Gyroscope (Mechanical, Optical & MEMS)

Inertial orientation and angular-velocity sensor based on angular momentum conservation, Sagnac interferometry, or Coriolis vibration.

Specifications & Metrics

type: Control & Sensing Mechanism
governing equation: τ = dL / dt = Ω_precession × (I ω_spin) (mechanical); Δφ = 8πAΩ / (λc) (Sagnac optical)
primary function: Inertial attitude reference, gyrocompass true-north seeking, and angular rate measurement
key parameters: Angular momentum (L = Iω), bias stability (°/hr), angle random walk, Sagnac scale factor
originator: Johann Bohnenberger (1817), Léon Foucault (named 1852), Hermann Anschütz-Kaempfe (1904 gyrocompass)

Invented as a gimbaled spinning sphere by Johann Bohnenberger in 1817 and named 'gyroscope' by Léon Foucault in 1852 when he used a spinning rotor to visually demonstrate Earth's rotation, mechanical gyroscopes exhibit rigidity in space and precess at right angles to applied torque.
Modern aviation and submarine inertial navigation systems replace spinning wheels with solid-state Ring Laser Gyroscopes (RLGs) and Fiber Optic Gyroscopes (FOGs) that measure the Sagnac phase shift between counter-propagating light beams, while smartphones use microchip Coriolis vibratory MEMS gyroscopes.
The most precise gyroscopes ever flown — the four superconducting niobium-coated fused-quartz spheres aboard NASA's Gravity Probe B — used London-moment magnetic readout via SQUIDs to measure relativistic frame-dragging to better than 0.5 milliarcseconds per year.