Nearly three-quarters of the Earth's surface is covered by water, most of it in the seas and oceans. For thousands of years people have been finding ways to cross this water. At first they built rafts, and boats with oars, but around 2900 BC, the Egyptians began to use sails. From then on, sailing ships ruled the seas until a century ago. Today, big ship have engines, but small sailing ships are used for sport, fishing and local trade. Of course sailing ships are reliant in the wind to power them. Sailors are unable to change the direction of the wind, but they can change the direction of their sailing boats by steering a zigzag course, called tacking.
FACT FILE
Yacht racing is a very popular sport these days. In yacht racing it is very often the efficiency with which a boat tacks, compared with its competitors, that makes it a wimner.
resources: Tell me why (Chancellor Press)
image 1: http://www.trinitysailing.org/wp-content/uploads/2012/05/leader.jpg
image 2: http://keyassets.timeincuk.net/inspirewp/live/wp-content/uploads/sites/22/2015/09/RWYR1.jpg