Explained: The physics behind Eiffel Tower's growing height in summer

The Eiffel Tower experiences a measurable increase in height during summer due to the thermal expansion of its iron structure. Originally designed to stand 300 meters tall for the 1889 World’s Fair, the tower’s iron lattice expands when heated because atoms in solids vibrate more and push apart as temperature rises. The coefficient of thermal expansion for the tower’s iron is about 12 × 10⁻⁶ per °C, meaning that for every degree Celsius increase, a one-meter iron piece lengthens by roughly 12 micrometers. Given Paris’s temperature swings from below –20 °C in winter to around 40 °C in summer, the tower can theoretically grow by up to 36 centimeters (about 14 inches) at its full height. In practice, engineers observe a seasonal height variation of about 12 to 15 centimeters (5 to 6 inches), which aligns with theoretical predictions once the tower’s complex lattice structure and uneven heating are considered. Additionally, sunlight causes one side