Читать книгу 1434: The Year a Chinese Fleet Sailed to Italy and Ignited the Renaissance - Gavin Menzies, Gavin Menzies - Страница 16

There are no signposts in the open ocean. The only way a naviga-tor can determine his position is by using the stars, planets, sun, and moon.

As a first step, a navigator must have a system of providing markers across the oceans. This system of markers, adopted by all seafaring civilizations for millennia, is latitude and longitude. It involves drawing imaginary horizontal and vertical lines over the globe. Horizontal lines are called latitude lines, and the vertical are longitude lines.

Latitude lines are parallel with the equator; each longitude line passes through both the North and South Poles. So a navigator’s precise position can be fixed on the globe using a common system.

In order to have produced an accurate map of the world by 1418, the Chinese fleets must have had such a system to determine their positions at sea. Without an accurate system, captains could not have known the true locations of newly discovered lands, and any map derived from their disparate calculations would have been an incoherent mess.

Unlike the Europeans, who followed Babylonian astronomers with 360 degrees of longitude, the Chinese employed 3651⁄4 degrees. The Chinese used latitude degrees below Polaris (at 90° elevation). The Europeans used latitude above the equator (Polaris 0° elevation). The results are the same for both systems.

Diagrams showing the lines of latitude and longitude around a globe.

After establishing a common system for the earth, the Chinese next had to establish a common map of the heavens. Each navigator would have had to use the same name for the same star as well as the same star map from which longitude would have been determined.