Entropy, gravity, and an apparent violation of the second law

Abstract An interesting question to explore in physics classes is: Does gravity violate the second law of thermodynamics? If we turn to a general physics textbook for an answer, we will find little to no reference to the relationship between entropy and gravity. The same is often true for specialized textbooks. The goal of this work is to address this question by analyzing the behavior of an ideal gas in two simple scenarios: one where gravity is negligible and another where its effects play a significant role. We have shown that while gravity-driven systems may exhibit counterintuitive behaviors—such as local ordering through structure formation—the second law of thermodynamics remains valid when considering the entire system, including all emitted energy and radiation. Given the educational focus of this work and the complexity of the entropy–gravity relationship, we will omit detailed calculations that are not strictly necessary and instead focus on the simplest physical scenarios, analyzing four representative examples through simple calculations: the Sun, the limit of extreme contraction in black holes, the protostellar contraction sequence, and core collapse with neutrino cooling.

Investigación IESED