Frame dragging now measured to within 0.2 percent.

The Italian Space Agency’s mirror-covered LARES-2 satellite, paired with NASA’s older LAGEOS, let lasers isolate spacetime’s rotational drag from Earth’s uneven shape.

Physicist Ciufolini says the result narrows, without ruling out, the Chern-Simons alternative to general relativity.

Sources: Ars Technica