Foot per Hour to Mile per Second

Tectonic plates move at 2–15 cm/year on average — far below even 1 ft/h. However, during episodic "slow-slip events" on faults (a kind of slow-motion earthquake), the fault face can creep at detectable rates closer to mm/day. True ft/h movement would be catastrophic — the San Andreas Fault creeping at 1 ft/h would translate to 2.4 miles/day, far exceeding any measured geological rate.

Metal extrusion (forming rods or tubes by forcing material through a die) often runs at 1–100 ft/h depending on the alloy and die profile. Some ceramic and glass fiber drawing processes operate in this range. Paper mill wet-end press sections can be as slow as 10–50 ft/h during startup. These speeds are slow enough that workers can safely observe and adjust the process manually.

Icebergs drift with ocean currents at roughly 0.5–1 km/day, equivalent to about 55–110 ft/h. Calving glaciers can lurch forward at thousands of ft/h during surge events. The famous 2017 calving of iceberg A-68 from the Larsen C ice shelf happened over a period of days — so its "speed" of separation was only a few ft/h at most.

It depends on the magnitude. 1 ft/h = 24 ft/day = 288 in/day — for something moving a few feet per hour, inches per day becomes a large awkward number. Conversely, for very slow movement (0.01 ft/h = 2.88 in/day), in/day gives a cleaner number. Engineers choose whichever unit gives a value between roughly 1 and 1,000 to minimize leading zeros.

Sea stars (starfish) move at roughly 0.06 m/min, which is about 11.8 ft/h — surprisingly fast. Coral polyps and sea anemones are essentially sessile but can contract at a few mm/min. Some fungi extend their hyphal tips at 1–4 mm/h — about 0.003–0.013 ft/h. Slime molds (Physarum polycephalum), often used in computing research, can advance at up to 4 cm/h (about 1.3 ft/h).

The speed of light in a vacuum is exactly 299,792,458 m/s, which converts to approximately 186,282.397 mi/s. Before the SI system was globalised, US and British scientific texts routinely used this figure. The value 186,000 mi/s appears as a rounded approximation in older textbooks. Today, physicists universally use c = 3 × 10⁸ m/s or the exact SI value.

The solar wind — a stream of charged particles ejected from the Sun's corona — travels at roughly 250–500 mi/s (400–800 km/s) depending on whether it is the slow or fast component. During coronal mass ejections, bursts can exceed 1,200 mi/s (2,000 km/s). At 500 mi/s the solar wind crosses the 93-million-mile Earth–Sun gap in about 2 days, which is why space weather forecasters can give roughly 48 hours' notice before a geomagnetic storm hits.

Yes — several. NASA's Parker Solar Probe reached about 430,000 mph (119 mi/s or 192 km/s) at perihelion, making it the fastest human-made object ever. High-powered railgun projectiles tested by the US Navy reached around 2.5 km/s (1.5 mi/s). Intercontinental ballistic missiles (ICBMs) reach approximately 4 mi/s during their boost phase.

Exactly one second — that's the definition. At 1 mi/s you would cross the Atlantic Ocean (about 3,400 miles) in under an hour, reach the Moon (238,855 miles) in about 2.8 days, and reach the Sun (93 million miles) in roughly 12 days. The speed is conceptually useful for calibrating astronomical distances in imperial terms.

Rarely. The main residual use is in some US military ballistics documents and historical astrophysics references. The International Astronomical Union and NASA primarily use km/s for planetary and solar system speeds, and AU/year or c (fraction of light speed) for interstellar scales. Mi/s survives mostly in popular science writing aimed at American audiences unfamiliar with metric.