Cosmology, Sacrobosco, and Planetary Models

Vocabulary flashcards covering Johannes Sackro Bosco, medieval university astronomy, printing history, and historical debates on cosmological models.

Johannes Sackro Bosco

A teacher at the University of Paris in the 1200s whose lectures and writings, including The Sphere and the Algorithmus, formed standard university curricula.

Algorithmus

A short book by Sackro Bosco introducing place-based notation and Hindu numerals to Europe, derived from the earlier work of Alfarizmi.

Alfarizmi

An Islamic mathematician active in Baghdad approximately 400 years before Sackro Bosco who referred to place-based numerals as Hindu numerals.

The Sphere

A foundational university textbook authored by Sackro Bosco based on his Paris lectures, widely printed in small, inexpensive Latin editions to teach the two-sphere model and cosmology.

Two-sphere model

A cosmological framework describing a spherical Earth positioned at the center of the cosmos surrounded by rotating spherical heavens.

Armillary sphere

A three-dimensional instrument made of wood or metal rings, originally described by Ptolemy, used as a teaching device to demonstrate the celestial spheres and central Earth.

Eccentric model

A mathematical technique used by Ptolemy to account for the apparent speeding up and slowing down of planets by shifting the observer away from the center of uniform circular motion.

Retrograde motion

The apparent backward movement of a planet across the zodiac, represented geometrically in Ptolemaic astronomy using an epicycle carried along a deferent.

Deferent

The primary circular track in Ptolemaic models upon which a smaller circle, the epicycle carrying a planet, is rotated.

Theories of the planets

A textbook tradition that arose alongside The Sphere, concentrating specifically on two-dimensional geometrical calculations to predict planetary positions.

Realism

The philosophical position that scientific models are intended to capture and describe underlying physical reality.

Instrumentalism

The philosophical perspective that treats scientific models primarily as useful calculating instruments to yield accurate predictions, without requiring that they represent physical reality.

Ibn al Haifa

An Islamic scholar (also referred to as Al Khazan) who attempted to reconcile two-dimensional predictive geometric planetary models with three-dimensional physical reality.

Orbach

An astronomer whose printed lectures presented a new theory illustrating the real three-dimensional configuration and motion of celestial spheres using hand-colored cross sections.