Flint

strike hard. one spark is never enough.

strike a steel across a flint and shower sparks into a tinder nest until enough land at once to catch

striking steel on flint shaves off flecks of iron hot enough to burn in the air: the faster the steel moves, the more energy turns to heat and the more sparks fly. each cools within a second, so tinder catches only when enough land close together in time.

Concepts: friction, energy, heat, chemistry.

An interactive you play with one thumb, on Wundr.