Empirical Earth · Rotation & How We Measure It

The Earth’s many motions — and why we feel none of them

The claim

“If Earth were spinning and hurtling through space we’d feel it — so it must be motionless.”

What is true

Those speeds are real and they are enormous. A person standing still is moving in several directions at once, very fast.

What is measured

Earth carries us through at least half a dozen simultaneous motions: spin, orbit, galactic orbit, cosmic drift, plus precession, nutation and wobble. Yet we feel none, because steady motion produces no sensation and the rest are free-fall or far too gradual. “We’d feel it” misunderstands how motion works.

What would show this is wrong

any sensation or instrument that reads absolute velocity (none has ever been found, the basis of relativity), or the spin’s equatorial effect being absent (it is measured at ~0.3% of gravity). Both are the opposite of what is observed.

Sources

  1. Axial precession of Earth’s axis. Earth’s rotation axis traces a cone once every ~25,772 years, gradually changing the pole star (Polaris now, Vega in ~12,000 years) and moving the equinoxes link
  2. Nutation and the Chandler wobble. Superimposed on precession, nutation nods the axis with a main 18.6-year period (~9″); the Chandler wobble shifts the point where the axis meets the surface link
  3. The galactic year and the Sun’s galactic speed. The Solar System orbits the center of the Milky Way at ~230 km/s (828,000 km/h; 514,000 mph), completing one galactic year in roughly 225 mill link
  4. The CMB dipole: our motion through the cosmos. The cosmic microwave background is ~0.0034 K warmer in one direction, implying the Solar System moves at ~369 km/s relative to the CMB rest fra link
  5. Milankovitch cycles: obliquity, eccentricity & precession. Earth’s axial tilt varies between ~22.1° and 24.5° (~41,000 yr), its orbital eccentricity cycles over ~100,000 and 413,000 yr, and link
  6. The Moon’s orbital speed. NASA’s Moon fact sheet gives a mean orbital velocity of 1.022 km/s (about 3,680 km/h), ranging from ~0.966 to ~1.100 km/s over its elliptical orbit. NASA NSSDCA: Mo link
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