Watch as a compass

Hold a watch horizontally, with the hour hand pointing directly to the sun. If you halve the distance between the hour hand and the 12 with a match, the end of the match points directly to the south.

In 24 hours the sun ‘moves’, because of the earth’s rotation, once around the earth. But the hour hand of the watch goes twice round the dial. Therefore before midday we halve the distance from the hour hand to the 12, and after midday from the 12 to the hour hand. The match always points to the south. At midday, at 12 o’clock, the hour hand and the 12 both point to the sun standing in the south.