Thinking Dark Anew

Abstract

Dark(ness) is                                                                                                                                                                                                                 Our blindness                                                                                                                                                                                                                  To other lights

Light by its gradations always speaks of its other, the dark. But as opposed to light which we assume we know the nature of, the nature of dark remains elusive. A key reason for this is that dark is often defined in terms of (absence of) light, and light in turn in relation to the sensibilities of our vision, which makes the demarcation line between light and dark rather arbitrary and difficult to define.

I explore the nature of dark by considering a set of thresholds of dark and ask what the limit of such thresholds may be. Starting with the limitations of the human vision, and those of other species – as well as the physical properties of the electromagnetic waves of which the visible part, light, constitutes a very small part - I define the notion of relative darkness, in relation to any limited vision. The observer-dependence of this definition raises the interesting question of possibility of absolute darkness - i.e., dark(ness) for all possible visions, whether biological or artificial, terrestrial, or extra-terrestrial - defined as the absence of electromagnetic waves across their entire range of wavelengths.

I argue that as opposed to relative darkness that does exist in the natural world, at least within the limits of the sensitivity of our (or any other limited) vision, absolute darkness does not naturally occur in the Universe at present. Furthermore, strictly speaking, it cannot be constructed artificially through any physical process which involves a finite number of steps. I explore the possibility of absolute darkness occurring in the very far future of the Universe and argue that only asymptotically in time (assuming the Universe is future eternal), can the Universe possibly tend towards such a state. But long before such epochs the Universe is likely to be devoid of any observers, with its physics becoming more and more uncertain given our present knowledge. 

I also briefly discuss the colour black and ask whether absolute black can exist in the Universe. I argue that this is similarly unlikely.

Despite the observer-independent nature of the discussion here, dark (and black) carry deep psychological and metaphoric meanings for us. The conceptual realisation of the impossibility of absolute dark in our Universe, where all possible visions would fail, can have great symbolic significance, as well as reminding us of the vast vistas open to other possible visions, that forever remain closed to our eyes