SortStack #2087 — 2032-02-25

By speed · Order from slowest to fastest.

1. The creep of a mountain glacier 175320 mm/year

   Glaciers flow downhill under their own weight like very slow rivers of ice, grinding valleys as they go.

2. A falling raindrop 34 km/h

   Raindrops are not teardrop-shaped; they flatten into tiny hamburger buns as they fall through the air.

3. A polar bear running 40 km/h

   A polar bear's skin is actually black under its clear, hollow fur, helping it soak up the Arctic sun.

4. A racing greyhound 76 km/h

   Greyhounds reach their top speed in just a few strides and spend much of a sprint completely airborne.

5. 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.

6. NASA's Parker Solar Probe 692K km/h

   The fastest human-made object ever, it slingshots around the Sun, dipping into the star's blazing outer atmosphere.

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