Ancient Star Maps Gave Rise to Modern Astronomy

September 27, 2017

Scientists have incredibly advanced tools to look at the stars today, but in the era before light pollution, star-gazing was much easier and simpler for the average person—just step outside at night. Pretty early on, and in a variety of cultures, people realized that they could chart the stars and their movements for navigation. The Greek constellations, which were tied to their myths, illustrate how this information moved through time. But humanity’s early star maps are much more than ancient artifacts—they became part of our history and culture, and continue to inform modern science to a surprising degree.

The first complete star map that still exists today was made in 650 A.D. in Dunhuang, western China, a city on the Silk Road. There, a star atlas was meticulously drawn onto a piece of paper, then filed away with other documents in a temple alcove. The space was sealed off at some point, and wasn’t re-discovered until 1907, when a Taoist monk, the self-appointed guardian of the temple, accidentally crashed through a wall to find the hidden cache, which contained sculptures, piles of documents, and the now-famous star map.

“[The map] was most likely made by someone highly educated like a scholar or a court astronomer,” cosmologist Dr. Khee-Gan Lee, a NASA Hubble Fellow at the Lawrence Berkeley National Lab, tells Gizmodo. “This was definitely not amateur work, but was professional for the time.”

Lee is an expert on ancient star maps who has given several presentations on them at U.C. Berkeley over the past few months. The history of star maps matters to him personally, because even today, maps of the cosmos help guide his research.

“Mapping out what we can observe…is one way of inferring some of the fundamental parameters of the universe,” Lee said. A good example of how this works is the recent Dark Energy Survey, which used information about the shapes and distribution of galaxies to “infer the density of gravitational matter in the Universe—one of the fundamental parameters of the Universe,” Lee said. That Survey’s results were also a test of Einstein’s theory of general relativity.

Following the Dunhuang map, there wasn’t another more complete star map for hundreds of years (at least, none that have been discovered yet). All civilizations were limited by technology—they could record what was observed by the naked eye, like the brightest stars and planets. For almost a thousand years, that limitation halted a further understanding of the cosmos. To get more detailed information, humans needed a better eye.

When the first telescopes were developed in The Netherlands in the early 1600s, amateurs and experts alike were excited to try them, even though they only had weak magnifications of 3X or 4X. From Galileo’s early models, to Newton’s, to the 1500-foot-long model designed by Johannes Hevelius, astronomers of the 16th and 17th centuries were limited by the quality of the glass needed to make more powerful telescopes. Not much more could be learned about the stars until higher magnifications were achieved.

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