Thermal Expansion: Why Bridges Have Gaps

Thermal expansion means most materials get bigger when heated and shrink when cooled.
Bridges have small gaps—called expansion joints—to let them safely expand in hot weather.
Without gaps, heated metal or concrete could buckle, crack, or warp the structure.
Train tracks also use this principle—otherwise, summer heat could make rails bend.
Even sidewalks include tiny gaps to prevent cracking from thermal stress.
Metals expand more than stone or concrete, so engineers account for different rates.
Expansion is why lids loosen when run under hot water—the metal cap expands faster.
Airplanes, skyscrapers, and pipelines are all designed with thermal expansion in mind.
The effect may be tiny per degree, but across long distances it adds up.
Thermal expansion shows how invisible temperature changes can shape massive structures.