SortStack #300 — 2027-04-05

By size · Order from shortest to longest.

1. A tennis ball 6.7 cm

   Tennis balls are pressurised with gas and slowly go flat, which is why fresh cans hiss when opened.

2. A red kangaroo (standing) 1.5 m

   Kangaroos cannot walk backwards, a trait so iconic it earned them a spot on Australia's coat of arms.

3. The Empire State Building 443 m

   It was built in just 410 days during the Great Depression, rising about a floor a day at peak speed.

4. The Brooklyn Bridge (total length) 1.8 km

   When it opened in 1883, a stampede fearing collapse killed twelve people; a circus later marched elephants across to prove its strength.

5. The Channel Tunnel 50.5 km

   Trains run through three parallel tubes beneath the seabed, with a smaller service tunnel between them for safety.

6. The Kiel Canal, Germany 98 km

   The world's busiest artificial waterway, it lets ships skip the long, stormy voyage around Denmark.

← All puzzles · Play today’s SortStack