Coriolis: The Earth's Spin in Your Ballistic

"The Earth's rotation is too slow to matter - nothing measurable is affected by it."

You can't feel it in a sink (the effect there is ~a billionth of a metre - the basin's shape wins), but you can verify it two ways. (1) Numbers: take a projectile fired north at 1,000 m/s from mid-latitudes (45°), compute the Coriolis deflection, and compare with published firing tables - the US Navy's fire control manual (public domain) includes the term. (2) The big version: watch hurricanes from space - Northern Hemisphere storms spin counter-clockwise, Southern Hemisphere storms clockwise, every single time.

a = 2·v·ω·sin(φ), where ω = 7.29×10⁻⁵ rad/s (the Earth's spin rate) and φ is your latitude. A plane at 600 mph (268 m/s) at 70° N feels 0.037 m/s² - small, not zero. A 100 km artillery shot (100 s flight) deflects ~5-10 m to the right in the Northern Hemisphere. A century of firing tables that ignored this would have missed by metres to tens of metres.

Ascher H. Shapiro (MIT) published 'Bath-Tub Vortex' in Nature (1962): the Coriolis effect is far too weak to determine which way a tub or sink drains - the basin's shape and how you start the water win. The US Navy's fire control manual includes the Coriolis term. Every hurricane's spin direction is a live demonstration.

The Coriolis effect exists only because the ground moves at different speeds at different latitudes - 1,670 km/h at the equator, 0 at the poles. A flat, non-rotating disc has no Coriolis effect at all. It is measured, tabulated, and used in real weapons and weather forecasting.