Ring Laser Gyroscope

The Ring Laser Gyroscope is a type of gyroscope that is based on laser beams which move around a cavity. The principle of operation of a RLG is based on the Sagnac Effect, which was famed for showing that light changes velocity on a rotating platform. The changing velocity of light as seen in the RLG and Sagnac Experiments is said to be contrary to the consistency of light as proposed by Special Relativity (See the Michelson-Morley Experiment and Sagnac Experiment).

In the Ring Laser Gyroscope two counter-propagating laser beams are shown to have different frequencies with the difference dependent on rotation rate. Measurements of this difference provides the rotation angle or rotation rate about the RLG's sensitive axis.

Some have alleged that Ring Laser Gyroscopes have detected the rotation of the earth. When assessing these claims closer, it is found that modern Ring Laser Gyroscopes are very sensitive devices which are often double-purposed as seismometers. These sensitive devices are interpreting patterns in the background microseismic noise as the earth's rotation.

The Earth Line
Strapdown Inertial Navigation Technology By David Titterton, John L. Weston, John Weston

From Chapter 15.6 on p.497

p.498

University of Canterbury
In a PhD thesis by B Tom King it is admitted that the nature of the Earth induced line is unknown and unverified. From p.152 we read:

It is admitted that the nature of the earth line is unknown and that the signal may be traced back to some oscillation in the gain medium. The reader may ponder how it would be at all possible for a directly observed rotation rate of 15 degrees per hour beneath a device could be traced back to an "oscillation in the gain medium", and why it is called a "signal". This confirms that that the matter is actually a measurement of anthropogenic and microseismic noises, and not a direct measurement of rotation beneath the device as some have alleged.

The author goes on to deduce that because the earth induced line agrees with an equation, it is assumed that the rate is indeed from the earth.

"Excellent agreement" with an equation which was likely made to match observation, after the fact, and after the invention of the device.

On p.152 where the paper discusses the theory of the equations, it is shown that the rotation rate of the earth involves the period of 86164s applied to the interpetation, which is the Sierael Day. The equation is using a predefined period to assess a daily variation in the noise.



The 'Sidreal Day' happens to be the time it takes for the sun, stars, and celestial bodies to return to their spots above the earth. This is opposed to the Solar Day, which is supposedly the true rotation of the earth, and is in regards to the sun.

Background Noise
From http://microglacoste.com/gPhoneNoise/gPhoneSeismicNoise.pdf we read:

Airborne Transmission
https://en.wikipedia.org/wiki/Seismic_wave

https://amp.livescience.com/24209-earthquakes-infrasound.html