The discussion centers on the relationship between singularities and manifolds in the context of General Relativity (GR) and Special Relativity (SR). Participants clarify that simultaneity is observer-dependent, emphasizing that the expanding Friedmann-Robertson-Walker (FRW) universe cannot be described using a single simultaneity convention. The conversation highlights the implications of Einstein's Equivalence Principle and the relativity of simultaneity, asserting that different families of observers can define congruences in curved spacetimes without contradicting the physics of the universe.
PREREQUISITESPhysicists, cosmologists, and students of theoretical physics interested in the foundations of General Relativity and the nature of spacetime. This discussion is particularly beneficial for those exploring the implications of singularities and the relativity of simultaneity in cosmological contexts.
