Empirical Earth · Rotation & How We Measure It

The gyroscope — rigidity, precession, and the spin it can’t hide

The claim

“A gyroscope shows no rotation — its ‘drift’ is just error, proving the Earth is still.”

What is measured

A gyroscope’s spinning rotor holds its axis fixed in space (rigidity, L = Iω) and turns only when torqued (precession, Ω p = τ/Iω). Held against a turning Earth it appears to drift at 15°×sin(latitude) per hour. That is the signal a gyrocompass uses to find true north, and a ring-laser gyro reads directly.

What would show this is wrong

a free, low-friction gyro that shows no apparent drift at any latitude, or a drift that does not follow 15°×sin(latitude) per hour. Neither is observed.

Sources

  1. Gyroscope: rigidity and precession. A spinning rotor conserves angular momentum L = Iω, so its axis resists reorientation (rigidity in space); an applied torque makes the axis precess perpen link
  2. The gyrocompass. A free gyro’s axis stays fixed in inertial space, so as the Earth turns it appears to drift; a gyrocompass adds gravity control that precesses the axis until the drift nulls link
  3. Gyroscopic inertia and gyrocompass design: apparent drift, hemisphere reversal and rotor sense. A free gyro’s spin axis follows the movement of a star across the sky; the apparent drift is c link
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