Frankly, the wiki gets this bass ackwards. It also mentions a fictitious "vibrating gravity theory" – where did that derp come from?
That is expressly described in the Wiki. The gravimeter is a seismometer which is detecting "gravity waves". Immediately prior to the Corrections for Latitude section there is the section Gravity Wave Theory
Gravity Wave Theory
A study titled Seafloor Compliance Observed by Long-Period Pressure and Displacement Measurement uses gravimeters to study the gravity of the ocean. On p.2, para.4 its authors call the gravimeter a long-period seismometer...
Do you ever read and try to understand the material you cite? The "Seafloor Compliance" study is about deformation of the sea floor under pressure from water waves. You have read the terms "gravity wave", "infragravity wave" and "ultragravity wave" and thought this must be how gravity is detected, but nowhere in that study is measuring acceleration due to gravity even mentioned, nor is a measured gravitational acceleration given. The extensive quoting from Wikipedia is irrelevant. Your cherry-picking has yielded ... a zucchini. How disappointing.
And then we have another citation:
... This paper below describes both absolute and relative gravimeters, and then goes on to say that "gravimeters do not give direct measurements of gravity". This means that neither kind of gravimeter is measuring gravity directly.
https://gogn.orkustofnun.is/unu-gtp-sc/UNU-GTP-SC-16-13.pdf
3.4 Measurements of gravity
There are two kinds of gravity meters. An absolute gravimeter measures the actual value of g by
measuring the speed of a falling mass using a laser beam....
....
3.6 Reduction of data
Gravimeters do not give direct measurements of gravity; rather, a meter reading is taken which is then...
So absolute gravimeters measure the actual value of g, but gravimeters do not give direct measurements of gravity? You're not making sense.
I could produce references and citations about relative and absolute gravimeters, what they measure and how they measure it, but I expect we'll get into a round of "he said, she said" so let's consult the people who ought to know; the gravimeter manufacturers.
One of them is Micro–g LaCoste of Colorado. They manufacture the gPhoneX relative gravimeter, (
https://microglacoste.com/product/gphonex-gravimeter/), which is a modern development of the older, purely mechanical LaCoste & Romberg or Worden gravimeters (
https://gpg.geosci.xyz/content/gravity/gravity_data.html) This doesn't directly measure gravitational acceleration, but gives a reading compared to a known gravitational acceleration measurement. The readings are electronic and can be logged on a computer, which is why it "can also be used as an ultra sensitive low frequency seismometer". So that's a gravimeter which can be used as a seismometer.
Then there's their CG-6 Autograv portable survey gravimeter (
https://microglacoste.com/product/cg-6-autograv-gravity-meter/) This has a much wider operating range, but can't be used as a seismometer. The SEA III Marine Gravity System is for use on ships (
https://microglacoste.com/product/sea-iii-marine-gravity-system/) and the TAGS-7 Dynamic Gravity Meter is for aircraft (
https://microglacoste.com/product/tags-7-dynamic-gravity-meter/) and neither of these double as seismometers – it's hard to think how an aircraft-based device could. Interestingly, Micro-g quote the range of variations of g across the world in the SEA III brochure (
https://microglacoste.com/wp-content/uploads/2024/11/SEAIII-Brochure_R13.pdf)
Earth’s gravity varies from 978 to 983 Gals at sea level (full change of 5 Gal)
How do they know that? Because for over 80 years they have been making the instruments that measured it!
Micro–g also build the A10 Portable Absolute Gravity Meter (
https://microglacoste.com/product/a10-outdoor-absolute-gravimeter/) and the FG-5X Absolute Gravity Meter (
https://microglacoste.com/product/fg5-x-absolute-gravimeter/) which both use a dropping mass to measure gravitational acceleration directly. The FG-5X is the standard by which all the rest are judged and by which all the rest are calibrated, but these two are where you have got tangled up with the daft idea these machines monitor the bottom mirror for tiny vibrations to measure gravity.
From the A10 brochure:
The A10 operates by using a free-fall method. An object is dropped inside a vacuum chamber and its position is monitored very accurately using a laser interferometer. In 2004, the BIPM (Bureau International de Poids et Mesures) proclaimed the ballistic freefall method as an official primary method for measuring gravity.
The free-fall trajectory of the dropped object is referenced to a very stable active-spring system called a “Superspring”. The Superspring provides seismic-isolation for the reference optic to improve the noise performance of the A10.
The optical fringes generated in the interferometer provide a very accurate distance measurement system that can be traced to absolute wavelength standards. Very accurate and precise timing of the occurrence of these optical fringes is done using an atomic rubidium clock that is also referenced to absolute standards.
The measurement is directly tied to international standards, and this is what makes the A10 an absolute gravimeter. By basing the measurement on these standards, the system is inherently calibrated and will neither drift nor tare over time. (https://microglacoste.com/wp-content/uploads/2017/03/Brochure-A10.pdf)
The same is true for the FG-5X. The bottom mirror is isolated from vibrations of the meter body by the Superspring mechanism, so gravitational acceleration is being measured by very precise timing of the fall of the top mirror in the vacuum and only by that means.
I think the person who originally came up with Universal Acceleration was trolling you and the wiki has swallowed that troll – hook, line and sinker. You would do well to forget the whole idea, which carries the seeds of its own destruction in the variations in gravitational acceleration across the world, which would tear an upwardly accelerating Earth apart.
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