Measurement of Gravitomagnetic and Acceleration Fields around Rotating Superconductors
Martin Tajmar · Florin Plesescu · Bernhard Seifert · Klaus Marhold
Abstract and summary · read the original at the source
In one page
This is Martin Tajmar’s progress report on the hardest measurement in chapter 11. His group at ARC Seibersdorf spun a niobium ring in liquid helium and asked whether a superconductor drags spacetime the way a spinning mass does, only enormously harder. Two things make this paper the one to read rather than the 2006 first announcement. First, the sensors were rearranged into what Tajmar, Florin Plesescu, Bernhard Seifert and Klaus Marhold call a curl configuration, in which every accelerometer has a mirror partner and the pair’s difference cancels tilts, torques and vibration offsets. That raised the signal-to-noise ratio to about 15 to 1 and, importantly, it corrected their own earlier number downward — the single-sensor peaks had been over-read. Second, they added laser gyroscopes, which respond to rotation rate rather than to acceleration and are almost immune to vibration. Both instruments tracked the Cooper-pair density; a reference sensor on the same frame saw nothing.
Why it matters hereChapter 11 asks whether coherent quantum matter can amplify frame dragging into something you could use, and this is the most carefully instrumented attempt to catch it, by the group that made the claim. It belongs to chapter 1 just as strongly, as a worked example of how the evidence ladder is supposed to run: the authors publish their error budget, correct their own earlier figure downward when a better configuration disagrees with it, and end by asking other laboratories to try. That is where the question still sits — the effect has not been established at this size by an independent group, and the two follow-up runs on record are R. D. Graham, R. Hurst, R. Thirkettle, C. H. Rowe and P. Butler’s search in a lead superconductor, Physica C 468, 383 (2008), and Tajmar’s own higher-resolution niobium, liquid-helium and superfluid-helium evaluation, Superconductor Science and Technology 24, 125011 (2011). The 2022 Torino review at /library/stm-c909553daa sets the whole programme in context.
What it claims
01Linearising Einstein’s equations with a non-zero cosmological constant gives Proca-like equations for a massive spin-1 graviton, and if the graviton mass depends on the local density of matter — the condition for the dark energy density measured by WMAP to be constant across the universe — then the cosmological constant becomes something testable on a laboratory bench rather than only across the sky.Introduction, opening paragraphs
What to watch02A rotating superconductor should carry a gravitomagnetic London moment measurable outside the material, equal to twice the angular velocity scaled by the ratio of Cooper-pair mass density to bulk density — for niobium about 3.9 times ten to the minus sixth multiplied by the angular velocity at zero kelvin — and angularly accelerating the ring should induce an azimuthal gravitational field opposing its cause, a gravitational Lenz law.Introduction, Equations 1 and 2
What to watch03In the curl configuration, where each tangential accelerometer is differenced against its mirror partner so that only a closed-loop field survives, a niobium ring gave an in-ring coupling factor of minus 2.26 plus or minus 0.3 times ten to the minus eighth in units of Earth gravity per radian per second squared while superconducting, against minus 1.24 plus or minus 1 times ten to the minus ninth while normal conducting, with a signal-to-noise ratio of about 15 to 1.Accelerometer Measurements, Curl Sensor Configuration, Figure 8
What to watch04Signal-averaging more than 100 profiles in one-kelvin intervals gives an in-ring coupling factor extrapolated to zero kelvin of minus 14.4 plus or minus 2.8 times ten to the minus ninth, following the temperature dependence of the Cooper-pair density prediction multiplied by two — and this figure corrects the group’s earlier single-sensor numbers, which over-predicted the effect because the accelerometer’s tilting plates oscillate and exaggerated the peaks.Accelerometer Measurements, Figure 9 and the paragraph following it
What to watch05Preliminary laser-gyroscope runs, which respond to angular velocity rather than acceleration and are insensitive to vibration, showed an above-ring signal tracking the Cooper-pair density and dropping exactly when the ring crossed its critical temperature, while a reference gyroscope on the same mechanical structure showed nothing within a noise level of 3 times ten to the minus fifth radians per second — which rules out a mechanical torque on the sensor chamber as the cause.Gyroscope Measurements, Figure 11
What to watch06The authors work through each alternative cause in turn — mechanical drag through the helium gas, magnetic offsets, which would need at least 100 millitesla against a measured field change below 1 microtesla, and acoustic noise from boiling helium, which does not reverse with the sense of rotation while the observed effect does — conclude that the gravitomagnetic London moment is the most probable explanation, fitting their prediction within a factor of two, and state the settling condition themselves: the result must be investigated and verified in other laboratories, with different sensors, before any facility-induced effect can be ruled out.Discussion and Conclusion of Results
What to watch
Read it · abstract
Abstract
It is well known that a rotating superconductor produces a magnetic field proportional to its angular velocity. The authors conjectured earlier, that in addition to this so-called London moment, also a large gravitomagnetic field should appear to explain an apparent mass increase of Niobium Cooper-pairs. A similar field is predicted from Einstein’s general relativity theory and the presently observed amount of dark energy in the universe. An experimental facility was designed and built to measure small acceleration fields as well as gravitomagnetic fields in the vicinity of a fast rotating and accelerating superconductor in order to detect this so-called gravitomagnetic London moment. This paper summarizes the efforts and results that have been obtained so far. Measurements with Niobium superconductors indeed show first signs which appear to be within a factor of 2 of our theoretical prediction. Possible error sources as well as the experimental difficulties are reviewed and discussed. If the gravitomagnetic London moment indeed exists, acceleration fields could be produced in a laboratory environment.
The way in
https://doi.org/10.1063/1.2437552Presented at the Space Technology and Applications International Forum, STAIF-2007, and published in AIP Conference Proceedings 880 by Martin Tajmar’s Space Propulsion group at ARC Seibersdorf research in Austria. The manuscript is free to read on arXiv as gr-qc/0610015, but that posting carries arXiv’s assumed legacy licence rather than a Creative Commons licence, so this page holds the summary, the claims and the authors’ own abstract and sends the reader to the source. This is the successor to the group’s 2006 report, which has its own sheet at /library/stm-21102decd7 — read that one for the Cooper-pair mass anomaly this programme set out to explain, and this one for the curl configuration, the corrected coupling factor and the first laser-gyroscope runs.
How to cite it
Martin Tajmar, Florin Plesescu, Bernhard Seifert, Klaus Marhold (2007) Measurement of Gravitomagnetic and Acceleration Fields around Rotating Superconductors. doi:10.1063/1.2437552
Where it sits in the curriculum
Gravity control and superconductorsThe evidence ladderInertia and gravity from the vacuum