Does the Eiffel Tower Grow Taller in Summer?

The Eiffel Tower is about 15 centimetres taller in summer than in winter. On a scorching Paris afternoon, the 330-metre iron lattice literally grows; when winter cold returns, it shrinks back down. The tower breathes with the seasons.

Thermal expansion, at monumental scale

All materials expand when heated — their atoms vibrate more energetically and take up slightly more space. For most objects the change is invisible, but scale it up to 330 metres of iron and a 40°C seasonal temperature swing, and the maths becomes dramatic: roughly 15 cm of growth.

Engineers call this thermal expansion, and it is one of the first things they design around. Railway tracks have expansion gaps, bridges sit on flexible bearings, and the Eiffel Tower simply sways and stretches with the weather.

It also leans away from the Sun

There is a bonus effect: on sunny days, the side of the tower facing the Sun heats and expands more than the shaded side, making the whole structure lean slightly away from the Sun — by up to about 18 cm at the top. Gustave Eiffel's engineers understood this perfectly well in 1889.

A 19th-century physics lesson

The tower was built as the entrance arch to the 1889 World's Fair, and at the time it was the tallest human-made structure on Earth. More than 130 years later, it remains a working demonstration of basic physics: heat something up, and it grows. Even icons of Paris obey the laws of thermodynamics.