Part 4/11:
A critical challenge faced by entropic gravity models is understanding what exactly the entropy pertains to. In classical thermodynamics, entropy is associated with the microscopic states of a system—like the molecules in a gas or the spins in a magnetic material. But when it comes to gravity, especially on cosmic scales, what is the microscopic entity whose entropy influences gravitational attraction?
This question has stymied many models, as it’s not enough to say that entropy increases; we need a concrete microscopic picture. Without one, the idea remains speculative, and many physicists treat it as a philosophical or heuristic framework rather than a definitive theory.