SortStack #71 — 2026-08-19

By speed · Order from slowest to fastest.

1. The growth of human hair 175.3 mm/year

   Scalp hair grows roughly 1.25 centimetres a month, so a single strand reaching your shoulders is years old.

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 housefly in flight 6.8 km/h

   A housefly tastes with its feet, so it can decide whether something is food the moment it lands on it.

4. A galloping zebra 66 km/h

   No two zebras have the same stripe pattern, which may help them recognise each other and confuse biting flies.

5. A running reindeer 80 km/h

   Reindeer eyes change colour with the seasons, turning blue in winter to see better in the dim Arctic light.

6. The winds of a violent tornado 480 km/h

   The strongest tornado winds ever measured can strip bark from trees and drive straw into solid wood.

← All puzzles · Play today’s SortStack