A spinning gyroscope and a Tesla coil look like props from different centuries, but put one inside the other’s field and you expose the same physics from two directions: energy locked into a conserved oscillation, fighting to stay that way. The coil is a dual-resonant air-core transformer. A spark gap dumps a charged primary capacitor into a few-turn primary, ringing at the LC frequency f = 1/(2π√(LC)). The tall secondary is tuned to match, so energy sloshes back and forth and the secondary voltage climbs by roughly the loaded Q factor, Q ≈ (1/R)√(L/C). Hundreds of volts in become hundreds of kilovolts out, terminated in streamers that are the air itself breaking down. Bring a conductive gyro rotor into that field and three things happen at once: - The oscillating magnetic flux drives eddy currents in the rotor. They dissipate as I²R heating whether or not the rotor spins. - Net braking torque only appears if the field is spatially asymmetric across the disc; a perfectly uniform fie...