Difference between revisions of "Ring Laser Gyroscope"
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We are told 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 could be possible for an observed rotation rate of 15 degrees per hour beneath a device to be an "oscillation in the gain medium." | We are told 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 could be possible for an observed rotation rate of 15 degrees per hour beneath a device to be an "oscillation in the gain medium." | ||
− | This confirms that that the matter is actually a measurement of anthropogenic and microseismic noises, and not a direct and undeniable measurement of rotation beneath the device as some have alleged. The researchers in such papers | + | This confirms that that the matter is actually a measurement of anthropogenic and microseismic noises, and not a direct and undeniable measurement of rotation beneath the device as some have alleged. The researchers in such papers do not appear to be asserting that claim themselves. |
==Calculation Agreement== | ==Calculation Agreement== |
Revision as of 07:43, 21 February 2019
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 Ring Laser Gyroscope 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).
Some have alleged that Ring Laser Gyroscopes have detected the rotation of the earth. When assessing these claims, it is found that modern Ring Laser Gyroscopes are very sensitive devices which are often double-purposed as seismometers. These sensitive devices resort to detecting patterns in the background microseismic noise, where certain features are interpreted to be caused by the earth's rotation. The feature of the background noise assumed to be an effect of the earth's rotation is called the "Earth line," and is admitted to be of unknown origin and cause.
The Earth Line
Strapdown Inertial Navigation Technology
By David Titterton, John L. Weston, John Weston
From Chapter 15.6 (Archive) on p.497 we see that the rotation of the earth is seen with "the Earth line":
“ The Fourier transform of the output from the laser cavity gives a spectral line associated with the rotation of the Earth often termed 'the Earth line'. Analysis of this spectral line is used to monitor the impact of seismic waves and other events. This ability to make high-precision measurements of rotation rates has led to applications in geodesy. ”
Analysis of the Earth line is used to monitor seismic events. On p.498 we read that the Earth line is around the 0.2-1Hz region:
“ The effect of seismic events is to induce frequency-modulated side bands, in the 0.2-1 Hz region, around the 'Earth line', which indicate the presence of rotational components associated with seismic events. ”
We also read that seismic events around that region is assumed to indicate the presence of rotational components associated with seismic events.
Oscillation in the Gain Medium
In Ring Laser Dynamics (Archive) by B Tom King it is admitted that the nature of the 'Earth line' is unknown and unverified. From p.152 we read:
“ While lasing in single longitudinal mode and unlocked under the Earth's rotation a Lissajous figure is generated on an oscilloscope with the Sagnac signal from G0 on the x-axis and a sinusoid (from a signal generator) on the y-axis. The figure can be made stationary by varying the frequency of the generated signal. Once achieved this becomes an extremely sensitive detector of phase shifts in the G0 output. A variety of tests can then be performed. Artificial seismic events are easily detected as a jitter in the Lissajous figure. Also the introduction of a magnetic field near the gain medium has the effect of shifting the beat frequency and hence causes the Lissajous figure to rotate at a constant rate. However, the question remains as to whether or not this signal is necessarily the Earth induced line. It is difficult to impose a rotation on the laser as it is rigidly mounted to a solid concrete wall which in turn is moulded around the solid volcanic rock that forms the interior cavern wall. It is conceivable that the signal can be traced back to some oscillation in the gain medium. This problem is yet to be clarified. ”
We are told 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 could be possible for an observed rotation rate of 15 degrees per hour beneath a device to be an "oscillation in the gain medium."
This confirms that that the matter is actually a measurement of anthropogenic and microseismic noises, and not a direct and undeniable measurement of rotation beneath the device as some have alleged. The researchers in such papers do not appear to be asserting that claim themselves.
Calculation Agreement
The author of the above paper 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.
“ However, it is assumed that the signal is indeed the Earth induced rate mostly because of the excellent agreement between the measured output frequency (see Figs. 6. 7 and 6.8) and the expected frequency of 287. 75 ± 0.46 Hz. ”
"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 process is using a predefined period to assess a daily variation or feature of the noise to get a "rotation rate".
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.
Seismic Wave Propagation
Q: If the Ring Laser Gyroscope is assessing seismic noise in the attempt to observe the earth's rotation, how is it that Ring Laser Gyroscopes on airplanes can see the rotation of the earth?
A. Not all types and sizes of Ring Laser Gyros claim to be capable of observing the rotation of the earth. It is unclear whether those types of RLGs can see the earth's rotation. However, seismic and anthropomorphic noise can propagate through the air and does not necessarily only originate from within the earth. Other possible sources for the noise are the daily changes of the atmosphere or influence from the celestial bodies. In the atmosphere seismic waves take the form of sound waves.
Background Seismic Noise
From http://microglacoste.com/gPhoneNoise/gPhoneSeismicNoise.pdf (Archive) we read:
“ It is interesting to speculate on the precise origin of the background seismic noise. Haubrich et al ii for example, open their article with the following description of the seismic noise background and the large interest it has generated over the years as well as the intractability of its investigation:
The low‐level background unrest of the earth, called microseisms or earth noise, has puzzled seismologists and other scientists for nearly a century. The problem of its nature and causes has proved particularly unyielding, not, however, for lack of investigation. A bibliography covering work up to 1955 [Gutenberg and Andrews, 1956] iii lists over 600 articles on the subject; one covering the years from 1955 to 1964 [Hjortenberg, 1967] iv lists 566. Unfortunately, much of this work has advanced the subject but slightly. ”
Airborne Transmission
https://en.wikipedia.org/wiki/Seismic_wave (Archive)
“ Primary waves (P-waves) are compressional waves that are longitudinal in nature. P waves are pressure waves that travel faster than other waves through the earth to arrive at seismograph stations first, hence the name "Primary". These waves can travel through any type of material, including fluids, and can travel nearly 1.7 times faster than the S waves. In air, they take the form of sound waves, hence they travel at the speed of sound. Typical speeds are 330 m/s in air, 1450 m/s in water and about 5000 m/s in granite. ”
https://amp.livescience.com/24209-earthquakes-infrasound.html (Archive)
“ As earthquake waves ripple through the Earth, the crust buckles, rumbles and roars — both audibly and at infrasonic frequencies, below the range of human hearing. A new study finds the Earth's surface acts like a speaker for low-frequency vibrations, transmitting an earthquake's infrasonic tumult into the air. ”