Erasmus Reinhold (22 October 1511 OS - 19 February 1553 OS) was a German mathematician and astronomer, born in Saalfeld, Thuringia. He served as professor of higher mathematics (mathematum superiorum) at the University of Wittenberg, where he became one of the most influential astronomical educators of the sixteenth century. Reinhold is best known for compiling the Prutenic Tables (Prutenicae Tabulae Coelestium Motuum, 1551), a set of astronomical tables based on the heliocentric model of Nicolaus Copernicus. These tables supplanted the earlier Alfonsine Tables as the standard computational tool for planetary positions throughout Europe.

Reinhold studied at Wittenberg, where he eventually held the chair of higher mathematics alongside Georg Joachim Rheticus, who held the chair of lower mathematics. The University of Wittenberg was a center of astronomical instruction in the Lutheran world, and Reinhold trained a generation of students in mathematical astronomy. He produced commentaries on Georg Peurbach's Theoricae Novae Planetarum and engaged extensively with the manuscript of Copernicus's De Revolutionibus before its publication in 1543.

The Prutenic Tables were dedicated to Duke Albert of Prussia - hence the name - and represented the first full computational realization of the Copernican system. Reinhold recalculated planetary parameters using Copernican theory, producing tables that were more accurate and easier to use than the Alfonsine Tables for practical astronomical and calendrical computation. Their adoption by astronomers and calendar reformers across Europe helped disseminate Copernican mathematical methods even among astronomers who did not accept the physical reality of heliocentrism. Reinhold himself left no unambiguous statement endorsing the heliocentric model as a physical description of the cosmos, a distinction that was common among his contemporaries. See Heliocentrism - History for broader context.

Reinhold's work illustrates the separation, common in the sixteenth century, between astronomical calculation and cosmological commitment. The Prutenic Tables were used by those preparing the Gregorian calendar reform of 1582 and by Tycho Brahe, Christopher Clavius, and others who did not share a single view on the physical structure of the solar system. His annotations on De Revolutionibus survive and have been studied as evidence of how working astronomers engaged with Copernicus's text on a technical level. Reinhold died in 1553 during an outbreak of plague, cutting short what had been a productive career.

• Heliocentrism - History
• De Revolutionibus
• Prutenic Tables
• Alfonsine Tables
• Gregorian Calendar Reform
• Georg Joachim Rheticus
• Nicolaus Copernicus
• Tycho Brahe

1. Gingerich, Owen. The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus. Walker & Company, 2004.
2. Westman, Robert S. The Copernican Question: Prognostication, Skepticism, and Celestial Order. University of California Press, 2011.
3. Dictionary of Scientific Biography, s.v. “Erasmus Reinhold,” Charles Scribner's Sons, 1975.