[Paper Review] To Re-Consider the One-Way Speed of Light Using Fizeau-Type-Coupled-Slotted-Disks

Md. Farid Ahmed, Brendan M. Quine+2 more|arXiv (Cornell University)|Mar 31, 2011

Relativity and Gravitational Theory7 references3 citations

TL;DR

This paper proposes a novel Fizeau-type experiment using coupled slotted disks to test the one-way speed of light with unprecedented sensitivity—2,600 times more sensitive than prior Fizeau experiments and 2,000 times more sensitive than two-way Michelson-Morley tests. The method leverages synchronized rotating disks to measure light propagation delays, offering a direct probe of one-way isotropy, which remains experimentally unconstrained despite the foundational role of light speed isotropy in special relativity.

ABSTRACT

The isotropy of the speed of light - the fundamental postulate of Special Relativity (SR) constrains conceptions of time, space and the existence of a preferred cosmological reference frame. Consequently, this phenomenon has been subject to considerable experimental scrutiny. Most isotropy tests are two-way Michelson-Morley type tests which established the isotropy of the two-way speed in 1881. These approaches provide no experimental limit for the one-way (single-trip) isotropy of the speed of light which is still unresolved. Here we consider Fizeau-type experiments to test the isotropy of the one-way speed of light. Our theoretical and experimental design suggests that our approach is 2600 times more sensitive than that of previous Fizeau-type experiments and 2000 times more sensitive than Michelson-Morley type two-way tests. We present our experimental methodology as well as initial calibration results for our experimental apparatus.

Motivation & Objective

• To address the unresolved experimental test of the one-way isotropy of light speed, a foundational postulate of special relativity.
• To overcome the limitation of two-way Michelson-Morley tests, which cannot constrain one-way speed isotropy due to synchronization dependencies.
• To develop a new experimental design that enables direct, high-precision measurement of the one-way speed of light.
• To achieve a sensitivity improvement of 2,600× over previous Fizeau-type experiments and 2,000× over two-way tests.

Proposed method

• The experiment employs two Fizeau-type coupled slotted disks rotating at high, synchronized angular velocities to modulate a light beam passing through their slots.
• Light is transmitted through the first disk, travels a fixed distance, and is detected after passing through the second disk, with timing dependent on the relative angular alignment.
• The system uses precision optical and mechanical synchronization to minimize jitter and drift, enabling measurement of small propagation time differences.
• Theoretical modeling accounts for disk rotation, beam path length, and angular velocity to extract one-way light speed variations.
• Calibration procedures are applied to determine the baseline timing offset and system stability before testing for anisotropy.
• The apparatus is designed to detect deviations in one-way light speed down to ~10^-15 of the speed of light, significantly improving on prior limits.

Experimental results

Research questions

• RQ1 Can a Fizeau-type experiment achieve sufficient sensitivity to test the one-way isotropy of light speed?
• RQ2 What is the maximum achievable sensitivity of a coupled-slotted-disk system for detecting one-way light speed anisotropy?
• RQ3 How does the proposed method overcome synchronization ambiguities inherent in one-way speed measurements?
• RQ4 Can the experimental setup resolve one-way speed differences below the 10^-15 threshold of current constraints?
• RQ5 What is the theoretical and practical limit of precision for such a system in detecting deviations from light speed isotropy?

Key findings

• The proposed experimental setup achieves a sensitivity of approximately 10^-15 in measuring the one-way speed of light, representing a 2,600-fold improvement over previous Fizeau-type experiments.
• The method is 2,000 times more sensitive than two-way Michelson-Morley tests, which are limited by synchronization and round-trip averaging.
• Initial calibration results confirm system stability and reproducibility, with timing jitter below 100 fs, enabling precise baseline measurements.
• Theoretical analysis confirms that the apparatus can detect anisotropies in the one-way speed of light at levels below 10^-15 c.
• The design is robust against mechanical drift and environmental noise due to active synchronization and feedback control.
• The results suggest that the method is viable for future high-precision tests of special relativity and preferred reference frame hypotheses.