Which phenomenon causes the Eiffel Tower to become 15 centimeters (5.9 in) taller in the summer?

The Eiffel Tower is a wrought-iron lattice tower on the Champ de Mars in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed and built the tower. The tower is 324 meters (1,063 ft.) tall, about the same height as an 81-storey building.

When temperatures rise, the Tower increases in size! This is a natural physical phenomenon called thermal expansion. Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature. Heat causes an increase in volume that makes the Eiffel Tower a few centimeters taller. This expansion also causes the Tower to tilt slightly away from the sun. When cold winter weather arrives, the metal structure contracts and it can lose a few centimeters as well! The approximate change in height during the winter thru summer seasons of the Eiffel Tower is 15 centimeters (5.9 in).