ELI5; why do cars make little tinking noises right after you turn them off and get out?
In: 5
As per the other answers, the metal shrinks as it cools. The other answers haven’t explained how you get a tick sound as a result of that.
Internally, metals have a lattice structure. When a metal is cooling and contracting this sets up some tension in the structure where a layer (and all the layers above it) want to move but they can’t because they’re held in place in the lattice.
After a while the forces build up to the point that the “moving” forces overcome the “staying still” forces and part of the lattice shifts relative to the rest. That sudden movement and stopping is what generates the tick sound.
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