The mnp Model, a model of everything based on three tiny basic entities with two types of interaction, happens to demonstrate charge/time symmetry in the first and probably second order. This is considered an interesting accident by the author, and is not considered part of the proof of concept studies nor part of the feasibility of concept studies. Like mass, rest mass and relativistic mass, CT symmetry just emerges from the interactions of the basic entities that comprise the Model. For those who just wandered in to the discussion of the mnp Model, this may be far as you want to venture into the explanation. The author remains assured that "no one is thinking like this," so this short note will remain a very abstract abstract to most readers.
In the mnp Model, the three basic entities, m, n, and p, are very small and have a very small range of influence. The mediators, m's, have a travel direction and an axis related to polarization/charge perpendicular to that travel direction. The basic entities of negative charge, n's, have a travel direction and the axis is oriented to the reverse of travel direction. The basic entities of positive charge have a travel direction and the axis of polarity/charge is the same as travel direction. All entities are seen as traveling at c. If time were to be reversed, the axes would be unchanged. The direction of travel for all the basic entities would be reversed.
The two interactions of the entities can be summarized quickly, even if understanding the ramifications of such simple interactions is an ongoing project and is still being developed. The Travel effect is the attempt by basic entities to travel in the same direction or in the opposite direction. Entities traveling at 90 degrees to each other have no effect on each others travel direction. The Axis effect is the attempt by basic entities to have their axes line up exactly. At 90 degrees, the axes of two entities would still try to align, eventually at the average of their axes. At 180 degrees, the effect of Axis alignment is negligible.
With time reversal and hence travel direction reversed, mediators, m's, would still behave like mediators, since the polarity/charge axis remains perpendicular to the new travel direction. Negative and Positive switch roles, so what was a p now has a polarity/charge axis the reverse of travel and the n's now have an axis pointing the same direction as travel. The Travel effect, the attraction between basic entities to travel in the same or in opposite directions, is the basis of gravity, the cohesion of the 1/6th of charge in quarks and most of the cohesion of the 1/6th of charge in electrons and positrons, the attraction of mediators to contribute to mass in moving particles and to the actively moving 1/6ths of charge in the quarks making up nucleons. So the mediators are seen as the basic entities that play many of the roles assigned by modern physics: gravitons, fhotons, neutrinos, the extra mass of quarks compared to electrons and positrons, gluons attracted by the quarks as they fight over each others charge structure, the extra mass in muons, taus, and the larger quarks, the additions to mass called relativistic, and most of the energy in gamma rays.
The Travel effect in the mnp Model is bidirectional, so a reversal of time with a reversal of travel direction leaves the attractions of basic entities to travel in the same or opposite directions intact. Gravity is unchanged. At the fhoton level, electromagnetism and light are unchanged except for traveling in an "opposite" direction. The Axis effect is NOT bidirectional. Axes try to line up exactly, so that two basic entities with axes in any different directions (except 180 degrees difference) will attempt to align their axes. What had been p's now have their axis anti-parallel to travel (as the n's did in the time forward universe) and n's now have their axis parallel to travel (as the p's did in the time non-reversed universe). If the thought experiment were applied to an atom, the former electron shells would be positron shells and the nucleus would now be made up of anti-quark, behaving as we might expect atoms to behave but with opposite charges.
Whether the mnp Model contains within itself the root to subtle time non-symmetry that would chase differences in decay times for kaons and anti-kaons as seen at CERN in 1993 is not an issue at present. Tweaking the mnp Model to accommodate one experimental result is currently (no pun intended) not attractive. The mnp Model has far more difficult experiments to explain, like magnetism.
Conclusion
The author sees the CT symmetry thought experiment as interesting. Since the mnp Model intends to provide mechanism and explanation for all experiments, it may be an entrant in the "first to explain CT symmetry" race. Yuck. Because the mnp Model posits a one way direction to time, the movement of ALL the constituents occurring at c, and an abject physicality at the level of the basic entities, with measured space being a result of interaction between particles and gravitons, he sees this thought experiment as not very convincing. But the possibility that the mnp Model will be a gauge model for other theories someday has not been precluded, and mathematical conveniences like time reversal in quantum electrodynamics and quantum field theory are at least not prohibited.
Notes
This consideration of CT symmetry is inspired by Martin Gardner's The New Ambidextrous Universe, Dover 2005 with a new preface and new notes for the reprinted 1990 3rd edition. The history of the loss of parity (P) symmetry in "weak" interactions from the later 1950's prompts the author to shrug with an "of course." Spin in the mnp Model is the result of the geometrical structure of fermions, with six quantized loops in a strand, coiled. The imbalance of the coiling of the closed loops leads to spins of 1/2 and the loss to two coils to absorb energy and the gaining of two coils to release a quantum of energy changes the sign of the spin (or increases the magnitude by 1). Fhotons and neutrinos are not seen as containing any spin themselves, but of causing its appearance in electron shells and nucleons when energy is absorbed or released. So from the mnp Model's point of view, P conservation should not be expected in "weak" interactions. The author sees no way to rescue parity and put it back into a symmetry relation. On the other hand, CT is symmetrical. Just not realistic.
Good writers in the field tell me that writing about physics to be understood by the lay person is terribly hard. Staying true to the science in its details is impossible. Yet Martin Gardner consistently created readable, understandable explanations of various phenomena, both mathematical and physical. He seems to have had unparalleled access to scientists and mathematicians and an unparalleled access to quotes from those inside and outside his fields of investigation. Rather a Forrest Gump of science popularizers. Miss you, Gardner, but I also have benefited from many who have you as a model to emulate and to which to aspire.
Humor
Perhaps some will find an explanation of "Why CT Symmetry?" engauging. A singular thought.