Bridge gaps
Long bridges need expansion joints because even millimeters per meter can add up over many meters.
Learning Mission
Thermal Expansion Visualizer
Heat a material, cool it down, compare metals, and see why tiny length changes matter in bridges, rails, and everyday objects.
Big idea: Most solids expand when heated and contract when cooled because their particles vibrate more and usually sit a little farther apart.
Choose a material to change its expansion coefficient.
1.00 m
0.5 m25 m50 m
20 C
-20 C50 C120 C
100 C
-20 C140 C300 C
120x
Set to 1x to see why real thermal expansion is often hard to notice.
Try a real-world case
Delta T80 C
Alpha23 x 10^-6 /C
Delta L1.84 mm
Final length1.0018 m
Not to scale: The expanded or contracted gap in the picture is magnified for demonstration only. Use the Delta L readout for the real calculated change.
Heating causes expansionThe material is warmer than the starting temperature, so the final length is slightly larger.
Delta L = alpha x L0 x Delta Talpha is the material's linear expansion coefficient, L0 is original length, and Delta T is the temperature change.
Compare materials at the same temperature change
The same 1 m bar does not expand equally for every material. The coefficient alpha tells us how strongly the material responds to temperature.
What thermal expansion explains
Railway gaps
Rails can buckle if they are heated and have no space to grow.
Hot lids
A metal lid can loosen when warmed because the metal expands slightly.