On Friday, a team of astronomers led by Ignazio Ciufolini at the Wuhan Institute of Physics and Mathematics reported the most accurate measurement of Earth's frame dragging effect, validating Einstein's general theory of relativity. Using the LARES-2 satellite, they reduced measurement uncertainty to just 0.2 percent.
Understanding Frame Dragging and Its Significance
The phenomenon known as frame dragging occurs when a rotating mass, like Earth, twists the fabric of spacetime around it. This effect, also referred to as the Lense-Thirring effect, was first modeled in 1918 but has primarily been observed near massive black holes. Measuring this effect on Earth has proven difficult due to the planet's relatively small mass and slow rotation.
The LARES-2 satellite, developed by the Italian Space Agency, played a crucial role in this research. Measuring just over 40 centimeters in diameter and weighing 294.8 kilograms, it features a unique design that minimizes interference from non-gravitational forces.
The Innovative Design of LARES-2
LARES-2 is a solid sphere made of Inconel 718, a dense nickel-chromium alloy, equipped with 303 corner-cube retroreflectors. This design ensures that the satellite's area-to-mass ratio is the lowest of any satellite in medium-Earth orbit, allowing for precise gravitational measurements.
Ciufoini stated, “The idea is that we want to measure gravitation. We have non-gravitational effects like photons impinging on the satellite and pushing it.” The satellite's mass and compact size help minimize the impact of such forces.
Methodology for Precision Measurement
The research team collected about 200,000 laser observations from July 2022 to June 2025 to track LARES-2's position with millimeter accuracy. However, Earth's irregular shape posed significant challenges. The team employed a method using two satellites—LARES-2 and the older LAGEOS satellite—to cancel out Newtonian noise.
- LARES-2 launched in July 2022
- LAGEOS launched in 1976
- Orbital inclinations sum up to 180.01 degrees
By synchronizing the satellites, the researchers could isolate the Lense-Thirring effect from the noise caused by Earth's shape and gravitational influences from the Moon and Sun. After carefully removing tidal signals, they were left with a drift measurement of approximately 61.3 milliarcseconds per year, closely aligning with Einstein's predictions.
This groundbreaking work not only reinforces Einstein's theory but also enhances our understanding of gravitational physics.
🤖 This article was rewritten by Feed and Figures' editorial AI from a report originally published by Ars Technica. Facts and quotes are preserved from the original; the rewrite focuses on clarity and structure. For the unedited original, see the source link below.
