Empirical Earth · Rotation & How We Measure It

The rotating optical resonator — a sealed box that finds the spin axis

The claim

“Ring lasers see some rotation and calling it the Earth’s is just an assumption.”

What is measured

A closed optical loop splits the resonant frequency of its clockwise and counter-clockwise light when it turns. Bolt it to bedrock and it reads a steady 7.292×10⁻⁵ rad/s, projected onto the loop by the latitude. The apparatus is sealed, needs no view of the sky, and returns a direction as well as a rate.

What would show this is wrong

horizontal ring lasers at widely separated latitudes reading the same rotation rate, or a resonator whose beat note fails to reverse when the apparatus is inverted, or three orthogonal rings that cannot be reconciled to a single common rotation vector.

Sources

  1. Belfi, J. et al. (2017). Deep underground rotation measurements: GINGERino ring laser gyroscope in Gran Sasso. A 3.6 m square ring laser 1,400 m beneath the mountain, resolving tens of picor link
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