Physics courses cover the fundamental rules governing motion, energy, forces, and the behavior of matter from the smallest particles to the largest structures in the universe. What you learn depends on your level: high school physics introduces the basics, while a university degree builds through five core areas (classical mechanics, electromagnetism, quantum mechanics, thermodynamics, and modern physics) before branching into specialized topics. Here’s what each of those areas actually involves.
High School Physics: The Foundation
Most high school physics courses focus on the building blocks. You’ll study how objects move (kinematics), Newton’s three laws of motion, basic energy and work concepts, simple wave behavior, and introductory electricity. The math stays at the algebra and trigonometry level, and problems tend to be straightforward: a ball rolling down a ramp, a circuit with a battery and a lightbulb, a pendulum swinging back and forth.
The jump from high school to college physics is significant. University courses revisit these same foundational ideas but expect you to solve problems using calculus, move through material faster, and think more abstractly. A topic you spent a month on in high school might take a week in a college lecture, with considerably harder problem sets.
Classical Mechanics
This is typically the first major course in a physics degree and the one that most directly extends what you learned in high school. Classical mechanics is the study of how and why objects move. You start with Newton’s laws, then use calculus to analyze motion with much more precision than you could with algebra alone.
The MIT introductory mechanics sequence, for example, progresses from Newton’s laws through kinetic energy and work in one, two, and three dimensions, then into the distinction between conservative and non-conservative forces (gravity vs. friction, roughly speaking), and finally into rotational dynamics, which covers how spinning and orbiting objects behave. You’ll also study momentum, collisions, oscillations like springs and pendulums, and gravitational orbits. At the advanced level, the course shifts to more elegant mathematical frameworks developed by Lagrange and Hamilton that let you solve complex problems, like a double pendulum or a satellite’s orbit, more efficiently than Newton’s original approach allows.
Electromagnetism
Electromagnetism covers electric and magnetic fields, how charges create them, and how they interact with matter. Early coursework focuses on static situations: the electric field around a charged sphere, the magnetic field around a wire carrying current. You learn a set of rules (Gauss’s law, Faraday’s law, and others) that describe these fields individually.
The payoff comes when you put them together. Four equations, known as Maxwell’s equations, unify electricity and magnetism into a single framework. They reveal something remarkable: a changing electric field creates a magnetic field, and a changing magnetic field creates an electric field. This self-sustaining cycle is an electromagnetic wave, and it travels at the speed of light, because light itself is an electromagnetic wave. From there, you can understand radio signals, microwaves, X-rays, and visible light as different flavors of the same phenomenon. Advanced coursework applies these equations to waveguides, radiation from accelerating charges, and the behavior of light in various materials, which connects to optics.
Quantum Mechanics
Quantum mechanics describes how matter and energy behave at the atomic and subatomic scale, where the rules of everyday physics break down. An introductory course typically starts with the historical experiments that forced physicists to abandon classical thinking: light behaving as both a wave and a particle, electrons creating interference patterns, and energy coming in discrete packets rather than continuous amounts.
The core mathematical tool is Schrödinger’s equation, which describes the probability of finding a particle in a given location rather than predicting a single definite path. You solve this equation for increasingly complex situations: a particle bouncing between two walls, a particle encountering a barrier it can tunnel through (something impossible in classical physics), and eventually the hydrogen atom. The course also covers the Heisenberg uncertainty principle, which sets a fundamental limit on how precisely you can simultaneously know a particle’s position and its momentum. This isn’t a limitation of measurement tools; it’s built into the fabric of reality.
At more advanced levels, quantum mechanics extends to systems with many particles, the behavior of atoms in solids, and the mathematical machinery of operators and matrices that underlies quantum computing.
Thermodynamics and Statistical Mechanics
Thermodynamics deals with heat, energy, temperature, and how they flow and transform. You’ll learn the four laws of thermodynamics: the zeroth law establishes what temperature means, the first law is conservation of energy (heat added to a system either increases its internal energy or does work), the second law introduces entropy and explains why heat flows from hot to cold and never the reverse spontaneously, and the third law sets a limit at absolute zero.
Statistical mechanics approaches the same questions from the opposite direction. Instead of treating a gas as a smooth, continuous substance, you consider it as billions of individual particles bouncing around randomly and use probability to predict their collective behavior. This is where you learn how temperature emerges from the average speed of molecules, why gases expand to fill their containers, and how phase transitions (ice melting, water boiling) arise from the statistics of huge numbers of particles. Key tools include partition functions, which encode all the thermodynamic information about a system, and ensemble methods that let you calculate average properties like pressure and energy.
Relativity
Special relativity, introduced by Einstein in 1905, addresses what happens when objects move at speeds approaching the speed of light. The two core ideas are deceptively simple: the laws of physics are the same for all observers moving at constant speed, and the speed of light is the same for everyone regardless of how fast you’re moving. The consequences are not simple at all. Time passes more slowly for a fast-moving object (time dilation), lengths shrink in the direction of motion (length contraction), and events that appear simultaneous to one observer may not be simultaneous to another.
The most famous result is mass-energy equivalence: energy and mass are interchangeable, which is the principle behind both nuclear power and nuclear weapons. Most physics programs teach special relativity as part of a modern physics course in the second year. General relativity, Einstein’s theory of gravity as the curvature of space and time caused by mass, is typically offered as an upper-level elective because the math (tensor calculus and differential geometry) is considerably more demanding.
The Math Behind It All
Physics at the university level requires a parallel track of mathematics courses. A typical sequence starts with differential and integral calculus in the first year, then multivariable calculus by the second year, which is essential for understanding fields that vary across three-dimensional space. Differential equations come next, since most physical laws are expressed as equations relating quantities to their rates of change. Linear algebra is critical for quantum mechanics, where the state of a system is represented as a vector in an abstract space.
Beyond the required courses, physics students often benefit from probability theory, complex variables (numbers with both real and imaginary parts, which appear constantly in wave equations), and advanced vector calculus. The math isn’t a separate subject layered on top of physics; it’s the language physics is written in. You can’t meaningfully study electromagnetism without multivariable calculus, or quantum mechanics without linear algebra.
Computational Physics
Modern physics programs increasingly require programming skills. Many real-world physics problems have no exact solution on paper, so you learn to solve them numerically on a computer. Common programming languages in physics courses include Python (the most beginner-friendly and now the most popular), C/C++, and Fortran, which remains in use because decades of scientific code are written in it.
The numerical methods you learn are practical tools: solving systems of linear equations, simulating differential equations step by step (using techniques like Runge-Kutta methods), Monte Carlo methods that use random sampling to estimate integrals and simulate physical systems, and algorithms for modeling diffusion, wave propagation, and heat flow. A computational physics course might have you simulate planetary orbits, model the spread of heat through a metal bar, or run a statistical simulation of magnetic materials undergoing a phase transition.
Upper-Level Electives and Specializations
By the third and fourth year of a physics degree, you begin choosing from specialized topics based on your interests. Common options include astrophysics and cosmology (the physics of stars, galaxies, and the universe’s evolution), nuclear and particle physics (the behavior of protons, neutrons, quarks, and the forces that bind them), condensed matter physics (how atoms arrange themselves in solids and liquids, which underpins semiconductor technology), and optics and laser physics.
Other electives include biophysics, which applies physics principles to biological systems like protein folding and cell membranes, geophysics, planetary science, and general relativity. Many programs also offer a research component where you work alongside a faculty member on an active problem, applying the tools you’ve learned to questions that don’t yet have answers.