Weak Relativity: The Physics of Space and Time Without Paradoxes

Weak Relativity: The Physics of Space and Time Without Paradoxes
Author	Franco Selleri
Published	2009
Pages	174

Weak Relativity: The Physics of Space and Time Without Paradoxes (2009) is a book by the Italian theoretical physicist Franco Selleri (1936–2013), presenting at book length the argument he developed over his final two decades: that absolute simultaneity can be restored to physics without contradicting any experiment, by making a different but empirically equivalent choice of clock synchronisation. The result, he holds, is a "weakened" relativity — one that keeps the tested predictions of Einstein's theory while discarding what he regarded as its paradoxes.

The book is the extended statement of the case set out more briefly in his paper "Eight Proofs of Absolute Simultaneity".

The argument

The parameter e₁

Selleri's whole programme turns on a single quantity. In the transformation of time between inertial frames, the coefficient of the space variable x — which he calls e₁ — fixes the convention by which distant clocks are synchronised. Einstein's choice, standard special relativity and the Lorentz transformation, corresponds to one value of e₁ (giving the relativity of simultaneity). Selleri argues that e₁ is conventional: it can be changed without altering any empirical prediction of the theory, because it concerns only how clocks are set, not what they read when brought together.

Setting e₁ = 0 yields what Selleri calls the "inertial transformations": these reproduce the measured relativistic effects — length contraction, time dilation, the Sagnac effect — but restore absolute simultaneity and a preferred frame. The book's six central chapters each carry "e₁ = 0" in their titles and offer largely independent arguments for that value, drawn chiefly from phenomena on accelerating and rotating systems, where Selleri contends the symmetry between frames visibly breaks down.

Consequences

Selleri argues that the Sagnac effect and related rotating-platform experiments "converge in a strong indication of the value e₁ = 0", implying absolute simultaneity and a new structure of space and time. He also draws cosmological consequences that, he writes, "go against the big bang model". His conclusion is deliberately measured: "after our results relativism, although weakened, is not dead, but survives in milder forms."

Assessment

Selleri was among the most technically serious critics of relativity's foundations, and the mathematics of this programme is clean — the central Sagnac derivations and the properties claimed for the inertial transformations check out. The starting observation is also correct and is not heterodox: the conventionality of distant simultaneity is a real feature of special relativity, discussed by Reichenbach, Grünbaum and others, and e₁ genuinely is a synchronisation parameter that can be varied without changing round-trip observables. To this extent Selleri is on solid ground, and his insistence on it is a service.

The difficulty is that this same fact undercuts the conclusion he draws from it.

Empirical equivalence works both ways. If e₁ = 0 and Einstein's value give identical predictions for every measurement — every fringe count, every clock read at a meeting point — then no experiment can select between them, and that includes the experiments Selleri offers as proofs. The Sagnac and rotating-platform results are agreed by all parties; deriving them from an anisotropic light speed in a rotating frame is a re-description of the same geometry, not a discriminating test. Agreement here is agreement with everyone.

The Sagnac "proof" rests on a topological fact relativity already contains. The reason a rotating rim cannot be Einstein-synchronised all the way round is that the synchronisation fails to close, leaving a gap of 2ΩA/c² at the seam — which is exactly the standard account of the Sagnac effect. Selleri's "discontinuity at zero acceleration" is that non-closure stated differently; it is a property of rotating coordinates, not evidence that inertial frames have absolute simultaneity. Relativity does not predict a null Sagnac effect, so reproducing a non-null one refutes nothing.

Some proofs recover standard results, and one assumes the conclusion. Two of the arguments derive corrections (the 2ΩA/c² term, R. Wang's conveyor delay) that ordinary relativity gives in the Earth-centred inertial frame. The appeal to Bell's spaceships infers, from two clocks accumulating equal delay as reckoned in the preferred frame, that events simultaneous there are simultaneous in the moving frame — which is the relativity of simultaneity being denied rather than disproved.

The deepest point is one Selleri half-concedes when he quotes Ronald Hatch approvingly: the Lorentz transformations are "inertial transformations combined with clock biases." If the two frameworks differ only by a resetting of clocks, they agree on every physical coincidence, and the choice between them is precisely the convention Reichenbach described. Selleri exhibits a synchronisation he finds more natural and a preferred frame which — as he acknowledges — "we are presently unable to identify"; he does not exhibit a measurement that separates his scheme from Einstein's. The programme is internally consistent and cleanly argued, but it does not escape the conventionality thesis it sets out to overturn.

What can be said firmly is that Weak Relativity is the opposite of crankery: a careful, honest exploration of a genuine freedom in the theory, whose value lies in making that freedom explicit even if the strong conclusion does not follow.

The argument

The parameter e₁

Consequences

Assessment

See also