Standing Wave Interferometry

What kind of paper this is

"Standing Wave Interferometry" is a short article by H. Aspden published in Physics Essays volume 3, number 1 (1990), pages 40–45. It is not an experimental report and it presents no new measurements of its own. It is an interpretive and programmatic paper: it takes an existing experimental anomaly — the Silvertooth experiment, briefly reported in 1986 — and offers a causal physical explanation for it, then argues that the same physical picture opens the door to a new class of light-speed test that the classical Michelson–Morley design could not perform.

The abstract states the thesis plainly: energy in standing waves may affect the component wave velocities, the Silvertooth result may be explicable on that basis, and the technological implications are consequential enough to warrant further investigation. The paper's own keywords are ether detection, the Silvertooth experiment, and standing waves.

For a reader working through the Aspden material in this collection, the paper is worth attention for three reasons. It is a distinct work, separate from the energy and aether arguments covered elsewhere. It makes a sharp methodological distinction — first-order versus second-order sensitivity to v/c — that determines whether a proposed test is feasible or nearly undetectable. And it contains an explicit concession that limits Aspden's own programme, which is useful context when reading his more confident claims in other papers.

The core argument

Aspden's starting picture is that the ether behaves like a fluid crystal. The space lattice that sets the local electromagnetic reference frame is nucleated on matter and shares the observer's motion, so light speed can be locally constant for a non-accelerated observer while an absolute frame still exists in regions devoid of matter. Both the classical ether proposition and Einstein's constant-light-speed proposition can then be true at once, on this reading, because the local frame is not the cosmic one.

From that picture he draws an experimental question. A machine that shares the Earth-bound observer's essentially non-accelerated motion, but whose internal parts are strongly accelerated, might disturb the local space lattice and dissolve its connection with the observer. Alternatively, an intermediate region might form inside the accelerated zone — an in-fill lattice seated in an independent frame, identified with the absolute or cosmic background frame. This is what gives reason, in Aspden's account, to probe the true light-speed reference frame in vacuous space.

A further step follows from the fact that we sit on a rotating, and therefore accelerated, Earth. Aspden asks whether the degree of acceleration needed to dissolve the fluid lattice in such intermediate regions depends on electromagnetic standing-wave energy. If standing-wave energy has sufficient presence and shares the translational motion of an enclosing apparatus, it may encourage the formation of a bridging lattice locked into common motion with the apparatus. The consequence he draws is that standing-wave conditions may invalidate interferometric tests of motion through an absolute frame. He is candid that these are speculative issues that would not warrant special attention but for certain experimental anomalies needing explanation — the Silvertooth result being one, and a gravitational-action theme being another that the paper sets aside.

First-order versus second-order sensitivity

This is the load-bearing methodological point of the paper. Michelson–Morley-type tests detect anisotropy at second order in v/c: the effect scales with (v/c)² and is therefore extremely small. Aspden argues that even a modified Michelson–Morley apparatus designed to avoid standing-wave overlap would yield only second-order evidence, difficult to detect unless the apparatus and conditions are special.

The laser, in his account, changes the situation. On the same physical basis it permits a direct first-order sensing of v/c — an effect proportional to v/c itself, and therefore far larger. The claim is explicitly conditional: if the standing-wave condition forces local light speed to be isotropic relative to the apparatus frame, while free waves travel at a speed isotropic in the preferred frame, then a first-order measure in v/c simply has to be a possibility. The antecedent is the speculative part; the consequence is the experimental proposal. Aspden credits the suggestion of such an experiment to himself and describes it as arising from collaboration with Silvertooth, who was then doing preparatory design work for a conclusive test first briefly reported in 1986.

The Michelson–Morley configuration objection

Aspden makes a specific technical objection to the standard reading of Michelson–Morley. Experimenters align the apparatus by looking for distinct spots where light strikes the reflection surface, and they place those spots as close together as possible. With plane mirrors, the rays must pass through one another in opposite directions over a significant range of the mirror separation, and the closer the spots, the greater the overlap of oppositely moving rays. He notes the subtlety that a reflected ray reaching the halfway position becomes an incident ray entering the path of its own future reflection.

His conclusion is that a mirror configuration designed to avoid standing-wave conditions — his Figure 1, captioned as a Michelson–Morley apparatus modified to avoid standing wave conditions — is not superfluous but essential if the accepted interpretation of the Michelson–Morley experiment is to be held. This is an argument about how the classical experiment should be interpreted, not a new measurement, and it should be read as such.

Silvertooth's experiment and its separate motivation

Silvertooth built a nonrotating Sagnac configuration with a linear path section and scanned a detector through that path, looking for a v/c effect that might have eluded Michelson and Morley. Aspden is explicit that Silvertooth was not thinking in terms of energy interactions affecting wave velocity components in standing waves. Silvertooth's motivation came from a concern that the Sagnac effect, as used in ring laser gyros, had empirical implications when examined against the Michelson–Morley null result. The principles involved in the Sagnac effect are the same as those in the Michelson–Gale experiments detecting Earth rotation.

The sensor was fabricated from standard image-orthicon parts by General Electric in the United States. It measured the intensity of a standing-wave beam passing through a 500 Å thickness of a photocathode — a photosensitive coating on a transparent aperture, much thinner than the laser wavelength, which is what allows scanning along the standing wave. The energy-velocity mechanism is Aspden's causal account, offered as one possible explanation among others; he notes that relativistic accounts have also been attempted, though one such account implies that the photon may have mass.

The Sagnac tension and Langevin's interpretation

Aspden observes that the Sagnac interferometer senses rotation of the apparatus relative to an inertial frame, which conforms with ether predictions. The relativistic defence, following Langevin, treats the Sagnac result as consistent with the Foucault pendulum or gyroscope and explicable within general relativity. Aspden's counter is that standing waves in the Sagnac interferometer are not locked to the mirror surfaces, because 180-degree reflections are avoided, so the question remains open for clarification by experiment. This is a claim about what remains experimentally undecided, not a demonstration that the relativistic account fails.

Reinterpreting the null results

Two prior results are re-read as consistent with the preferred-frame picture.

Cialdea's one-way test. Cialdea used 90-degree mirror reflections and no standing waves in the test path, and obtained a null result widely reported as new proof of Einstein's theory. Aspden argues that Cialdea used two lasers at the same frequency while reorienting them, and that the small relative movement of these wave-resonant lasers developed a phase shift that exactly cancels the anisotropy effect. This was the basis on which Tyapkin discredited experiments of that kind. Crucially, Aspden argues the Tyapkin criticism cannot apply to Silvertooth's single-laser test, because Silvertooth moves the photodetector and the standing-wave light system is unaffected by that motion.

Pre-laser experiments. Aspden argues that frequency fluctuations in early light sources would momentarily preclude the in-phase standing-wave oscillation that overrides sensitivity to the v/c response, allowing partial anisotropy to appear spuriously rather than systematically. He notes that Kennedy and Thorndike observed a daily variation as the Earth rotated, commensurate with motion through space of 24 km/s, though almost entirely swamped by uncertainty — a figure they themselves dismissed beside the thousands of km/s known to exist among the nebulae. Aspden finds it significant that inconsistent indications of anisotropy reported by many observers vanished once laser frequency stability was achieved, and surprising that the onset of standing-wave resonances during transient periods of frequency stability was not treated as a causal physical factor.

He also acknowledges a conceptual difficulty for readers: that a light wave can have separate components of the same frequency travelling in the same direction at slightly different speeds, one referenced on the local energy field and one on an independent frame. This is what he has advocated, on the basis that one component is part of the standing wave system.

The concession that limits the programme

Aspden concedes that the Cialdea null result is consistent with free motion of light referenced on a preferred frame, provided lasers and atomic clocks suffer frequency effects according with the time-dilation formula with v referenced on that preferred frame. He calls this the fascinating aspect of the theory of relativity: even if the preferred frame can be detected optically, relativity will still contribute its time-dilation feature. The practical payoff of detecting the ether is therefore reduced — detection would not remove relativistic time dilation — even though the theoretical claim about the preferred frame survives. This is a genuine self-limitation and should be given weight when reading Aspden's more expansive claims elsewhere.

What the available text does not contain

Three limits should be kept in view.

1. Two text gaps. The available text contains two explicit markers indicating intervening text was not supplied: one in the introduction, interrupting a sentence about gravitational action interpreted in a manner unifying it with electromagnetic fields, and one near the end, interrupting a sentence about a composite wave adopting an intermediate compromise speed. The content of these passages is unavailable and is not reconstructed here. The gravitational-action tangent and the intermediate-compromise speed argument may contain additional claims.
2. No replication evidence. Whether Silvertooth's 1986 Nature result has independent replication is not addressed in the available text.
3. No conclusion section. The paper's own conclusion beyond the abstract is not present.

The extracted text also contains garbled forms such as "stongly," "modem," "indeperident" and "Vefficet," which should be treated as scanning artifacts rather than meaningful terms.

How to read it alongside the rest of the Aspden material

This paper is a companion to the other Aspden works in the collection: the Power From Magnetism material, Modern Aether Science, and Aether Science Papers. Where those argue for the reality and properties of the aether, this one takes the aether's preferred frame as a target of measurement and asks what kind of experiment could detect it. The preferred-frame and time-property themes also run through the Kozyrev dossier, though the arguments and evidence there are different and should not be merged with Aspden's.

The paper's treatment of an unexplained anomaly as requiring a causal account connects to broader questions about separating claims from measurements. Aspden's own framing — speculative issues that would not warrant special attention but for certain experimental anomalies that need explanation — is a useful reminder that the argument is programmatic rather than closed, and that the standing-wave mechanism is offered as one candidate explanation among several.