Lense–Thirring effecteffect
Austrian physicists Josef Lense and Hans Thirring in 1918, just three years after the creation of GR, found an exact solution for the weak field of a slowly rotating sphere. They showed that the spacetime metric acquires additional components that cause test bodies to precess. The gravitational field of a rotating object splits into a static part (like that of a Newtonian sphere) and a 'gravitomagnetic' part, producing forces similar to magnetic ones. Thus the concept of gravitomagnetism was born.
How it works
To notice the effect, bodies with enormous angular momentum are needed—neutron stars or black holes. For Earth, its existence was confirmed only in 2011 using the LAGEOS and LARES satellites, tracking tiny orbital shifts.
💡 The Lense–Thirring effect is so tiny that the gyroscopes of Gravity Probe B had to be the most spherical objects ever made by humans, with deviations from a perfect sphere of only 40 atomic layers.
\Omega = \frac{2 G J}{c^2 r^3}
Ω — angular precession frequency, rad/s; G ≈ 6.674×10⁻¹¹ m³/(kg·s²) — gravitational constant; J — angular momentum of the central body, kg·m²/s; c ≈ 3×10⁸ m/s — speed of light; r — distance from the center of the body to the test particle, m