SortStack #470 — 2027-09-22

By speed · Order from slowest to fastest.

1. The growth of a cave stalactite 0.1 mm/year

   Most stalactites lengthen by less than a tenth of a millimetre a year, dripping mineral by mineral over millennia.

2. A person walking 5 km/h

   The average person takes around 7,000 steps a day, walking the equivalent of several times around Earth in a lifetime.

3. A charging black rhinoceros 54 km/h

   A rhino's horn is made of keratin, the same material as your hair and nails, not bone.

4. A record tennis serve 270 km/h

   The fastest serves leave the racket so quickly the returner must react before the ball has even crossed the net.

5. A Bugatti Chiron at top speed 510 km/h

   The Chiron is electronically limited; unleashed, its tyres would tear themselves apart from the sheer forces.

6. A 5.56mm rifle bullet 3.1K km/h

   Small, fast rifle rounds tumble on impact, transferring energy in ways a slower, heavier bullet would not.

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