Stefan Gates visits the Royal London Hospital where he learns about measuring and controlling temperature. He reads the story of ‘Goldilocks and the Three Bears’ to a group of children.

A demonstration of how to measure the air temperature using a thermometer. There are temperature differences between day and night, and the temperature varies between shade and full sunshine.

The principle is simple; rather than directly measuring the temperature of the flame, use it to heat up something of known mass and composition and then dunk that object in some water. If you know ...