$$\require{cancel}$$

# 2.21: The Dark Ages

After the 2nd century B.C. the Greek civilization went into decline and was eclipsed by the Roman Empire. Claudius Ptolemy was another scholar at the Alexandrian library. Around 140 A.D., he wrote a 130-volume encyclopedia that synthesized the teachings of Greek scholars. In this work, Ptolemy extended the existing star catalogs to 1022 stars. He described a geocentric model of the Solar System, with the Sun, Moon, and planets all moving around Earth in circular paths. Ptolemy's method of tracking planets, using these assumptions, gave fairly good predictions of the planets' positions. This model was accepted for a thousand years. Improving and correcting Ptolemy's system was a dangerous enterprise that cost some people their lives during the Renaissance.

Representation of Ptolemy. Click here for original source URL

Astronomy and science in general did not advance substantially under the Romans, who were more interested in such practical matters as agriculture, engineering, and governance than they were in studies of nature and the universe. With the fall of Rome in 410 A.D., maintaining the repository of knowledge in Alexandria became more difficult. Remember that this was centuries before printing; many books existed in only a few handwritten copies. Among the last guardians of the library was the first known woman astronomer, Hypatia. Widely admired for her learning and eloquence, she corresponded with leading scholars, wrote a commentary on Ptolemy's work, and invented navigation devices. But during riots that plagued Alexandria's decline, she was murdered by a mob. Over the next century, the library buildings were burned several times, and the best collection of Greek books was lost or scattered.

'"Hypatia" at the Haymarket theatre. Philammon declaring his love for Hypatia'. Print from the first page of?The Graphic, 21 January 1893. Click here for original source URL.

It was a sad point in history. Much general knowledge was lost. The scientific way of looking at the world, gained among the ancient Mediterranean cultures, languished and was forgotten. Only through circuitous and painful routes was some of this knowledge reintroduced centuries later into Europe. During the long Dark Ages that followed, other cultures were the keepers of the flame of astronomy. This period is a sobering reminder that progress and knowledge do not always march forward; they can be derailed by social chaos and unenlightened or brutal governments.

The Great Library of Alexandria, O. Von Corven, 1st century. Click here for original source URL.