On the course of the stars and the going of clocks. Astronomy and precision horology in Germany around 1800

• Applicants: Dr. Sibylle Gluch; Dr. Peter Plaßmeyer
• Subject Area: History of Science
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 392130775

This project examines the development of the concept of the precision clock. For this reason, it analyzes the usage of clocks in 18th -century astronomy and assesses the influence that clocks asserted on astronomical activities and on the quality of the results attained with their help.In the wake of Isaac Newtons works and due to increasingly pressing practical problems such as navigation at sea, scholars and sovereigns paid intense attention to astronomy from the late 17th century onwards. Towards the end of the 18th century, somewhat later than in England in France, this development became visible in the German-speaking realm with the foundation of numerous observatories. All observatories need precise clocks, because within astronomy just about everything depends on the correct going of the clocks (Berliner Astronomisches Jahrbuch for 1781, S. 173). This catchy judgment by the Berlin-based astronomer Johann Karl Schulze raises a number of open questions regarding the interaction between clocks, astronomical instruments, and astronomical practice.Fundamentally, when did a clock perform correctly? According to which criteria was it checked, and in how far did its going influence the quality of astronomical observation? For instance, the correct going of the clock exerted direct influence on the accuracy of the positions determined for the fixed stars. For one of the two desired coordinates, the right ascension (the measured angular distance between the star and the vernal equinox along the celestial equator), had been determined with the help of clocks since the second half of the 17th century. Yet, in comparison with the observatories in Paris and London most of the German observatories worked with inferior pendulum clocks. Were the German astronomers aware of this fact? Could they compensate for the inferior quality of their clocks? If not, did they practice a different kind of astronomy than their English and French colleagues?The project will examine the use of clocks together with other astronomical instruments. Improvements, particularly in quadrants and full-circle instruments, led to a considerably increased precision of angular measurements in the course of the 18th century. Did this improved precision influence the usage of clocks or the expectations regarding their going? Was there an interdependency between the making of astronomical instruments and the development of the concept of clocks as precision instruments?The project would like to answer these questions by analyzing written sources such as observation diaries, correspondence, contemporary periodicals and literature, as well as the systematic evaluation of the performance and technical characteristics of specific surviving clocks. In this manner, the project will differentiate the use and significance of clocks within the astronomical praxis of the 18th century, and represent them in interaction with astronomical instruments and practices.

• DFG Programme: Research Grants