MargenThe Eiffel Tower isn't always the same height. In the peak of the heat it can grow by up to 15 centimetres, then shrink again in winter. Iron breathes.
It is thermal expansion. When metal heats up, its atoms jostle more and drift slightly apart: the whole material stretches. In an iron structure more than 300 metres tall, that small stretch, multiplied along its entire height, adds up to several extra centimetres.
What's more, the side facing the sun heats up more than the others, so the tower leans slightly away from the heat, as if dodging the light.
We like to think monuments are eternal and motionless. But even iron, in its slow way, is always alive.
Source: The Conversation, "The Eiffel Tower gets bigger every summer – here's why".