Eiffel Tower Grows In Summer

While it appears as a steadfast and rigid monument (Review), the Eiffel Tower is surprisingly dynamic, constantly reacting to the Parisian weather. This behavior is due to a fundamental scientific principle called thermal expansion. The tower's structure is composed of over 18,000 pieces of puddled iron, a material that, like most metals, expands when heated and contracts when cooled. On a hot summer day, the energy from the sun causes the iron atoms to vibrate more vigorously, pushing each other apart and causing the entire 1,063-foot structure to increase in height by as much as six inches.

This expansion isn't perfectly uniform across the tower. The side directly facing the sun heats up more than the side in the shade, causing it to expand more. This imbalance results in the tower leaning slightly, with its peak curving away from the sun as it moves across the sky. This was no surprise to its chief engineer, Gustave Eiffel, who meticulously accounted for the effects of temperature and wind in his original 19th-century designs. As winter arrives and temperatures fall, the process reverses. The iron contracts, and the tower shrinks back to its standard height, completing an annual cycle that makes it seem as though the iconic landmark is subtly breathing with the seasons.