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Commentary on the model of the world machine

Tanner, Brian; McLeish, Thomas; Sonnesyn, Sigbjorn; Falk, Sebastian


Thomas McLeish

Sigbjorn Sonnesyn

Sebastian Falk


Giles E. M. Gasper

Tom C. B. McLeish

Sigbjørn Olsen Sønnesyn

Hannah E. Smithson


The chapter provides both a commentary and a science-based explanation of the text of On the Sphere. It contains many diagrams, designed to clarify the geometrical constructions on which the narrative is based. Presented in alignment with the paragraphs of the text, the chapter falls into three principal sections. The first defines the structure of the universe in terms of nested spheres, presents the case for a spherical earth and describes the circles in the heavens corresponding to the motion of the sun and fixed stars. The second section relates to the motion of the sun through the year, the variation of the length of day with season and latitude, the eccentricity of the solar orbit and the precession of the equinoxes. Finally, the motion of the moon on its eccentric orbit is examined, concluding with a detailed discussion of lunar eclipses.


Tanner, B., McLeish, T., Sonnesyn, S., & Falk, S. (2023). Commentary on the model of the world machine. In G. E. M. Gasper, T. C. B. McLeish, S. Olsen Sønnesyn, & H. E. Smithson (Eds.), 'Mapping the Universe: Robert Grosseteste’s De sphera - On the Sphere (132-166). Oxford: Oxford University Press

Publication Date May 12, 2023
Deposit Date Jan 17, 2024
Publisher Oxford University Press
Pages 132-166
Series Title The Scientific Works of Robert Grosseteste
Series Number Volume 2
Book Title 'Mapping the Universe: Robert Grosseteste’s De sphera - On the Sphere
Chapter Number 4
ISBN 9780198805526
Public URL
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