Here’s one: the Eiffel Tower gets taller in summer.
Because it’s made of wrought iron, it expands when heated by the sun. On hot days, it can grow by up to about 15 cm (6 inches) taller. When it cools in winter, it shrinks back down.
Octopuses don’t just have arms—they have eight arms and three hearts.
Two hearts pump blood through the gills, while the third pumps it to the rest of the body. Even stranger: when an octopus swims, the main heart temporarily stops beating, which is one reason octopuses prefer crawling over swimming—it’s less exhausting.
Octopuses have three hearts, and two of them stop beating when they swim.
The main heart pumps blood through the body, while the other two pump blood through the gills. When an octopus swims, those auxiliary hearts pause, which is one reason octopuses often prefer crawling—it’s much less tiring.
Also, their blood is blue, because it uses a copper-based oxygen carrier called hemocyanin instead of iron-based hemoglobin.