عنوان مجله
|
ARCHIVE FOR HISTORY OF EXACT SCIENCES
|
چکیده
|
The paper brings into light and discusses a concentric solar model briefly described
in Chapter 5 of Section III of ‘Abd al-Raḥmān al-Khāzinī’s On experimental astronomy,
a treatise embedded in the prolegomenon of his comprehensive Mu‘tabar zīj,
completed about 1121 c.e. In it, the Sun is assumed to rotate on the circumference
of a circle concentric with the Earth and coplanar with the ecliptic, but the motion
of the vector joining the Earth and Sun is monitored by a small eccentric hypocycle.
The ratio between the distance of the hypocycle’s center from the Earth and
the hypocycle’s radius is equal to the solar eccentricity in the eccentric model. The
model is to account for the constancy of the apparent diameter of the solar disk
as held by Ptolemy. The source of the model is unknown. Since the mechanism
employed in it clearly resembles the pin-and-slot device, whose use in mechanical
astronomical instruments has a long history from the Antikythera Mechanism
to the medieval solar, lunar, and planetary equatoria and dials, we argue that the
solar model can be positioned within this long-standing tradition and considered the
result of the correct understanding of some Byzantine prototype and thus a typical
example of the transmission of astronomical ideas via media of the material culture.
|