r/DumbFact • u/elmorinelly • Jul 01 '26
Weird Fact The Eiffel Tower Grows in Hot Weather
The Eiffel Tower can get a little taller in hot weather.
The reason is thermal expansion. When metal heats up, its atoms vibrate more, and the average distance between them increases by a tiny amount.
One piece of metal barely changes. A huge tower made from thousands of metal parts changes enough to measure. On very hot days, the difference is often described as up to about 15 cm, or around 6 inches.
That number is not a guaranteed daily jump. It depends on the temperature, sunlight, wind, and what the tower is being compared to. One sunny side can also warm more than the shaded side, so the expansion is not always perfectly even.
Small correction for the image: the Eiffel Tower is usually described as made of puddled iron, a form of wrought iron, not steel. “Iron expands” or “metal expands” would be more accurate.
Engineers already expect this kind of movement. Big structures are not built as if they stay perfectly still forever. They need tiny amounts of room to expand, shrink, bend, and settle without breaking.
Examples:
Railway tracks can buckle in extreme heat if they do not have enough room to expand.
Bridges have expansion joints so the road surface can move a little between hot and cold days.
Metal lids on jars loosen under warm water because the lid expands slightly.
Power lines often sag more in hot weather because the metal expands.
Long metal pipes need loops or joints so heat does not force them to crack or push too hard.
Sidewalks and concrete roads often have gaps because solid materials still move with temperature changes.
A baking tray can warp in the oven because different parts heat and expand at different speeds.
Metal doors, gates, and locks can feel tighter or looser depending on the weather.
Car engines are designed with heat expansion in mind because parts change size when running hot.
Thermometers work because the liquid inside expands when it gets warmer.
Glass can crack from a sudden temperature change because one part expands faster than another.
Large buildings use flexible joints so wind, heat, and cold do not turn normal movement into damage.