Modern & Quantum Physics

Modern and quantum physics comprises the theoretical revolutions that overturned classical intuition in the early 20th century. Special relativity, introduced by Einstein in 1905, replaced Newtonian absolute time with a unified spacetime and established the equivalence of mass and energy through $E = mc^2$. General relativity extended these ideas to curved spacetime, providing a geometric description of gravity that predicts black holes, gravitational waves, and the large-scale dynamics of the cosmos. Quantum mechanics, developed by Planck, Bohr, Heisenberg, Schrodinger, and Dirac, describes matter and energy at atomic scales through wave functions, operator algebras on Hilbert spaces, and the probabilistic Born rule. Quantum field theory synthesises special relativity and quantum mechanics into a single framework, treating particles as excitations of underlying fields and yielding the spectacularly successful Standard Model of particle physics. These four sub-topics — special relativity, general relativity, quantum mechanics, and quantum field theory — form the conceptual core of contemporary physics and underpin virtually every frontier research programme.