The status of energy and the vacuum remains conceptually subtle acrossmodern physics: energy is a symmetry charge, yet global conservation isnontrivial in general relativity; quantum field theory defines the vacuumthrough renormalization in a way that makes absolute offsets ambiguous; andthe Casimir effect is often misread as direct evidence for a large gravitatingvacuum energy. This paper summarizes how these issues are treated in aPrinciple of Least Information (PLI) framework equipped with an auxiliaryinfluence sector and an optional 7D two-time (Janus) embedding. PLI is usedas a model-selection prior: among empirically adequate effective descriptions,the preferred one minimizes total description length of laws and boundaryconditions. In this setting, (i) energy is emergent as the Noether charge asso-ciated with translations along an operational time direction selected withinan otherwise rotation-invariant time-plane; (ii) reduced dynamics obtainedby tracing out the influence sector are completely positive and trace preserv-ing, yielding an explicit energy-balance identity with system–environmentexchange; and (iii) the vacuum is characterized as the lowest-informationadmissible configuration given boundary conditions, with observable effectsarising from boundary-dependent differences (Casimir/Lifshitz) rather thanabsolute offsets. We compare the resulting viewpoint with standard treat-ments in classical mechanics, GR, QFT (including curved spacetime), andsemiclassical gravity, and we summarize empirical hooks and constraints.