The Eiffel Tower becomes 15 centimeters taller in the summer, due to which phenomenon?
And the answer: thermal expansion.
Standing at 324 meters tall, the exact height of the Eiffel Tower can change depending on the season. When the hot summer sun beats down on it, thermal expansion causes the metal to expand. But once the sun sets, the temperature decreases and the metal contracts.
When an object is heated, its particles gain kinetic energy, consequently moving faster until they take up more space. Most large metal structures (such as the Eiffel Tower) are constructed with this principle in mind, so they can expand and contract a little without breaking.
Changes in temperature work the opposite way too – in the cold winter months, metal can contract and shrink finitely. When it heats back up again in structures like train tracks, warping and disfiguration can occur. In fact, this phenomenon resulted in 190 train derailments during 1998–2002 in the United States alone.
Thermal expansion can also occur in glass structures. Glass is a poor conductor of heat, so when hot water expands only a part of a glass material, it bends until it breaks, either cracking completely or forming fissures across its surface.
To learn more about the laws of thermal expansion, check out the video below.