The Hockney–Falco theory claims that early Renaissance painters used concave mirrors to aid their depth perception (e.g., Jan van Eyck’s Portrait of Giovanni Arnolfini ni and His Wife; Fig. P24.102A). Reportedly, van Eyck traced the reflected image from his subjects according to the schematic shown in Figure P24.102B. Calculate the diameter of the blown-glass sphere from which the reflective mirror was cut and comment on the likelihood of such a theory.