Modern engagements with medieval science: sensing and perceiving light and sound

What information awaits us in the external world, and how is such information represented internally? Far from being solely modern reflections, these questions recur throughout intellectual history. With the present work, a step is taken towards a more accurate appraisal of medieval scientific thought and practice. The benefits of doing so lie not only in a more faithful picture of the past; by engaging with historical science we find insight and inspiration for novel research in diverse areas. This is reflected in the variety of topics and disciplines presented here, which would not surprise the well-rounded natural philosopher of the thirteenth century. The principal objects of study are light and acoustic waves, and their associated sensory phenomena of colour, rainbows, material appearance, sound, and speech.
In part i, the methodologies and concepts of medieval science, relevant to this work, are introduced and discussed. The writings of Robert Grosseteste on colour, the rainbow, and speech, are contextualised within the medieval world and explored.
Part ii presents research on the rainbow, as it was understood in the thirteenth century by Grosseteste. Evidence from physical experiments and optics simulations show it likely to be the first theory of its kind based on direct observation. Grosseteste’s rainbow mechanism is then compared, and found analogous to, the geometric optics of another atmospheric halo—Parry’s arc.
Part iii again engages with the writings of Grosseteste. First, the medieval conceptions of perception, and their commensurability with contemporary studies are discussed. This is done through the lens of aspectus and affectus, which we find in Grosseteste’s treatise on the liberal arts. Then, his treatise on speech production, perception, and phonetics is explored with an interdisciplinary approach. His combinatorial, geometric scheme of figures—which he implicates in a multisensory framework of mental imagery, vocal tract shaping, and the letter shapes of vowels—is interpreted through linear transformations of the two-dimensional plane. In response to this text, psychophysical experiments with artificial vowel stimuli find that such geometric figures can be incorporated into acoustic chambers giving rise to their associated vowels.
Part iv focusses on medieval art, specifically the use of materials in medieval poly- chrome sculpture, and on resultant questions of visual perception. The physical and psychophysical mechanisms of material optics and colour vision are discussed, and illustrated with a novel metamer visualisation and a public engagement installation. The material composition of polychrome imitation gold, its optical and perceptual qualities, are described.
Part v responds directly to part iv with a psychophysical investigation into material perception and the percept of metallicity. An experimental paradigm of conjoint measurement is used to unpick the contributions of metal roughness and coating properties to the metallic appearance of objects. Models employing low-level image statistics are found to be capable of replicating observer performance, suggesting a heuristics approach to metallicity judgement. An image-processing algorithm, for the automatic transformation of objects to a golden appearance, is also described.
In part vi a high-speed schlieren imaging system, with corresponding software, for the detection, visualisation, and audio recovery of acoustic waves in air is described, in response to Grosseteste’s writings on the vibrational mechanics of sound.
Part vii concludes, evaluating the successes and challenges of interdisciplinary research and looking to future work.

Keywords: Phonetics
Natural philosophy
Optics
Medieval science
History of science
Material perception
Advisor: Siviour, C
Smithson, H