Millihertz to Degrees per second

After a magnitude-9 earthquake the entire planet vibrates like a struck gong, with its deepest mode at about 0.3 mHz — one oscillation every 54 minutes. The surface rises and falls by fractions of a millimeter. You cannot hear it (human hearing starts at 20 Hz), but gravimeters and seismometers worldwide pick it up. The 2004 Sumatra quake kept Earth ringing measurably for weeks.

Ocean swells, tidal constituents, and seiches (standing waves in harbours or lakes) all oscillate in the millihertz band. A 10-second ocean swell is 100 mHz; a harbour seiche with a 10-minute period is about 1.7 mHz. Monitoring these frequencies helps coastal engineers predict resonance in ports and design breakwaters that don't amplify destructive wave energy.

Not directly — our senses are far too fast. But some physiological rhythms operate here: the Mayer wave, a ~0.1 Hz oscillation in blood pressure, sits at the high end of the millihertz scale, and slower vasomotion (tiny blood vessel contractions) can dip below 10 mHz. You don't feel them as vibrations, but they show up clearly on a continuous blood-pressure monitor.

Infrasound is sound below the ~20 Hz threshold of human hearing. The lowest infrasound blends into the millihertz range — the International Monitoring System for nuclear-test detection listens down to about 20 mHz. Sources include volcanic eruptions, meteor airbursts, severe storms, and ocean microbaroms (standing pressure waves between ocean swells and the atmosphere).

Instruments record a time series (pressure, acceleration, displacement) over hours or days, then apply a Fourier transform to extract frequency content. Superconducting gravimeters can resolve Earth's free oscillations below 1 mHz by measuring gravity changes of 10⁻¹² g. The trick is not a fast sensor but a patient, ultra-stable one and enough data to separate signal from drift.

Because °/s maps intuitively to human motion. Tilting your phone 90° in half a second means 180°/s — you can visualise that immediately. The same rate in rad/s (π ≈ 3.14) requires mental conversion. Consumer IMU datasheets list full-scale range in °/s (±250, ±500, ±2000°/s) because the target audience — app developers and game designers — thinks in degrees, not radians.

A standard-rate turn in aviation is 3°/s (completing 360° in two minutes), used for instrument approaches. A fighter jet in a hard combat turn can sustain 15–25°/s, and instantaneous snap rates during aggressive maneuvers can exceed 60°/s. At 20°/s in a tight bank, the pilot experiences 4–6 g of centripetal acceleration, which is near the limit of what a g-suit can compensate for.

A basketball spinning on a fingertip typically rotates at about 3–5 revolutions per second, which is 1,080–1,800°/s. The Harlem Globetrotters can push past 2,000°/s for brief showpiece spins. A professional bowler's ball rotates at roughly 300–500 RPM off the hand, which translates to about 1,800–3,000°/s. Spin rate matters for curve, grip, and the physics of the bounce.

PTZ (pan-tilt-zoom) camera specs list maximum pan speed in °/s — typically 80–400°/s for preset movement and 0.1–5°/s for manual tracking. A camera that pans at 400°/s can whip from one side to the other in under a second, useful for switching between preset positions. The slower manual range lets an operator smoothly follow a walking person without jerky motion.

A standard-rate turn (Rate One) is defined as 3°/s, completing a full 360° circle in exactly two minutes. Air traffic controllers rely on this predictable rate to space aircraft in holding patterns and instrument approaches. The turn coordinator instrument in the cockpit marks the standard rate with reference lines. Faster rates exist (Rate Two is 6°/s), but standard rate keeps the bank angle comfortable at typical airspeeds.