One flash. Two pictures of the same construction.
A photon flash at the origin (orange) expands outward at c. A spherical emitter — at rest in its own frame, length-contracted in the lab — moves to the right at β = 0.6. Two geometric constructions of the same event sit side-by-side: one builds the prolate from a drifting oblate, the other builds the oblate by drifting captured points on a fixed prolate.
Keyboard: Space play/pause · R restart · ← → step t
What you’re seeing
- Animation 1
- The orange light circle expands from the origin. The teal oblate ellipse drifts to the right with the emitter. Where they intersect at any instant marks a point on the (dashed) prolate — the lab-frame contracted shape of the emitter. By the end, every prolate point has been visited exactly once.
- Animation 2
- Same flash, same prolate (now drawn solid). Each intersection point on the prolate is captured at its arrival time, then drifts at +v afterwards. The drifting captures accumulate into the moving oblate. Four labelled tracers at φ′ = 0, π/2, π, 3π/2 show individual drift trajectories.
- Parameters
- β = 0.6 · γ = 1.25 · r′ = 100 (pixels) · c = 1
Want the math? Math reference. Want to play with frames directly? Interactive Minkowski diagram.