Navigation is finding your way from one place to another. Today we might think of that in terms of satnavs, which use satellites to locate where we are. However, possibly the most important navigation was made centuries earlier when people began to leave one continent and seek others using sea routes.

The most famous time when this happened was between the 15th and 17th centuries, which is why this period is known as the Age of Discovery. The Age of Discovery refers to how European countries sailed to other parts of the world, although the Chinese and Arabs had also made major journeys.

The most famous navigator from this age was Christopher Columbus, but others include Sir Walter Raleigh and Ferdinand Magellan.

These people, like all others after them (and including modern satnavs) find their place on the Earth's surface using longitude (notice the spelling: it is not longditude as some people pronounce it) and latitude. The latitude can be found by the angle of the Sun at noon, but longitude is based on time. The early navigators could not accurately find their longitude. That only became possible in the 18th century with very accurate clocks.