Will a moving mirror produce light that propagates below c in vacuum by the end of 2030?

Question

I propose an experiment to test whether reflection from a moving surface changes light’s propagation speed in vacuum.

A laser reflects from the rim of a rotating disk, with the reflected beam travelling approximately opposite to the local direction of the rim’s motion, towards a detector. The reflecting surface is therefore moving away from the detector.

My model, Matter as Machine, predicts an outgoing speed of approximately c − 2v, where v is the rim’s local speed, under the simplified assumptions described in the proposal.

The experiment would compare reference pulses with reflected pulses at different rotation speeds and propagation distances. This would help distinguish a propagation-speed change from changes in optical path length or apparatus timing.

Read the proposed experiment and prediction:(https://matterasmachine.com/articles/predictions/slow-photons).

If confirmed and demonstrated to be incompatible with special relativity, this effect would constitute evidence against the theory. Such a discovery could be Nobel Prize-worthy, potentially bringing recognition to those who carry out and establish the result. Neither the outcome nor a prize is guaranteed.

Resolution criteria

Resolves YES if, by 31 December 2030, 23:59 UTC, publicly available results from this experiment or an equivalent moving-reflector experiment demonstrate:

- An outgoing propagation speed below c in vacuum that depends on the reflector’s motion.

- An additional delay that increases with post-reflection propagation distance, after accounting for optical path-length changes.

- Independent replication, with reported uncertainties sufficient to distinguish the effect from measurement error.

A delay attributable solely to known spatial-structure effects, optical components, detector response or changing path length does not qualify.

The result need not match c − 2v exactly. This market concerns the existence of the specified slowdown, not confirmation of the entire Matter as Machine model.

Resolves NO otherwise, including if no qualifying experiment is completed or the results remain inconclusive by the deadline.

Disclosure

I developed Matter as Machine and proposed the linked experiment. The prediction has not been experimentally confirmed.

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Manifold Markets · Answer

Unlikely — Manifold Markets prediction market estimates a 9% chance (8 traders, as of Nov 1, 2026).