Abstract

Over the last century, the quest to formulate physics to account for Reality has attracted a large number of theoreticians to propose various fundamental models that have tended toward a growing level of abstractness. While space and time have been largely recognized as the four fundamental dimensions that make our perceived reality, their completeness has been challenged either by positing hidden dimensions, or by exploring the possibility that space-time itself is an emergent property of measurable physics. One quantity that has not entered this exploration is frequency. Although it is featured in numerous physical contexts, it is normally implied that it is a mere parameter that is determined by the boundary conditions, or that it contains the same information as the time, period, wavelength, or energy—all supporting the notion that frequency is fully dependent on the other dimensions. In contrast, in psychophysics of vision, hearing, and touch, frequency is a quantity that appears independent, so that both its input and output are not directly dependent on perception of space and time. Also, many important engineering applications treat frequency as a variable rather than as a parameter that is constrained alongside time. This paper explores the various conventions with respect to frequency in the physical, mathematical, and engineering literatures. It scrutinizes frequency against the standard dimensions of space-time along nine properties that may be deemed universal. It is argued that in all but the most trivial physical systems frequency should be considered an additional fifth dimension of reality. More generally, it is argued that only one of these claims can be simultaneously true: 1. Time is not a fundamental, obligatory dimension of reality. 2. The universe is fully deterministic with total knowledge of past and future. 3. Frequency is a fundamental dimension of reality.