Key facts
- A satellite called LARES-2 was used to measure Earth's frame-dragging effect.
- The experiment achieved an uncertainty of just 0.2 percent in measuring the Lense-Thirring effect.
- LARES-2's design minimized non-gravitational forces like photon pressure.
- The experiment utilized two satellites, LARES-2 and LAGEOS, in supplementary orbits to cancel out Newtonian perturbations.
- The measurement confirmed Einstein's general theory of relativity and placed limits on alternative theories like Chern-Simons theory.
Scientists have conducted the most precise test to date of Albert Einstein's general theory of relativity, specifically the phenomenon known as frame dragging or the Lense-Thirring effect. This effect predicts that a rotating mass, like the Earth, twists the fabric of space-time around it. Measuring this effect on Earth has been historically challenging due to the planet's relatively small mass and slow rotation compared to celestial bodies like black holes.
The research team, led by physicist Ignazio Ciufolini, utilized the LARES-2 satellite, developed by the Italian Space Agency. This satellite, resembling a disco ball, is a dense sphere designed to minimize non-gravitational forces, such as those from photons. Its low area-to-mass ratio and lack of propulsion or electronics make its motion primarily governed by gravitational fields, acting as a precise 'test particle'.
To achieve unprecedented accuracy, the team employed a dual-satellite strategy. LARES-2 was paired with NASA's LAGEOS satellite, launched in 1976. By using two satellites in supplementary orbits with inclinations summing to 180 degrees, the researchers could cancel out Newtonian perturbations caused by Earth's equatorial bulge. This cancellation allowed the subtle frame-dragging signal to emerge.
Further challenges included accounting for lunisolar tides, gravitational disturbances from the Moon and Sun that modulate Earth's gravitational field. The team collected data over a full 1,050-day precession cycle, enabling them to average out and remove these tidal effects. After meticulous data processing, they measured a steady drift in the satellites' orbits of approximately 61.3 milliarcseconds per year, which is the signature of spacetime twisting.
The measured value closely aligns with Einstein's predictions, with a tiny margin of error of one to two parts per thousand. Beyond confirming general relativity, the study also places significant constraints on alternative theories, such as Chern-Simons theory, by narrowing the range of its predicted frame-dragging magnitudes. As a bonus, the experiment yielded a more precise measurement of the K1 lunisolar tide's strength, offering potential new insights for earth science.