A Student's Stubborn Question

In 1963, a Tanzanian schoolboy named Erasto Mpemba was making ice cream with his classmates. Everyone else let their mixture cool before putting it in the freezer. Mpemba skipped that step.

When he asked his teacher why, he was told he must be confused. But Mpemba kept asking — eventually convincing a visiting physics professor to test it. The professor confirmed the result, and they published a joint paper in 1969 that reignited a debate stretching back to Aristotle.