Empirical Earth · Rotation & How We Measure It

Foucault's pendulum & the Coriolis effect

The claim

“If Earth spun we’d feel it or be flung off; nothing actually detects rotation.”

What is measured

A Foucault pendulum’s swing turns 15.04° × sin(latitude) per hour, zero at the equator, a full circle at the poles, measuring Earth’s spin indoors.

What would show this is wrong

a pendulum whose precession rate did not follow 15.04°/hr × sin(latitude).

Sources

  1. IERS Conventions. Sidereal rotation period and Earth-orientation parameters. International Earth Rotation and Reference Systems Service. Earth rotation / IERS link
  2. Foucault's pendulum (1851). L. Foucault, Panthéon demonstration; precession rate = Ω·sin(latitude). Standard classical mechanics (Goldstein; APS Physics History). Foucault pendulum link
  3. The Coriolis effect. G.-G. de Coriolis (1835); f = 2Ω sin φ; hemispheric reversal of cyclone rotation. Standard geophysical fluid dynamics (Holton, Dynamic Meteorology ); NOAA. Coriolis effe link
  4. Foucault pendulum — precession ∝ sin(latitude), one sidereal day. The swing plane veers 360°×sin(latitude) per sidereal day (~11.25°/h at Paris, ~32 h per turn); Foucault released the bob fr link
The full entry, with the working →

This is one card from Empirical Earth, a free reference that states each flat-Earth claim at its strongest and then answers it with sourced measurements. Nothing is for sale and there are no advertisements.