# Velocity Addition & Doppler

Canonical: https://manyspace.aporia.systems/topics/velocity-addition-doppler-phy-sr-079
Updated: 2026-10-13

Physics · Special Relativity · PHY-SR-079

- Difficulty: 3 / 5
- Importance: 4 / 5
- Study time: 3.5–7 h

relativistic velocity addition, relativistic Doppler effect

## Why it matters

Galilean intuition fails at high speeds; SR redefines space, time, momentum and energy — required for QM, particle physics and GR.

## Where it is used

GPS time corrections, particle accelerators, nuclear energy E=mc^2, relativistic electronics, astrophysics.

## How you know you have learned it

Explain/derive key result from memory + solve 2 non-routine checks.

## What you need first

- [Integration by Parts](https://manyspace.aporia.systems/topics/integration-by-parts-mth-calc2-140) (helpful)
- [Electric Charge & Coulomb's Law](https://manyspace.aporia.systems/topics/electric-charge-coulomb-s-law-phy-eandm-053) (helpful)

## Resources

- Introduction to Special Relativity (French) — A. P. French
- Introduction to Special Relativity (French) — A. P. French
- Spacetime Physics — Taylor & Wheeler