a reconstruction rather than a refutation in Explanation of twin paradox according to the Euclidean Reality model (2013), in which the four-dimensional Euclidean Reality model is used to show why time dilation is symmetrical for both twins during uniform rectilinear motion, and under what circumstances a dilation is actually measured in one twin's system.

Not every contribution here is critical. Chalmers W Sherwin's Some Recent Experimental Tests of the "Clock Paradox" (1960) argued that the Pound–Rebka measurement of the temperature dependence of the Mössbauer effect in Fe⁵⁷, and the rotating-drum experiment of Hay, Schiffer, Cranshaw and Egelstaff, supplied the first direct experimental verification of the time-keeping properties of accelerated clocks of the kind that occur in the classic clock paradox.

Clock retardation in a preferred frame

The most widely held alternative on this wiki is not that the experiments are wrong but that they measure something else: a physically produced retardation of clock mechanisms moving through a medium or with respect to a preferred frame, leaving time itself untouched. On this view the Lorentz factor is retained and the metaphysics is discarded. See Aether for the medium itself.

Joseph Levy gives the position its clearest statement in Aether-Theory Clock Retardation vs Special Relativity Time Dilation (2008). Assuming an aether not entrained by the motion of celestial bodies, he argues that the readings of moving clocks result from two separate facts: the clocks tick more slowly than in the aether frame because they move through the aether, and the usual synchronisation procedures generate a synchronism discrepancy. Contrary to special relativity, he insists, time itself is not affected by motion.

Thomas G Barnes and Francisco S. Ramirez make the same substitution in Velocity Effects on Atomic Clocks and the Time Question (1982), presenting the experimental and theoretical work of Herbert E Ives as the logical alternative to special relativity. Rotational experiments, they argue, indicate a light-bearing medium and thereby refute the foundations of the theory; relativity's time dilation is replaced by a physically produced clock-rate reduction when clocks move through the reference medium, and the common-sense concept of time is upheld as a fundamental quantity of science.

Chong-Wu Guo reaches the same conclusion by a different route in Research on the Crossed Doppler Effect in Classical Physics (2007), reconstructing the Doppler effect of light in an ether space from momentum conservation and the Planck relation, obtaining a crossed Doppler effect within Newtonian space and time, and concluding that the Larmor–Lorentz hypothesis that clocks moving relative to the ether run slow needs reconsideration.

John-Erik Persson dispenses with the effect entirely. In Dilatory Dilation (2011) he abandons the sound-wave analogy for light in favour of a strict wave model and concludes that time dilation is simply not needed. In two later papers, "Fundamental Error behind Time Dilation" (2019) and "Fundamental Error behind Paradoxes in Physics" (2019), he traces the invention of time dilation to a false interpretation of the Michelson–Morley result and argues that the denial of the ether, together with confusion between wave and particle descriptions of light, is what produced the twin paradox and the other paradoxes of modern physics.

Cameron Rebigsol argues in Relativity Is Self-Defeated (3 of 3): Lorentz Factor, Aberration, and Ether (2016) that the Lorentz factor is an inseparable mathematical consequence of aberration — which he regards as an illusion appearing whenever an observer moves relative to the light source examined — and that a proper analysis of aberration returns one to the ether.

John R Warfield, in The Speed of Light, the "Tic Rate" of Atomic Clocks, and the Earth Centered Inertial Frame (2007), postulates that the Earth-centred non-rotating inertial frame is the preferred frame for both the speed of light and the tick rate of atomic clocks, and that these are two separate processes related only indirectly, through that common frame. See also Speed of Light.

What the atomic-clock experiments actually measure

Hafele–Keating

The most direct challenge came from Domina Eberle Spencer, because she worked from the numbers the experiment never published.

Hafele and Keating reported conclusions but did not publish their raw data. Richard Keating gave the data to Spencer, professor of mathematics at the University of Connecticut, who analysed it with Uma Y Shama and Philip J Mann and published the result as A New Interpretation of the Hafele-Keating Experiment (1996). Their conclusion is stated without hedging:

We have found that an entirely different interpretation of the experimental data, which supports the universal time postulate on the velocity of light, is perfectly consistent with the experimental data obtained by Hafele and Keating. Thus, one of the essential experimental supports of the relativistic theory of time dilation is shown to be invalid.
— Spencer, Shama & Mann, A New Interpretation of the Hafele-Keating Experiment (1996)

The force of the objection lies in what the published result depends on. The experiment's headline claim is an asymmetry between directions — the eastward clocks losing time and the westward clocks gaining it, in amounts said to match the relativistic prediction. Spencer's analysis of the unpublished data is that the readings do not sustain that reading: the flights in the two directions do not differ in the way the relativistic interpretation requires, and the data are equally consistent with her own universal time postulate on the velocity of light, in which there is no reciprocal time dilation to find.

The point is a general one about how the experiment has been used. A result reported as a confirmation, whose supporting measurements were not released for others to examine, is not in the ordinary sense a replicated finding — and Spencer is one of the very few outside the original team to have seen what it rested on.

Spencer presented this analysis on screen in Einstein Wrong - The Miracle Year (2014), David de Hilster's feature documentary, where her examination of the Hafele–Keating raw data is one of the film's central scenes. She appears alongside Ronald R Hatch, who makes the parallel argument about GPS.

Louis Essen — whose own field was caesium time standards — published a short, sharp criticism in Atomic Clocks Coming and Going (1977), objecting that in their theoretical discussion the authors of the flying-clock experiment ignore detailed and fully documented criticisms of Einstein's relativity which had been made and had not been refuted.

Dennis J McCarthy pressed a technical objection in The Hafele-Keating Contradiction (1997). Hafele and Keating, in interpreting their own result, preferred a reference frame having the same angular velocity as the Earth in its orbit; but, as Swift and Pellegrini pointed out in the American Journal of Physics in August 1995, "it is not true that special relativity can be applied if the angular velocity is small enough or the radius is large enough." A more defensible choice of frame, McCarthy argued, produces a contradiction with the theory the experiment is said to confirm.

McCarthy developed the argument into a positive case for the Lorentzian reading in The Orbiting Clock Paradox: Should the Lorentzian View Be Preferred? (1999). Experiments confirm that a circling observer sees a stationary inertial clock at the centre of the circle run fast. For a large enough circle one can always posit a co-moving inertial "lab partner", co-located with and essentially stationary relative to the circling observer for a finite period; the circling observer, using the relativistic Doppler equation, must nevertheless conclude that the central clock runs fast with respect to his own stationary clocks.

GPS and satellite clocks

Satellite navigation is the centrepiece of the case made here, because it is the one application in which clock rates are compared continuously and to very high precision. The argument, made by Percival among others, is that the corrections are computed from each clock's velocity with respect to a single frame — the Earth-Centred Inertial frame — and not from the relative velocity of one clock with respect to another, which is what special relativity's time dilation is a function of. The equation used resembles Einstein's, but the quantity fed into it is an absolute velocity, and choosing a different inertial frame for the calculation would give different and mutually contradictory answers for the same pair of satellites. On this reading the navigation systems are evidence for asymmetric, physical clock retardation with respect to a preferred frame, not for reciprocal time dilation. See GPS.

Viraj Fernando proposes a mechanism for the satellite clock rates in Internal Momentum Changes Manifesting as Clock Rate Changes in GPS Clocks (2009). His complaint is that physical theories have treated bodies as mass points without internal structure, and are therefore unable to consider how the internal energy (mc²) and internal momentum (mc) of a body interact with applied momentum, or how internal momentum functions in gravitational processes. Once those internal changes are made visible, he argues, the clock-rate changes cease to look bizarre.

Ruyong Wang approached the question experimentally. In From the triangle Sagnac experiment to a practical, crucial experiment of the constancy of the speed of light using atomic clocks on moving objects (Europhysics Letters 43, 1998) he takes as his starting point the triangle Sagnac experiment, in which the light travel times between two points A and B in circular motion differ by Δt = 2V_DL/c², and proposes to use atomic clocks on moving objects as a crucial test of the constancy of the speed of light. See Sagnac Effect.

Howard C Hayden examined the rotating-Mössbauer family in Rotating Mossbauer Experiments and the Speed of Light (1992). Champeney's 1963 experiment was performed as a first-order test of ether velocity despite an earlier proof that the ether-velocity effect and the Lorentz time-dilation effect cancel exactly at first order. But, Hayden notes, the experiments show that clock rates are determined by velocity with respect to non-rotating geocentric coordinates, so the first-order time-dilation term reappears and must be balanced by something else if agreement with the measurement is to be recovered.

Carroll O Alley's Investigations with Lasers, Atomic Clocks and Computer Calculations of Curved Spacetime and of the Differences Between the Gravitation Theories of Yilmaz and of Einstein (1994) uses laser ranging and atomic clocks to look for observable differences between Einstein's field equations and Yilmaz's alternative theory of gravitation, noting that the form of Einstein's field equations — in particular the exclusion of the gravitational field's own stress-energy from the source term — is an assumption rather than a derivation.

Mesons, muons and particle lifetimes

The extended lifetime of fast particles is the experimental result most often presented as decisive. Several researchers here accept the measurement and reject the interpretation.

Donald T MacRoberts put the case bluntly in The "Time Dilation" of Mesons Re-Examined (1992): the high-velocity meson experiments at CERN and elsewhere are definite evidence that meson lifetime is a function of velocity with respect to the Earth, and have nothing whatever to do with the time dilation of special relativity. He read them additionally as ether-drift investigations, returning the usual answer — that the Earth's velocity with respect to a fundamental frame is zero.

Thierry De Mees supplies a mechanism in On the Origin of the Lifetime Dilation of High Velocity Mesons (2010). Applying gravitomagnetism (his "gyrotation", the Heaviside–Maxwell analogy for gravity) to fast particles, he finds a physical cause of the lifetime extension in a self-induction effect rather than a delay of time. He notes two further points: that the observed lifetime dilation has been found not to correspond exactly to the predictions of special relativity, and that neither special nor general relativity has ever supplied a physical mechanism at all.

Al F Kracklauer reaches a similar destination from relativistic electrodynamics. In Action-at-a-Distance on the Light Cone (2006) he presents a modified Wheeler–Feynman action-at-a-distance formulation stripped of advanced interaction and of asymmetric ageing, and reports initial results of an analysis of muon-decay time-dilation experiments showing the effect to be a space-time perspective effect that does not contribute to asymmetric ageing — that is, one that does not produce a twin paradox.

Harry Hamlin Ricker surveys the evidence generally in Empirical Verification of Time Dilation in Special Relativity (2011), reassessing the usual reading of the constancy postulate as implying a change in the structure of space and time, and concluding that with respect to the experimental evidence the interpretations offered within special relativity are neither logically consistent nor supported by the facts of experiment.

Deriving the physics without time dilation

A distinct group of contributors does not attack the experiments at all. Their claim is that the working content of relativistic physics can be derived without the kinematic effects, which makes those effects dispensable.

Nizar Hamdan has pursued this programme most systematically. In Abandoning the Ideas of Length Contraction and Time Dilation (2003) he shows that bringing the three-vector Lorentz force law inside special relativity allows the fundamental relativistic equations for a charged particle to be derived without the Lorentz transformation, and hence without its kinematic consequences — length contraction and time dilation. The invariance of the speed of light, he argues, can then be interpreted in a way that does not depend on the properties of space-time. He extends the method in On the Interpretation of the Doppler Effect in Special Relativity Theory (2006), calculating the relativistic Doppler effect from the Lorentz force law and the relativity principle alone, and recovering an intrinsic particle energy that restores compatibility with de Broglie's wave theory.

Kjell Prytz takes a related approach in Force Between Electric Charges: a New Approach to Relativity Theory (2007), introducing relativity from the electric and magnetic forces and deriving time dilation without using the concept of light at all.

Declan Traill models the effect physically rather than eliminating it. On the Quantum-Wave Nature of Relativistic Time Dilation and Length Contraction (2010) explains the kinematic effects of both the special and general theories in terms of the wave nature of matter and light and the way those waves propagate through space, which he offers as a possible route to integrating relativity with quantum mechanics.

Vivian Pope and Anthony D Osborne derive the effect from a different foundation in Orbital Time Dilation (2008). Their Pope–Osborne Angular Momentum Synthesis postulates that all motion is naturally orbital and that orbital angular momentum is holistically conserved; from this they obtain the standard special-relativistic time dilation formula more economically and predict orbital time dilation effects identical to those of general relativity, but without any reference to the Einstein field equations.

Oleg D Jefimenko, author of a well-regarded textbook on electricity and magnetism, treated invariance, length contraction and time dilation as consequences of the electrodynamics of moving charge rather than as postulates about space and time; his approach is discussed in Jefimenko Paper Reviews (2000).

Gravitational time dilation

The gravitational effect attracts a smaller but more pointed literature.

Vyacheslav N Streltsov argues in The Crash of General Relativity: General-Relativistic Time Dilation Contradicts Gravitational Time Slowing Experiments (2001) that general-relativistic time, like special-relativistic time, comes out larger than proper time — and that this conclusion is contradicted by the experiments on gravitational time slowing that are supposed to confirm it.

John Philip Claybourne offers a substitution rather than a refutation in A New Analysis of Time Dilation (1990). He observes that in every experiment in which the moving-clock prediction has been verified, the clocks were subjected to significant accelerations; clocks run slow when accelerated, by the equivalence principle of general relativity, and this predicts results consistent both with special relativity and with the observations. The attraction of the alternative, he argues, is that it is independent of those conclusions of special relativity that have only ever been postulated.

Don Savage pursued an unorthodox experimental line in Measuring Local Time Dilation Using Sandglass Egg Timers (1987), proposing that the effects of time dilation extend some distance out from the system experiencing them, communicated through potential fields such as gravity. He presents data which he reads as showing that certain devices can alter inertial time, as suggesting the existence of "time waves", and as indicating that the phenomenon is at least partly reversible.

Cosmological time dilation

A separate front concerns the claim that the light curves of distant type Ia supernovae are stretched by cosmological time dilation, which is treated as direct evidence for the expansion of the universe.

Ari Brynjolfsson argues that the effect is absent. In Plasma Redshift, Time Dilation, and Supernovas Ia (2004) he shows that conventional physics including plasma redshift fully explains the observed magnitude–redshift relation of the supernovae, with the Hubble constant as the only parameter — against the several adjustable parameters (an initial explosion, a dark-matter parameter, a time-adjustable dark-energy parameter) that the expanding-universe account requires. In Magnitude-Redshift Relation for SNe Ia, Time Dilation, and Plasma Redshift (2006) he extends the analysis to the SNLS data, obtaining a standard deviation of about 0.14 magnitudes from the plasma-redshift curve, and concludes that the data indicate there is no cosmic time dilation and that big-bang cosmology therefore appears false. See Redshift, Dark Matter and Big Bang.

Lyndon E Ashmore reaches the same conclusion from the low-redshift end. Supernovae Ia Light Curves Show a Static Universe (2012) points out that high-redshift light-curve broadening is the only direct evidence for expansion and is routinely used to dismiss Tired Light theories, but that the papers making the argument confine themselves to high redshifts. Reviewing the supernova ageing data at smaller redshifts, and allowing for Malmquist bias and for the fact that intrinsically brighter type Ia supernovae have intrinsically broader light curves, he argues that the mainstream evidence itself points to a static universe.

Experiments claimed to contradict time dilation

Peter Ripota reports a direct experimental challenge in Einstein's Time Dilation Experimentally Refuted (2009). He describes an experiment performed at CERN in 1996 by Antoine Suarez and Valerio Scarani, in which a laser beam was sent into a potassium niobate crystal to produce two entangled beams; one was sent to Bernex and the other to Bellevue, about ten kilometres apart, and the detector at Bellevue was rotated rapidly so that its peripheral velocity approached that of light. A time dilation should have followed; Ripota's account is that the expected effect did not appear.

Michele Barone's "Ritardo degli orologi in moto" (2002) treats the retardation of moving clocks in the volume La Natura del Tempo: propagazioni super-luminali, paradosso dei gemelli, teletrasporto, edited by Franco Selleri.

Researchers on this wiki

Nick Percival — American; foundations of physics; the most sustained analysis here of what the time-dilation data actually show, and of Lorentz relativity as the alternative reading.
Domina Eberle Spencer — American mathematician; analysed the unpublished Hafele–Keating raw data and argued it does not support relativistic time dilation.
Dennis J McCarthy — American researcher; the Hafele–Keating frame-choice objection and the orbiting-clock argument for the Lorentzian view.
Joseph Levy — French theorist; aether-theory clock retardation plus synchronism discrepancy in place of time dilation.
Louis Essen — English physicist and time-standards specialist; early and unyielding critic of the relativistic interpretation of the flying-clock experiment.
Franco Selleri — Italian physicist; inertial transformations and a privileged frame with the Lorentz ether at rest.
Nizar Hamdan — Syrian physicist; derivation of relativistic dynamics from the Lorentz force law, dispensing with length contraction and time dilation.
Ari Brynjolfsson — Icelandic-American physicist; plasma redshift, and the argument that the supernova data show no cosmic time dilation.
Howard C Hayden — American physicist, editor of Galilean Electrodynamics; analysis of the rotating-Mössbauer experiments.
Harry Hamlin Ricker — American electrical engineer; assessment of the empirical case for time dilation.
John-Erik Persson — Swedish electrical engineer; strict wave model of light in an ether, in which time dilation is unnecessary.
Thierry De Mees — Belgian engineer; gyro-gravitation as the physical mechanism of meson lifetime extension.
Cynthia Kolb Whitney — American physicist, editor of Galilean Electrodynamics; the twins, the mesons and the paradox.
Raymond H Gallucci — American nuclear engineer; time dilation as an apparent effect.
Peter Hayes — British academic; the clock paradox as a case study in the ideology of relativity.
Ruyong Wang — Chinese-American physicist; Sagnac-based crucial experiments with atomic clocks on moving objects.
Julio Palacios — Spanish physicist; the clock paradox as grounds for a new theory of relativity.
Chalmers W Sherwin — American physicist; the Mössbauer experiments as verification of the time-keeping of accelerated clocks.
Kjell Prytz — Swedish physicist; time dilation derived from the forces between charges, without the concept of light.
Declan Traill — Australian researcher; quantum-wave model of the kinematic effects.
Vivian Pope and Anthony D Osborne — British; orbital time dilation from the Pope–Osborne Angular Momentum Synthesis.
Lyndon E Ashmore — British physics teacher; supernova light curves and the static universe.
Vyacheslav N Streltsov — Russian physicist; general-relativistic time dilation against the gravitational time-slowing experiments.
Al F Kracklauer — German researcher; muon time dilation as a perspective effect without asymmetric ageing.
Viraj Fernando — Sri Lankan-Canadian independent researcher; internal momentum as the source of GPS clock-rate changes.
Curtis E Renshaw — American electrical engineer; a proposed test of relativistic simultaneity.
Donald T MacRoberts — American researcher; meson lifetimes as a function of velocity relative to the Earth.
John R Warfield — American physician; the Earth-centred inertial frame as preferred frame for light speed and clock rate.
Carroll O Alley — American professor; laser and atomic-clock tests distinguishing the Yilmaz and Einstein gravitation theories.
Wen-Xiu Li — Chinese researcher; foundational problems with the relativity and light principles.
Chong-Wu Guo — Chinese researcher; the crossed Doppler effect in an ether space.
Oleg D Jefimenko — Ukrainian-American physicist; electrodynamic treatment of invariance, contraction and dilation.
Michele Barone — Greek experimental physicist; the retardation of moving clocks.
John Philip Claybourne — American researcher; acceleration and the equivalence principle as the alternative explanation.
Don Savage — American researcher; local time dilation experiments and "time waves".
Peter Ripota — Austrian physicist and author; report of the Suarez–Scarani entangled-photon experiment.
Zbigniew Modrzejewski — Polish-Canadian philosopher; revision of the principle of relativity.
J W Rush — American researcher; Einstein's 1918 attempt on the clock paradox.
Allen D Allen — reciprocity of speed and the spatial interval over which dx/dt is a speed.
Thomas G Barnes — American professor of physics; clock-rate reduction in a reference medium, following Herbert E Ives.
Witold Nawrot — Polish researcher; the Euclidean Reality model of the twin paradox.
Cameron Rebigsol — Chinese-American researcher; the Lorentz factor as a consequence of aberration.