The Eiffel Tower Grows in Summer

While it may appear as a static and unyielding monument (Review), the Eiffel Tower is in a constant state of subtle motion, breathing with the Parisian seasons. This behavior is not due to a flaw, but rather a fundamental principle of physics at a massive scale. The tower's entire structure, composed of over 18,000 individual pieces of puddled iron, responds directly to changes in ambient temperature. This phenomenon, known as thermal expansion, is a property of most materials.

On a hot summer day, the sun's energy is absorbed by the iron framework. This added energy causes the atoms within the metal to vibrate more vigorously and push further apart, forcing the material to expand in all directions. Across the tower's colossal 300-meter height, this microscopic expansion accumulates, causing the entire structure to stretch upward by as much as 15 centimeters. Interestingly, the side of the tower facing the sun expands more than the side in the shade, causing the monument to lean slightly away from the sun throughout the day.

This effect was no surprise to its visionary engineer, Gustave Eiffel, who designed the tower with this movement in mind. The intricate lattice structure and the rivets holding it together were engineered to allow for this expansion and contraction without putting stress on the iron. As winter's chill returns, the tower contracts back to its standard height, completing its annual cycle of growth and shrinkage.