Empirical Earth · Rotation & How We Measure It
Why we don’t feel the spin (and the oceans don’t fly off)
The claim
“If Earth spun at 1,000 mph we’d feel it, and the oceans would fly off.”
What is measured
Earth’s surface moves at a steady ~1,670 km/h, and steady motion is never felt. Only change is. The leftover spin acceleration is ~0.034 m/s², below the ~0.06–0.1 m/s² the inner ear can detect, while gravity outpulls the spin ~289:1. You’d need to spin ~17× faster (an 84-minute day) to throw the oceans off.
What would show this is wrong
a steady, unchanging linear motion that the human vestibular system can detect with no change in speed or direction.
Sources
- Vestibular linear-acceleration thresholds. Healthy subjects detect the direction of whole-body linear acceleration only above a median ~6.5–8.5 cm/s² (~0.065–0.085 m/s²); the velocity of ste link
- Peak ground acceleration & felt intensity. Felt earthquakes span roughly a few %g up to ~0.25 g at Modified Mercalli VIII (Japan’s Shindo 7 exceeds 0.41 g) — abrupt, oscillating acceleration link
- Earth’s equatorial bulge. Rotation makes Earth an oblate spheroid: the equatorial radius (~6,378 km) exceeds the polar (~6,357 km) by about 21 km, ~0.3% flattening, mapped precisely by satel link
- The vestibular system. The inner ear’s semicircular canals detect angular acceleration; the otolith organs (utricle and saccule) detect linear acceleration and the direction of gravity. Brit link
- Vestibular perceptual thresholds. Measured human thresholds for self-motion: rotation about the vertical near 0.7°/s and linear acceleration on the order of 0.02–0.3 m/s². Human vestibular p link
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