Before Einstein, physics was dominated by the Galilean view: space was an empty container, and time ticked away at the same rate for everyone. Special Relativity (SR) upended this by introducing two core postulates: in all inertial frames. The speed of light (
In short, Special Relativity provided the , and Classical Field Theory provided the language . Together, they describe a universe where matter is just a local concentrated dance of underlying fields. Special Relativity and Classical Field Theory
The consequence is that space and time are not independent. They merge into a four-dimensional manifold called . In this framework, "distance" is replaced by the spacetime interval , which remains constant even as individual observers disagree on lengths (length contraction) and durations (time dilation). 2. The Shift to Fields: Classical Field Theory Before Einstein, physics was dominated by the Galilean
are the two pillars of modern physical thought that transformed our understanding of the universe from a static stage of "objects" into a dynamic, interconnected fabric of spacetime and energy . 1. The Death of Absolute Space: Special Relativity Together, they describe a universe where matter is
CFT is built on the Action Principle . We define a Lagrangian density ( Lscript cap L
) is constant for all observers, regardless of their motion.
Classical Field Theory (CFT) moves physics away from "action-at-a-distance" (like Newton’s gravity) toward the idea of —quantities assigned to every point in spacetime.