- No. 2astra/1: A Language for Historical Astronomical Models and the Geometrical Reasoning about Them
A historical astronomical model is a geometrical construction with a kinematic variable. Texts about such models do four things at once: they describe a geometry, give it numbers, show it in one position, and reason about it. We present astra/1, a small language that writes each of the four as a text of its own kind. A model is …
Gerd Graßhoff · 10 November 2026 · version 1.0 · PDF, 30 pages - No. 1Geometrical Reasoning in the History of Astronomy: Fundamentals: Models, Propositions, Steps, Rules, and What the Figure Supplies
Astronomical texts from Ptolemy to Euler argue geometrically about models: a figure, a few sentences, and inferences marked by little more than "therefore". This paper gathers what is needed to reconstruct such arguments and to check them. It distinguishes what an argument is about (a model, as pure geometry; values for its …
Gerd Graßhoff · 10 November 2026 · version 1.0 · PDF, 15 pages
Famulus Lettre is published by OpenScienceTechnology GmbH and edited by Gerd Graßhoff. Every issue is a Famulus Notebook: its sources, figures and reconstructions can be followed to their origin. An issue keeps its number and its address; a correction appears as a new version. The issues are published under the licence CC BY-NC-ND 4.0.
