Beats per minute to Degrees per hour

A resting heart at 72 BPM is easy to grasp — you can literally count beats for 15 seconds and multiply by four. The same rate in hertz is 1.2 Hz, which is technically correct but meaningless to a patient or nurse. Medicine adopted BPM centuries before hertz existed, and the unit maps perfectly to what clinicians do at the bedside: count beats against a clock.

Roughly: Grave 20–40, Largo 40–60, Adagio 60–80, Andante 76–108, Moderato 108–120, Allegro 120–156, Vivace 156–176, Presto 168–200, Prestissimo 200+. These are guidelines, not laws — conductors interpret them freely. Beethoven was among the first to specify exact metronome markings, and musicians have argued about whether his metronome was broken ever since.

That range aligns with a comfortable walking or light-jogging cadence, which humans find instinctively satisfying. Neuroscience research shows the brain has a preferred "resonance" tempo around 120 BPM — it feels neither rushed nor dragging. Spotify data confirms that the most-streamed songs cluster between 100 and 130 BPM. Outliers exist (ballads at 60–80, drum-and-bass at 170+), but the sweet spot is remarkably consistent.

Yes. A ruby-throated hummingbird in flight can reach 1,200 BPM — 20 beats per second. At rest it drops to about 250 BPM, and during overnight torpor (a mini-hibernation) it can slow to roughly 50 BPM to conserve energy. By comparison, a blue whale's heart beats as slowly as 2 BPM during a deep dive. The range across the animal kingdom spans nearly three orders of magnitude.

Most wrist-based trackers use photoplethysmography (PPG): green LEDs shine into the skin, and a photodiode measures how much light is absorbed. Blood absorbs more green light during a pulse peak. The device counts peaks per minute to get BPM. Chest straps are more accurate — they detect the heart's electrical signal (like a simplified ECG). Both methods report BPM because that is what runners and doctors expect to see.

The ISS completes one orbit (360°) in about 92 minutes, giving roughly 235°/hr — almost 16 times faster than Earth's rotation. That is why astronauts see 16 sunrises every 24 hours. At an altitude of ~408 km, the station covers about 7.66 km/s of ground track. If you could watch it from a fixed point in space, it would visibly sweep through the sky at a rate where one degree takes only about 15 seconds.

Because even tiny drift accumulates into serious navigation errors over a flight or voyage. A navigation-grade ring-laser gyroscope drifts less than 0.01°/hr; over a 10-hour flight that is only 0.1° of heading error. A cheap MEMS gyro drifting 10°/hr would accumulate 100° of error in the same time — useless for navigation. Expressing drift in °/hr makes the operational impact immediately obvious to a pilot or engineer.

Equatorial telescope mounts have a motorised right-ascension axis aligned with Earth's rotation axis. By driving that axis at exactly 15°/hr (one sidereal rate), the telescope counter-rotates against Earth's spin, keeping a star fixed in the eyepiece. Without this drive, stars would drift out of view in seconds at high magnification. Astrophotographers rely on it for long exposures without star trails.

The Moon's apparent motion has two components. It shares the sky's overall 15°/hr westward motion due to Earth's rotation. But it also orbits Earth, moving about 0.55°/hr eastward relative to the stars (360° ÷ 27.32 days ÷ 24 hr). The net effect: the Moon moves westward across the sky at roughly 14.5°/hr, which is why moonrise occurs about 50 minutes later each day.

A Foucault pendulum's swing plane rotates relative to the floor at 15° × sin(latitude) per hour. At the North Pole (90°) that is the full 15°/hr; at 45° latitude it is about 10.6°/hr; at the equator it is zero. The pendulum always swings in a fixed plane in inertial space — it is the Earth rotating underneath it. The sine factor comes from the fact that only the vertical component of Earth's angular velocity vector projects into the pendulum's swing plane. Paris (48.9°N) sees about 11.3°/hr, which is why Foucault's original 1851 demonstration took most of a day to complete a visible rotation.