More than a century after Albert Einstein first transformed our understanding of gravity, his general theory of relativity continues to withstand ever more demanding experimental tests. Now, an international team led by Ignazio Ciufolini at the Chinese Academy of Sciences has carried out the most precise measurement yet of one of the theory's most subtle predictions: the dragging of spacetime caused by Earth's rotation.
Published in Nature, the team's results provide the strongest confirmation to date that Einstein's description of gravity remains accurate even under extraordinarily precise scrutiny.
Gauntlet of tests
Since its publication in 1915, Einstein's theory of general relativity has been subjected to a succession of increasingly stringent experimental challenges. Astronomers and physicists have tested its predictions using everything from eclipses and planetary orbits to atomic clocks, pulsars and gravitational waves. Each new experiment has sought evidence that spacetime behaves differently from Einstein's description, potentially revealing the need for a more complete theory of gravity.
Yet despite increasingly sensitive observations spanning more than a century, relativity has consistently matched experimental results, while alternative theories have struggled to produce convincing evidence for departures from its predictions.
Evidence in frame-dragging
Among the theory's most intriguing predictions is "frame-dragging": the idea that a massive, rotating object doesn't simply curve spacetime but also drags it around as it spins. Although the effect is exceptionally small around Earth, it can be detected by carefully tracking the motion of satellites in orbit.
To achieve the most accurate measurement yet, the researchers combined observations from the Laser Relativity Satellite 2 (LARES-2), launched by the Italian Space Agency in 2022, with data from the earlier LAGEOS satellites and NASA's GRACE mission. LARES-2 was specifically designed for this task, with a dense, spherical structure covered in retroreflectors that allow its position to be measured with extraordinary precision using lasers fired from ground stations.
The satellite's orbit was chosen to minimize the influence of non-gravitational forces, allowing the researchers to isolate the tiny changes caused by Earth's rotating mass. They also accounted for subtle distortions in Earth's gravity field, including the effects of tides raised by the moon and sun, which would otherwise obscure the signal.
Einstein's predictions hold out
After analyzing three years of observations, Ciufolini's team measured Earth's frame-dragging with a relative uncertainty of just one part in a thousand—around an order of magnitude more precise than previous measurements. Crucially, the observed effect matched Einstein's predictions within this exceptionally narrow margin of error.
Beyond providing the most stringent solar system test yet of frame-dragging, the findings further restrict the range of possible alternatives to general relativity. Any competing theory that predicts measurable differences in this effect must now fit within far tighter experimental limits than before.
The researchers also showed that their analysis improves measurements of Earth's lunisolar tides, highlighting how experiments designed to test fundamental physics can also enhance our understanding of the planet itself. More than 100 years after its publication, Einstein's theory has once again emerged from an even tougher test with its predictions intact.
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Publication details
Ignazio Ciufolini et al, LARES-2 satellite measures frame-dragging effect around the Earth, Nature (2026). DOI: 10.1038/s41586-026-10715-0
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Citation: Frame-dragging observations validate Einstein yet again (2026, July 14) retrieved 14 July 2026 from https://phys.org/news/2026-07-validate-einstein.html
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