- Introduction
- Why Special Relativity Is Interesting
- Summary of Important Results
- The Idea of Space-Time is Pretty Simple
- Example Histories
- Grids Measure Motion
- Grids Measure Time With Many Sensors, Not One
- A Camera Is Not A Grid
- Inertial Grid
- Inertial Grid Family
- Invariants: What Family Members Agree On
- What Does Relative Mean?
- Rule Zero: The Rule About All The Other Rules
- The Problem Of Language
- Invariant #1: Speed Limit
- Examples of Fast Objects
- Geometric Points Have No Speed Limit
*ct*Is Better Than*t*- Invariant #2 - The Space-Time Interval
- Light-like, Time-like, and Space-like
- Cause And Effect
- Surfaces With Constant s
^{2} - Measure Rel-Time Dilation
- Standard Configuration Of Two Grids
- Rel-time Intervals Are Relative, Not Invariant
- Reverse The Perspective
- Warp Factor
- Measuring Intervals With Only A Single Sensor
- An Object's Wristwatch Measures The Interval
- Rel-Time Dilation Revisited
- Three Weeks To The Pleiades
- Moving Children Age More Slowly
- Rule For Uniform Motion
- Action Principles
- Boost Transformation - Overview
- Boost Transformation - Details
- Active Versus Passive Boosts
- Time Order Can Change
- Pancake Effect (Rel-Length Contraction)
- Why Rel-Size Decreases
- Does It Really Dilate/Contract?
- Invariant #3: Volumes in Space-Time
- Time Machines and Wormholes
- The Here-And-Now Is Stretched Out
- Is Rel-Time The Fourth Dimension?
- Space-Time Geometry Constrains The Rules
- Electrodynamics Pops Out Of Special Relativity
- Boosted Rel-Velocity
- Core Items Are Dimensionless
- Avoid Common Pitfalls
- How Special Relativity Relates to Other Parts of Physics
- Four Time Dimensions
- Questions To Ask Of An Author

- Grids, Sensors, and Signals
- Signals: Energy And Direction
- Light-Slice and Time-Slice
- Photon Signals
- Events On The Light Cone With Constant
*ct* - Direction: Aberration
- Aberration Preserves Angles
- Frequency: Doppler Effect
- Two Variations for the θ Angle
- Optical Effects as Non-Mysterious Prototypes
- Doppler Factor
- Brightness: Beaming Effect
- The Appearance of a Sky Full of Stars
- Angular Size
- Geometric Outline
- Apparent Velocity
- Astrophysical Jets

*Warning*: sometimes screens can subtly distort images.
For example, the author has seen small but measurable distortions in some angles, when a screen is
not using its default resolution.

Animations - Part I:

- Example Histories
- The Slowness of c In Astronomical Contexts
- Beta, Gamma, and Interval
- Inertial Grid Family
- Boost Transformation - Events
- Boost Transformation - Histories
- Boost Velocity

Animations - Part II:

- Light Cone Boost
- Aberration as Boost of Rel-Speed=1
- Doppler Effect
- Doppler Factor
- Doppler Effect and Aberration Together
- Stars From a Travelling Spacecraft (
**this one is especially interesting**) - Apparent Velocity as Intersection Point
- Apparent Velocity
- Apparent Magnitude
- Astrophysical Jets

- Terms Used, and Terms Avoided
- Resources and References
- Collected Formulas
- Version History and Errata
- Notes on Groups
- Software - Relativistic Starfield
- The github repository for this entire site.