Abstract
The ultimate limit of physics is not a theoretical limit, but rather an experimental one; without testable results (at least in principle), any purported theory could not be said to be physical, or even an application of the scientific method. Using a few basic tools from modern physics, this essay is an attempt to deduce those ultimate experimental limits.
This analysis ascribes a central importance to the very successful variational principles (VPs) used in both general relativity and quantum theory. Applying such VPs in some measureable 4D region of spacetime requires one to constrain partial-information boundary conditions on the 3D (hypersurface) boundary of that 4D region. Given the key premise that the constrained, mathematical boundary conditions in VPs directly correspond to values constrained by actual external measurements, one can build up a probabilistic block-universe framework that seems capable of encompassing future developments towards a general theory of measurement and quantum gravity. A general analysis of the ultimate experiments explainable by such a theory yields a reasonable estimation of the limits of physics.
Ken Wharton