Researchers using the Laser Relativity Satellite 2 (LARES-2) have achieved a measurement of frame-dragging with more precision than ever before, confirming Albert Einstein’s general theory of relativity with a margin of error of just one to two parts per thousand based on their statistical models. The mission, led by Ignazio Ciufolini, a physicist at the Sapienza University of Rome, utilized laser-ranged satellites to observe how the Earth’s rotation warps surrounding spacetime. The findings were published Wednesday in Nature (DOI: 10.1038/s41586-026-10715-0).
LARES-2 and the Measurement of Frame-Dragging
Frame-dragging, a phenomenon often compared to a spoon spinning in honey—moving the honey and anything within it as it turns—occurs when a massive, rotating object pulls spacetime and anything in its orbit along with it. While Einstein’s general theory of relativity, which debuted in 1915, posits that gravity is understood as objects falling along the curvature of spacetime, detecting this specific consequence requires extreme precision. The latest study confirms that Einstein’s predictions remain accurate under high-resolution scrutiny.
The experiment relied on LARES-2, a mirror-covered orb launched into orbit by the Italian Space Agency in 2022. The satellite acts as a galactic disco ball, allowing scientists to bounce laser beams off its mirrors to determine its exact orbital position. By combining the measurements of LARES-2 and NASA’s earlier Laser Geodynamics Satellite (LAGEOS) missions, Ciufolini and his team canceled out the gravitational perturbations of the sun and moon to pin down frame-dragging. “We improved by a factor more than 10 the measurement of frame-dragging—and in physics that’s a lot,” says Ciufolini.
Daniel Holz, an astrophysicist at the University of Chicago who was not involved in the study, described the method as “very nice” and “elegant.” He noted that the team treated the entire orbit of the satellite as a gyroscope. Compared to NASA’s $750-million Gravity Probe B mission launched in 2004, which used onboard gyroscopes, Holz stated, This thing is 100 times better, and cost a lot less.
Evaluating Alternative Theories of Gravity
Beyond validating Einstein, the data serves as a filter for competing gravitational theories. Specifically, the findings have placed significant constraints on Chern-Simons theory, one of the leading alternatives emerging from quantum gravity frameworks. While Chern-Simons theory introduces mathematical corrections intended to work at ultra-small scales where quantum mechanics and gravity must coexist, it predicts a different magnitude for frame-dragging than general relativity.
“By measuring frame dragging very precisely, we have been able to put limits on what is predicted by Chern-Simons theory,” said Ciufolini. While the results do not rule out these alternative frameworks entirely, they eliminate a large range of potential variations. Paul Lasky, an astrophysics professor at Monash University who was not involved in the study, noted that the work is a “pristine measurement.” However, he cautioned that it remains limited to weak gravitational fields within our solar system, where departures from general relativity are less likely to appear than in regimes of stronger gravity.
K1 Tide Impacts and Future Scientific Utility
A critical challenge in the experiment was isolating frame-dragging from the gravitational influence of the sun and moon. While most tidal effects were canceled by combining data from LARES-2 and LAGEOS, one lunisolar tide called K1 introduced uncertainty into the equation. The team tracked the impact of the K1 tide on the satellites for three years to refine their orbital models.
This process yielded a “bonus finding” regarding the strength of the K1 tide, which may have terrestrial applications. “My Chinese colleagues tell me that if we improve the knowledge of tides, we can indirectly improve the study of earthquakes,” Ciufolini said. Furthermore, the longevity of these laser-ranged satellites, which can last for hundreds of years, suggests that the accuracy of frame-dragging measurements will continue to increase. “The more you wait, the more data you accumulate, and the better the results of frame dragging measurements will be,” Ciufolini added.
Comparing Mission Costs and Precision
| Mission | Year Launched | Method | Relative Performance |
|---|---|---|---|
| Gravity Probe B | 2004 | Onboard gyroscopes | Lower precision / $750-million |
| LARES-2 | 2022 | Orbit as a gyroscope | 100 times better / Lower cost |
As Holz observed, the research adds “another feather in Einstein’s cap,” affirming the ongoing success of general relativity. While some theories that creative theorists were excited about that might break relativity are ruled out, Holz noted, That’s how progress happens. Now we go onto the next one.
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