When someone is cremated, chemical energy becomes radiant light: infrared photons that escape into space at c, the speed of light. Lightward shows how far that energy has traveled since a chosen date.

1. Enter a cremation date and an optional name in the sidebar panel
2. The expanding sphere in the 3D scene grows to match the light-travel distance
3. The sidebar lists which planets, stars, and constellations have been reached
4. Hover any marker in the scene for details and passage dates

An educational metaphor, not a measurement of individual photons. Learn more on the About page.