Relativistic Aberration of Light Calculator

About this calculator

This calculator computes the relativistic aberration of light: how the angle at which light is emitted, θ, appears shifted to θ′ for an observer moving at speed ratio β = v/c, using cos θ′ = (cos θ − β) / (1 − β·cos θ). This differs from classical (non-relativistic) aberration by the Lorentz-related denominator term, which becomes significant as β approaches 1.

Aberration explains why, at relativistic speeds, light sources shift toward the direction of motion in an observer's field of view — an effect called relativistic beaming or the "headlight effect." Astrophysicists rely on it to interpret observations of jets from active galactic nuclei and pulsars, and it's a standard topic in special relativity for connecting an object's rest-frame emission pattern to what a fast-moving observer actually sees.