Chapter 2: Basic Physics – Core Principles

The scientific method, relying on observation, reason, and experiment, provides the framework for discovering these rules, which are checked through simple experiments, deriving less specific laws, and rough approximation. Historically, physics has progressed by the "amalgamation" of previously separate classes of phenomena, such as unifying heat with mechanics (atomic motion) and electricity and magnetism with light (the electromagnetic field). Before 1920, the world was largely understood classically, with particles (initially 92 atomic types) moving in three-dimensional space and time, acted upon by weak, long-range gravitation and stronger, short-range chemical forces. This classical view accounted for basic properties of matter like wind, pressure, and heat via the movement of particles. The short-range forces were eventually identified as the powerful electrical interaction, governed by positive and negative charges (likes repel, unlikes attract), which explains atomic balance and structure far better than gravity, which is enormously weaker. The structure of the atom was refined to include a small, massive, positively charged nucleus (protons and neutrons) surrounded by light, negative electrons, where chemical properties depend solely on the number of outer electrons. This strong electrical interaction is best described not by direct action, but by the concept of an electromagnetic field that charges create and through which disturbances propagate as waves (like radio, light, and x-rays). The subsequent revolution of quantum mechanics, arising after 1920, revealed that classical laws fail at the small scale and introduced the idea of space-time, replacing the Newtonian stage. Quantum mechanics dictates that a particle cannot simultaneously have a definite position and momentum (the Uncertainty Principle), which is the physical mechanism preventing electrons from collapsing into the nucleus. Furthermore, quantum theory established that fundamental events are statistically determined, making precise prediction impossible, contradicting long-held philosophical tenets of science. The theory successfully unified particles and waves into a single concept. The resulting theory for light and matter interaction, Quantum Electrodynamics (QED), is one of physics' greatest achievements, requiring only the electron's mass and charge to explain nearly all ordinary phenomena, and predicting corresponding antiparticles. However, the physics within the nucleus, involving extremely powerful nuclear forces mediated by particles like the pion, remains largely unsolved because theoretical calculations are prohibitively difficult. Today, this domain is complicated by the proliferation of approximately thirty known particles—including baryons, mesons, and leptons—which are only partially categorized using concepts like "strangeness," confirming that physicists have yet to find a complete and unified law for the strongest fundamental interactions, though the laws for electromagnetic, weak, and gravitational interactions are largely known.