Physics
How does heat affect the Eiffel Tower's height?
Quick fact
The tower's iron expands when heated, causing its height to increase by up to 15 centimeters (6 inches) on a hot day.
Why this is interesting
The Eiffel Tower stands up to 6 inches taller during hot summer days than in the winter cold—it's alive with temperature.
Read the full explanation
Understanding How does heat affect the Eiffel Tower's height?
Iron expands with temperature. When the sun heats the metal, its atoms vibrate more and push apart slightly, increasing the overall length of the structure.
A deeper explanation
Thermal expansion is not uniform: the side facing the sun heats more and expands more, causing the tower to lean slightly away from the sun by up to 7 centimeters (2.8 inches). Gustave Eiffel designed the tower with this in mind, building in expansion joints and using a lattice structure that allows free movement. The phenomenon is so predictable that the tower's height is calculated to the millimeter each day, making it a living thermometer—and a constant reminder that even the most solid landmarks are at the mercy of physics.