Earth rotation and resonator tests: what SPHERE can learn

The related research

Humboldt University describes a modern Michelson–Morley experiment using two orthogonal optical cavities in one fused-silica block. Lasers locked to the cavities were compared through a beat measurement while the apparatus rotated on a precision turntable.

The researchers describe how a hypothetical anisotropy could produce a turntable-rate modulation whose amplitude changes with Earth’s rotation and orbit. Their analysis uses a specified test theory rather than treating any daily pattern as evidence of an unexplained effect.

Our response: do not confuse direction with place

Moving a sphere often changes its orientation, beam angle, mounting strain and thermal contact. If an A/B trial changes several variables, a residual cannot cleanly be assigned to position. The expanded design should include rotation-only controls, handling-only sham trials and channel swaps.

Simultaneous four-object measurement provides a same-window snapshot, but a snapshot alone cannot estimate a daily or seasonal modulation. Repeat observations across time and preserve orientation metadata. Keep exploratory time-pattern searches separate from the preregistered primary A/B analysis.

What to record

• UTC acquisition start, duration, clock source and timing uncertainty.
• Object coordinates in a named local frame, relative heights and orientation.
• Channel identity, target point, fixture configuration and excitation settings.
• Temperature gradients, vibration diagnostics and relevant environmental logs.
• Randomization code, settling criterion and immutable analysis version.

If a celestial model is proposed, state the coordinate transform and ephemeris used. Do not simply add scalar rotation, orbital and galactic speeds: velocity is frame-dependent and directional. The model must specify what measurable modulation follows and why.

Further issues: periodic artifacts

HVAC schedules, room occupancy and electronics warm-up can also correlate with time of day. Repeating trials on different days, logging conditions and conducting sham controls help test these alternatives. A pattern matching a chosen period after extensive searching needs correction for the search process and prospective replication.

Questions for engineers and skeptical readers

Have you diagnosed a daily pattern in an instrument? Was the cause environmental, mechanical or software timing? What controls separated those explanations? Would you add a rotation-only block before expanding to multi-site experiments?

Continue the design review

• Synchronized measurement research hub
• Does Earth’s motion affect resonance measurements?
• Synchronized four-object frequency measurement protocol
• Frequency measurement error budget: timing, drift and false positives
• What a miniature clock network teaches SPHERE about synchronized measurements
• Hardware for synchronized resonance measurements
• Community review: how would you improve the experiment?
• Current draft LOC-1 protocol