c. 1000

Experimental Astrophysics

Abū ‘Alī al-Hasan Ibn al-Haytham (965–1040), Abū ar-Rayhān al-Bīrūnī (973–1048)

Ancient Greek scholars had predominantly philosophical or theoretical interests in science, especially astronomy. In contrast, the Arabic style of astronomy and mathematics that came to dominate the Middle Ages was more focused on inventing new instruments or methods, acquiring new observations, and using the data to develop new ways to address practical religious or other societal needs. This way of thinking was new: observe, record, analyze, interpret, hypothesize, repeat. It proved to be very effective, and it is basically the root of the modern scientific method.

The origins of this new, observationally focused approach to understanding the cosmos can be traced back to a small number of prominent Arab and Persian mathematicians from around the turn of the first millennium CE. One was Abū ‘Alī al-Hasan Ibn al-Haytham, a Muslim physicist and mathematician who specialized in many fields and who advocated experimentation and critical tests of prevailing theories, rather than reliance on speculation or natural philosophy (he was a critic of Ptolemy). He wrote in his Book of Optics, “In all we do, our purpose should be balanced not arbitrary, the search for truth, not support of opinions.”

Around the same time, the Persian scholar Abū ar-Rayhān al-Bīrūnī, another expert in a wide range of physical and social sciences, was advocating a similar approach to experimentation in astronomy and other fields, introducing new approaches such as repeat experiments and analysis of random and systematic errors on derived results. “I do not shun the truth from whatever source it comes,” he wrote in his encyclopedic canon of science, Kitāb al-qānūn al-masādī.

In many ways, al-Haytham, al-Bīrūnī, and many other such polymaths of the Middle Ages were the world’s first scientists—passionate about observation and discovery across a wide range of fields, skeptical of so-called truths that could not be verified, and intrinsically self-critical. Such traits have gone on to serve scientists well for more than a thousand years.

Arab astronomers study the heavens in this medieval European print from a commentary on Cicero’s first-century-BCE Somnium Scipionis (Dream of Scipio).