Wonder is it true
First impressions of Bloom in Calypso suggest many differences from Stephen, one being his interest in modern experimental science. Whereas Stephen can think, at the end of the previous chapter, "My teeth are very bad. Why, I wonder," without displaying the slightest interest in the nature of teeth, Bloom brims with questions about empirical phenomena. Having only a high school education—an education from which he is twenty years removed—he comes up with some clownishly inexact answers. But he does have both curiosity and a nose for the scientific truth, as his thoughts about cats "in the dark" and black clothes in "The sun" demonstrate.
Looking at his cat's "bristles shining wirily in the weak light," he thinks: "Wonder is it true if you clip them they can't mouse after. Why? They shine in the dark, perhaps, the tips. Or kind of feelers in the dark, perhaps." It is indeed true that cats whose whiskers are cut back become spatially disoriented; they sense their environment less well and lose their grace at walking and jumping, not to mention hunting. The whiskers do not shine in the dark. Bloom's second hypothesis, however, is substantially correct. The cat's long facial hairs (known anatomically as vibrissae) are organs of touch. Lodged in follicles beneath the rest of the cat's hairs, they connect to sensitive nerve endings and register the slightest movements of air, allowing the cat to perceive things that it cannot see or directly touch. Trimming them not only profoundly alters a cat's proprioceptive sense but also distorts its picture of its near surroundings. It is fair to say that they are "kind of feelers in the dark."
Bloom's experiential sense that on a sunny day he will be hotter in his black clothes than "in that light suit" prompts him to dredge up some concepts of how solar radiation responds to different materials: "The sun was nearing the steeple of George's church. Be a warm day I fancy. Specially in these black clothes feel it more. Black conducts, reflects, (refracts is it?), the heat." The triad of technical terms perhaps comes from Bloom's high school classes, but he misremembers one of them and muddles the distinction between light and heat. A ray of light (today we would say a wave or beam of photons) encountering matter can behave in several different ways. If it is not simply "transmitted" through the material with its vector unchanged and its energy intact, it will undergo "absorption," "reflection," or "refraction." If absorbed, it imparts its energy to the surrounding material in the form of heat. If reflected, it bounces off the surface of the material at the same angle at which it approached. If refracted, it passes through the material at an altered angle. (Two other phenomena, "diffraction" and "scattering," occur when the beam is broken up into many separate beams traveling in different directions.)
The scientifically correct answer to Bloom's question is that a black material absorbs most of the incoming solar radiation. (A white material like snow will reflect most of it, absorbing only a little as thermal energy and thus acting as an insulator for the snow beneath. A red material will reflect the red wavelengths of the radiation and absorb most of the others. And so on.) But although he substitutes "conducts" for "absorbs," and then wanders off into correct terms that offer the wrong answers, Bloom's first instinct is on the right track. Conduction is the process by which "heat," once imparted to matter by the absorption of radiant energy, is transmitted from one region of the material substance to surrounding regions that possess less thermal energy. Its action in the dark clothes is thus closely related to the absorption of sunlight that imparts the energy to the clothes in the first place.