What is Linear Thermal Expansion?
Put simply: When things get hot, they get longer.
Notice in the animation above how the "Hot" atoms vibrate more aggressively? To maintain that movement without colliding, they push their neighbors further away (shown by the larger gaps).
Across billions of atoms, these microscopic gaps add up to a measurable change in length.
At the atomic level, heat is just energy. As a material gets warmer, its atoms vibrate more vigorously. This vibration creates "personal space" issues - the atoms push their neighbors slightly further away. Across billions of atoms, these microscopic pushes add up to a noticeable change in length. This is why bridges have "expansion joints" (gaps with teeth) and why power lines sag more on hot summer days.
Understanding the Formula
Engineers use a simple formula to estimate this growth:
ΔL = α · L₀ · ΔT
- ΔL (Delta L): The change in length (how much it grew).
- α (Alpha): The Coefficient of Thermal Expansion. This is a material property that says "how sensitive is this stuff to heat?"
- L₀: The original starting length.
- ΔT (Delta T): The change in temperature (Final - Initial).