What do you think of this fact?
The Eiffel Tower seems like the very picture of stability: 330 meters tall, anchored in Paris since 1889. But it isn’t quite as rigid as it looks. The tower grows in summer and shrinks in winter.
Metal hates temperature swings
Almost every material expands when it heats up and contracts when it cools down. Physicists call this thermal expansion. With metal, the effect is especially easy to spot. That’s why bridges and railroad tracks have small gaps and joints, so they don’t buckle in the heat.
With the Eiffel Tower, the effect adds up over its huge height. According to Purdue University and Lonely Planet, its height varies by up to 15 centimeters between the hottest and coldest days. So in summer it’s a bit taller, and in winter it’s shorter again. Nobody can see that with the naked eye, of course.
The tower leans away from the sun
It’s not just about going up, though. When the sun shines on only one side of the tower, that side expands more than the shady ones. The result: the top tilts away from the sun, by up to 18 centimeters (7 inches), according to Wikipedia.
Wind gets the tower moving too. According to Wikipedia, it sways by up to 9 centimeters in the wind. Sounds scary, but for a tall metal structure that’s totally normal.
A giant made of parts
The tower was built from puddle iron, a type of wrought iron. According to Wikipedia, it’s made of 18,038 individual parts joined by about 2.5 million rivets. The iron structure weighs around 7,300 tonnes.
To keep it from rusting, the tower gets repainted every 7 years, according to Wikipedia. That takes about 60 tons of paint.
So the Eiffel Tower never really stands still. In a way, it breathes with the seasons.