Module 2
Relativity — Special and General
SR kinematics, the equivalence principle, GR as geometry, and the optical-metric equivalence.
You need to recall how Einstein framed spacetime so you can appreciate how OFT replaces it with vacuum refraction. The goal is not to re-derive GR — it is to hold the standard picture clearly enough to see exactly where OFT diverges from it.
Concepts to Cover
Special Relativity — Kinematics Time dilation, length contraction, and Lorentz transformations as traditionally taught — with c as a fundamental postulate. You need to understand what these say physically, not just how to manipulate the equations.
The Equivalence Principle The standard GR foundation equating inertial mass and gravitational mass. Why a freely-falling observer feels no gravity. Why this led Einstein to curved spacetime. OFT explains the same observations without invoking curvature at all.
General Relativity as Geometry A conceptual overview of how mass curves spacetime and how light follows geodesics. You need to understand the Schwarzschild metric well enough to see that OFT's optical metric reproduces it exactly — different ontology, identical predictions.
The Optical-Metric Equivalence The historical models of gravity as a varying speed of light — most notably Robert Dicke's polarisable vacuum model. Mathematically equivalent to GR for all observable quantities. This is the direct bridge to OFT's gravitational mechanism. If you understand Dicke, you are most of the way to OFT 3.
Resources
Lukas Rafaj — System of Pendulums: A Realisation of the Sine-Gordon Model
An exceptional resource showing how effective length contraction and time dilation manifest mechanically in a string of pendula bound by finite tension waves. Watch a relativistic soliton move down a line of pendulums. This provides exactly the mechanical clarity needed to move away from treating spacetime as a mystical fabric — relativity is just what happens when things are held together by finite-speed interactions.
Stanford / Leonard Susskind — General Relativity (The Theoretical Minimum)
Covers the Schwarzschild metric and the equivalence principle with full mathematical honesty. If you want to understand the geometry properly before seeing OFT dissolve it, this is the place.
▶ Watch the playlist on YouTube
PBS Space Time — General Relativity Series
Handles the visual geometry of gravitational time dilation, optical metrics, and gravitational lensing. Excellent for rebuilding the mental pictures.