Iron structures like the Eiffel Tower can grow up to six inches taller during the summer months due to the principle of thermal expansion.

A closer look

Iron structures like the Eiffel Tower can grow up to six inches taller during the summer months due to the principle of thermal expansion. When the temperature rises, the kinetic energy of the iron atoms increases, causing them to vibrate more vigorously and push further apart from one another, which inevitably expands the overall volume of the metal. Because the sun generally hits only one side of the tower at a time, the structure actually tilts slightly away from the sun as the heated side expands faster than the shaded side. It is a brilliant demonstration of basic physics, though it is incredibly amusing to imagine a ten thousand ton Parisian landmark dramatically stretching out and leaning away from the sun like an annoyed tourist desperately trying to avoid getting a sunburn in July!