Everyday Thermal Expansion: Why It Matters “Heat expands, cold contracts — ignore this, and things break.” Like massive industrial machines, everyday structures must handle thermal expansion as temperatures rise and fall. Bridges use expansion joints so steel and concrete can expand in the sun and shrink at night — without cracking. Buildings and houses rely on flexible materials and hidden gaps to stop walls from splitting when seasons change. Railroad tracks are laid with tiny gaps between sections — no gaps means buckled, warped rails in summer heat. Understanding thermal growth in these simple examples shows why precision machinery must account for it too. | Ignore thermal expansion in machines, and parts drift out of alignment.