Part IV · Mass, Inertia and Gravity

Gravity Control and Superconductors

Frame-dragging is measured — and Ning Li, Podkletnov and Tajmar are the programmes trying to make it big enough to use.

8 min read·gravitomagnetism · Ning Li · Podkletnov · Tajmar · Gravity Probe B

Superconductors are where people go looking for gravity control, and the instinct is good. A superconductor is the largest piece of coherent quantum matter you can hold in your hand. This chapter teaches three things: the real gravity effect relativity predicts, the programmes trying to amplify it, and what the measurements tell the next experiment to do.

The real effect: gravitomagnetism

Einstein's general relativity, in its weak-field form, says gravity has a "magnetic" side. A spinning mass drags spacetime slightly around with it. The effect is called gravitomagnetism, or frame-dragging. The formal name is gravitoelectromagnetism, GEM. None of this is fringe. It is textbook relativity, and it was measured. NASA's Gravity Probe B published results in 2011. It found Earth's frame-dragging at the size relativity predicts.

A gravitomagnetic field equation (GEM)(11.1)

\nabla \times \mathbf{B}_g \;=\; -\dfrac{16\pi G}{c^2}\,\mathbf{j} \;+\; \dfrac{1}{c^2}\dfrac{\partial \mathbf{E}_g}{\partial t}

What this says

Written this way, gravity looks almost exactly like electromagnetism. Moving mass — the current j — makes a 'gravitomagnetic' field B_g. Moving charge makes a magnetic field the same way. This is real, confirmed physics. The catch is size. The 1/c² makes the field around a lab-scale spinning object tiny. It is about a hundred billion billion times weaker than a useful gravity effect needs. Closing that gap is the whole game. It is why every programme here reaches for coherent quantum matter.

Definitive Gravitomagnetism is real weak-field relativity, and frame-dragging is measured (Gravity Probe B, LAGEOS). It is also minuscule. That number is the yardstick for everything that follows.

A spinning superconducting disc winding up precessing rings of gravitomagnetic field around it. — Frame-dragging, modelled: a spinning mass winds spacetime slightly around with it, drawn as precessing field rings around a rotating disc. The effect is real and measured; making it large is the open problem. (Interactive 3D; degrades to the poster.)

The programmes: amplifying it with coherent matter

In the early 1990s Ning Li and Douglas Torr made a proposal with a mechanism. Inside a superconductor, they argued, the coherent spin of the lattice ions could amplify the gravitomagnetic field to useful levels. They called it "AC gravity."

Around the same time Eugene Podkletnov reported something more direct. Objects hung above a large, spinning YBCO superconductor seemed to lose a little weight. He called it gravitational shielding. He later described an "impulse gravity generator" that fired a force beam, using a high-voltage discharge through a superconductor.

A test mass hanging on a balance above a large spinning YBCO superconductor disc, with claimed weight loss marked. — Podkletnov's reported setup: a test mass suspended over a large rotating superconductor disc — the apparatus this whole thread is built around. (Precise vector schematic.)

What the measurements say

Three independent groups have run the weight-loss experiment. Woods, Helme, Cooke and Caldwell (2001) measured no change. Hathaway, Cleveland and Bao (2003) built a well-instrumented rig and measured no change either. NASA-funded evaluations at Marshall did not confirm an effect. The 1997 Podkletnov preprint was withdrawn; the peer-reviewed footprint is the 1992 Physica C paper.

Those runs are not the end of the thread. They are its specification. They fix the size any real effect has to beat. They also raise the obvious question: what did the different runs do differently? A 2026 stream put a specific answer on the table. Perhaps what matters is how fast the disc is spun up, not the speed it finally reaches. That turns a disagreement between laboratories into a number you can scan.

A signal line trending down into the noise band as controls improve over successive years. — The Tajmar arc: a small early signal that shrank as the shielding and controls improved. The bound it left behind is the number the next experiment has to beat.

The most instructive story is Martin Tajmar's. His 2006–07 experiments reported a small anomalous "gravitomagnetic London moment" around spinning superconductors. It was genuinely exciting. He did the right thing with it and improved his own controls. In better-shielded runs from 2009 to 2011 the signal shrank into the noise, and he published that. That is the field's roadmap, not a retreat. His bound is now the number a real effect has to clear.

Open question: does the spin-up rate set the size of the effect? What to watch next: a run that states its ramp rate in advance, and its predicted weight change, on a shielded balance.

Contested Published measurements of superconductor gravity modification disagree with one another. That is what contested means here: under active test, with the next variable named.

The objection · Woods 2001 / Hathaway 2003 / Tajmar's own later work

“Every careful independent attempt to replicate superconductor gravity modification has come back at or near zero, including the proponent's own better-controlled runs.”

The answer

That is a fair summary of the measurements, and this chapter reports them as they stand. Start with what is certain underneath. Gravitomagnetism is real, and Gravity Probe B watched Earth drag spacetime around by exactly the amount relativity predicts. So the question is never whether the effect exists. It is whether coherent matter can make it big enough to notice. The runs that came back at zero give that question a number to beat, and Tajmar's own shielded bound is the tightest one. Two live variables are now on the table: the rate at which the disc is spun up, and, in the nuclear-spin line, the sample temperature that Stark, Grafe and Tajmar's 2024 test showed can imitate a weight change. Watch for a run that states its ramp rate and predicted effect size in advance. That is the experiment this chapter is waiting for.

What the field added — July to September 2026

Three gravity-control threads came back. One new result joined the chapter from an unexpected direction.

Mark Sokol presented Frederick Alzofon's 1981 idea. Polarise the nuclear spins in a sample, Alzofon said, and its weight should change. Sokol described his lab's work on it. The idea now has a modern test on record. Stark, Grafe and Tajmar ran it in 2024 with an NMR machine. They found that temperature is the thing the next experiment must control. A stream proposed a new variable for the spinning-superconductor effect: how fast the spin is ramped up, not the final speed. That turns a dispute between labs into a number to scan. Archival interviews with McDonnell Douglas engineers Robert Wood and Paul Czysz added a real 1968 memo proposing gravity experiments. A major aerospace company funded this line of thought sixty years ago.

The new result is the NbSe₂ cavity paper in Chapter 2. Reshape the vacuum around a superconductor and its critical temperature rises. That is a different quantity than weight. But it is the same family of physics this chapter is about, and it is peer-reviewed. Laithwaite's 1974 spinning-disk lift made a good classroom demonstration of how gyroscopes behave. Research log. Phase and coherence — the thread joining the London moment, flux quantisation and the junction arrays — have their own course: quantum phase and coherence. For the junction physics itself — the two Josephson relations, SQUIDs, qubits and junction arrays — take the Josephson-junction drill-down course.

Where each claim stands

Gravitomagnetism is real weak-field relativity; frame-dragging is measured. Definitive
Coherent quantum matter can amplify it to useful levels (Li–Torr "AC gravity"). Speculative
Podkletnov's weight-loss effect is real. Contested (measurements disagree; under active test).
Tajmar's early London-moment signal was a new effect. Contested (his own shielded runs set the current bound).
Polarising nuclear spins changes a sample's weight (Alzofon). Speculative
What would settle it: a spin-up run that states its ramp rate and predicted weight change in advance. For the nuclear-spin line, an Alzofon-style test with temperature controlled that still shows a shift.

Sources

Primary - the programmes

N. Li & D. Torr (1991), "Effects of a gravitomagnetic field on pure superconductors," Phys. Rev. D 43, 457; (1992) Phys. Rev. B 46, 5489 - the amplification proposal.
E. Podkletnov & R. Nieminen (1992), "A possibility of gravitational force shielding by bulk YBa2Cu3O7-x superconductor," Physica C 203, 441 - the peer-reviewed origin (the later 1997 preprint was withdrawn).
E. Podkletnov & G. Modanese (2001), "Impulse gravity generator...," arXiv:physics/0011026 / physics/0209051. (Downloaded.)

Real gravitomagnetism - the yardstick (beyond the source corpus)

B. Mashhoon (2003), "Gravitoelectromagnetism: a brief review," arXiv:gr-qc/0311030 - GEM is real weak-field relativity; the lab-scale field is ~1e-20 of the claimed effects.
C. Everitt et al. (2011), "Gravity Probe B: Final Results...," Phys. Rev. Lett. 106, 221101 - measured frame-dragging at its tiny predicted size.

Where the physics is worked out

M. Tajmar et al. (2006-2011): gr-qc/0603033, arXiv:0707.3806 - an early signal, then the proponent's own better-controlled runs setting the tightest published bound on it. (Downloaded.)
Independent Podkletnov runs: Woods, Helme, Cooke & Caldwell (2001), AIAA 2001-3363; Hathaway, Cleveland & Bao (2003), Physica C 385, 488 - no weight change measured. These fix the size a real effect must beat.

Where the replication stands: the positive reports are a thin cluster, and the best-instrumented runs measured nothing. The 2026 threads answer with a variable nobody scanned - the spin-up rate - which is what makes a disputed effect testable again.