Introduction

Why Special Relativity?

In 1905, Einstein published a paper that demolished two centuries of intuition about space and time. His two postulates — that the laws of physics are the same in all inertial frames, and that the speed of light is constant for all observers — lead to consequences that feel impossible: moving clocks run slow, moving objects shrink, and mass and energy are the same thing.

These aren't approximations or illusions. They are experimentally confirmed at particle accelerators every day. GPS satellites would drift by kilometers per day without relativistic corrections.

How This Course Works

You will implement the equations of special relativity in pure Python. Each lesson introduces one concept, explains the math, and asks you to write the equation as a function. The speed of light $c = 299{,}792{,}458$ m/s is your fundamental constant.

What You Will Learn

This course contains 15 lessons organized into 3 chapters:

1. Relativistic Kinematics — The Lorentz factor, time dilation, length contraction, relativistic velocity addition, and the relativistic Doppler effect.
2. Spacetime Geometry — The Lorentz transformation, the spacetime interval, proper time, and rapidity.
3. Relativistic Dynamics — Relativistic momentum, energy ($E = \gamma mc^2$), the energy-momentum relation ($E^2 = (pc)^2 + (mc^2)^2$), 4-vectors, relativistic collisions, and mass-energy equivalence.

Let's start with the Lorentz factor.