Medina, 27 January 632 CE: As daylight begins to fade, Prophet Muhammad (PBUH) rises to perform Salat al-Kusuf, the special prayers offered during a solar eclipse. His infant son Ibrahim died that day, prompting some to whisper that the Sun darkened because of his loss. But the Prophet (PBUH) rejects the superstition: the Sun and Moon do not eclipse for the birth or death of anyone, he teaches, urging people to pray and invoke Allah until the light returns.
The moment, as mentioned in the Hadith, remains one of the clearest early examples of how Islam directs believers to respond to celestial phenomena—with awe and humility, but without superstition. Nearly fourteen centuries later, the sky is preparing to darken once more. On August 12, as the first total solar eclipse visible from the Iberian Peninsula in more than a century sweeps across Spain, the spectacle puts the spotlight back on another age—to the 11th-century Andalusian astronomer Al-Zarqali, who studied the movements of the heavens with unprecedented precision.
Toledo lies just beyond the path of totality, yet the Moon will conceal about 99.3 percent of the Sun, leaving only a razor-thin crescent of fire above the ancient city. In the 11th century, Toledo was part of a Muslim emirate, formed after the disintegration of the mighty Andalusian state. The Romans had called the city Toletum; in Arabic it became Tulaytula, an adaptation of the older name, before the Spanish form Toledo emerged. Built on a steep granite hill and enfolded on three sides by the river Tagus, the city was the centre of an independent Muslim-ruled taifa.
Al-Zarqali’s observations helped shape the Toledan Tables, astronomical charts used to predict the movement of the planets. His astronomical works travelled across linguistic and religious frontiers through Latin translation. Centuries later, 16th-century astronomer Copernicus cited him by his Latinised name, Arzachel, in De revolutionibus orbium coelestium. Emilia Calvo Labarta, a scholar of medieval Arabic astronomy at the University of Barcelona, says that “the Toledo group carried out observations over a long period.”
“It was not only Al-Zarqali, but several astronomers working together… We have the treatises and astronomical handbooks they wrote, as well as the data they collected,” Calvo explains. Al-Zarqali appears in scientific literature of the period as an exceptionally skilled maker of instruments. Largely self-taught in astronomy, he worked with Said al-Andalusi, a judge and historian in Toledo. Al-Zarqali’s ability to turn metalwork, geometry, and celestial measurement into one practice eventually made him the group’s leading figure.
“His achievements rested on long-term observation: the sources attribute to him 25 years of observations of the Sun and 37 years of the Moon,” Mustafa Kacar, head of the History of Science Department at Fatih Sultan Mehmet Vakif University, tells. “This continuity enabled him to calculate solar and lunar parameters and to question values inherited from Ptolemy. The observations made in Toledo were essential for the development of later European astronomy.”
Al-Zarqali did not merely record the sky; he redesigned the tools through which it could be calculated. A conventional astrolabe required specific plates for different latitudes. His universal plate, the al-safiha al-zarqaliyya—known in medieval Europe as the saphaea or azafea—used a new projection so that one instrument could function anywhere. “He found a mathematical solution for representing this on a single plate,” Kacar says. “In practical terms, it was an instrument that could be used at almost any inhabited latitude.”
The first version was so dense with intersecting grids that Al-Zarqali wrote a 100-chapter guide to its use; he later designed a simpler version, the shakkaziyya, accompanied by a 60-chapter treatise. Castilian, Latin, and Hebrew witnesses are dispersed across other collections, while a 12th-century safiha zarqaliyya survives in Barcelona. These physical artifacts serve as a testament to the sophistication of Andalusian scientific inquiry during the Middle Ages.
Prepared by historian of science Fuat Sezgin and opened in 2008, the museum in Istanbul turns descriptions recovered from manuscripts into a collection of copies, models, and instruments. “As a result of the Orientalism that began in the 19th century, we forgot these works while learning to remember and accept figures such as Leonardo da Vinci,” Kacar says. The recovery of these texts and tools is vital to understanding the true lineage of modern scientific thought.
Calvo points to ninth-century experiments involving Baghdad and Mecca, as well as similar work by Al-Biruni in the 11th century, as evidence of a broader scientific culture. “Astronomers had known since antiquity how to forecast eclipses,” Calvo says. “By registering them in different places, they could use the difference in local time to calculate longitude.” This methodology allowed for the creation of increasingly accurate maps and navigation charts that would eventually facilitate global exploration.
The legacy of the Toledo group remains a cornerstone of the history of science, bridging the gap between ancient Greek knowledge and the Renaissance. By challenging established Ptolemaic values, Al-Zarqali and his peers fostered a culture of empirical verification. Their work proves that the scientific revolution was not a sudden European event but a gradual process built upon centuries of cross-cultural collaboration and rigorous observation.
As the moon obscures the sun over the ancient walls of Toledo today, the shadow serves as a reminder of the enduring nature of human curiosity. Just as Al-Zarqali looked to the sky to refine his understanding of the universe, modern observers continue to find value in the intersection of history and science. The instruments he crafted and the tables he calculated remain symbols of a time when Toledo was a beacon of intellectual light, illuminating the path for future generations of astronomers.
“With the equatorium, many of those calculations could be avoided.” His design placed the deferents and other circles of the planets on plates that could be manipulated instead of recomputed line by line.
In the 1543 first edition of De revolutionibus, the name “Arzachel Hispanus” appears alongside other authorities whose measurements he examined.
He also devised an equatorium that converted planetary models into a working instrument.
Drawing on decades of observation, he argued that the solar apogee slowly shifted against the fixed stars and developed a model that influenced astronomers through the age of Copernicus.
What he inherited were observations, parameters and mathematical devices that could be rearranged inside a radically different cosmology.
Europe often retained the calculation even when the person behind it became difficult to recognise.
“The trail did not disappear altogether.
Al-Zarqali’s design is therefore not only preserved on the page; in Istanbul, it can be seen again in three dimensions.
Kacar says Latin translators were selective, concentrating on mathematics, astronomy, medicine, chemistry and philosophy.
He identifies a second layer of erasure in modern historiography.
He draws on a wider thesis associated with Fuat Sezgin: European science did not emerge in isolation, but was shaped by accumulated knowledge from Islamic civilisation.
As Toledo falls into near darkness on this August afternoon, the sliver of sunlight will be a fitting image for a body of knowledge that survived conquest, migration and the loss of its original language without ever disappearing entirely.