The Blind Passenger: A Parable on the Second Complementarity
Kafkas M. Caprazli
Abstract
Two twins share a boat on a foggy sea. Their lamps partition light and heat; their sum should equal one. When the sum falls short, a silhouette appears in the blade of light rising from the crack in the keel. The first law told them someone was missing. Now the boat pitches—a motion perpendicular to their daily bargain. The pitch angle reveals where on the blade the hidden figure stands. When his weight equals theirs combined, the pitch is forty-five degrees. This parable illustrates the second complementarity relation for gravitational decoherence: θ_C = arctan(μ_C/S), where μ_C is the hidden channel contribution, and S is the sum of known channels. The first relation detects incompleteness; the second locates it.