Astronomical Talents

In the seventh century, or perhaps even earlier, Chinese scholars and artists produced a map of the night sky. It is an astonishing document, written on paper (a Chinese invention, of course), that correctly pictures more than 1,500 stars, many of which are very difficult to see with the naked eye. According to a report in the London ”Independent”, the Chinese map is

”… several centuries older than the first star maps produced in Europe during the height of the Renaissance when astronomy benefited from the invention of the telescope…

“Two French academics now believe the star chart … may have been drawn as early as the start of the Tang period, AD618. Jean-Marc Bonnet-Bidaud of the French Atomic Energy Agency and Françoise Praderie of the Observatoire de Paris also believe that the Dunhuang manuscript is a copy of a much older map that has since been lost to antiquity. In a description for the British Library's exhibition on the Silk Road, which opens on Friday, the scientists say: "The overall quality of the document clearly demonstrates a mature technique so the chart was probably produced as a copy of an earlier existing document." M. Bonnet-Bidaud said: "Curiously, the information in the texts accompanying the charts is extremely similar in style and content to the notations given in [a] much earlier astronomical text, the Yue Ling or 'Monthly Ordinances', dated approximately 300BC. "This is a direct indication that the charts are based on traditional texts and that they are possibly a reproduction of a much earlier version."

The astronomical knowledge indicated is just one of the marvels of the map.

”One of the technical problems of producing a complete star chart of the sky is the difficulty of converting the three-dimensional sphere of space into a two-dimensional plan, M. Bonnet-Bidaud said. "A freehand drawing based on direct vision will be highly distorted since the eyes see only a limited portion of the sky at a time," he said.

One possibility is that the early Chinese astronomers used a method of projecting the sky onto a cylinder using a Mercator-like projection system - the traditional way of making a two-dimensional map of the spherical Earth by sacrificing accuracy at the poles for the sake of accuracy nearer the equator. Mme Praderie said it is likely that the stars nearer to the poles were drawn separately to overcome the distortions that would otherwise be introduced using such a projection method. "The composition of the chart and its presentation are modern," she said. "They are similar to our modern geographical maps of the Earth."

We should not be so arrogant of our current skills, for they are based on thousands of years of knowledge.