when vs One Light Day

"四次元年表" is a project where users collaborate to build a database that encompasses all historical events, from the origins of the universe to the endless "now", regardless of the field. It aims to accurately display both temporal and spatial distances by making "where" as important as "when".

One Light Day is a free digital monument celebrating Voyager 1, humanity’s farthest spacecraft. On 18 November 2026, Voyager 1 is expected to reach a remarkable symbolic milestone: a distance from Earth that light takes approximately twenty-four hours to cross. One Light Day transforms that immense distance into a personal and interactive experience. DISCOVER THE JOURNEY Follow Voyager 1 from its 1977 launch, past Jupiter and Saturn, through the heliopause and into interstellar space. EXPERIENCE THE DISTANCE See its estimated distance from Earth, one-way light time and the countdown to the one-light-day horizon. MEET VOYAGER 1 Examine and interact with a detailed 3D model of the spacecraft that has travelled farther than any other human-made object. EXPLORE THE GOLDEN RECORD Discover the sounds, images, greetings and scientific symbols selected to represent Earth to the cosmos. FIND VOYAGER IN THE SKY Use your iPhone’s location and motion sensors to face the estimated direction of Voyager 1. SEND A SYMBOLIC LIGHT Begin with prime numbers, then encode a short human word as flashes of light. After sending it, follow a twenty-four-hour chronograph representing the photon’s journey. A FREE EXPERIENCE One Light Day contains no advertising and requires no subscription. Every experience is available to everyone. Optional contributions help maintain the app and its website but never unlock additional functionality. Voyager 1 will remain humanity’s farthest pioneer, our avant-garde in interstellar space. One Light Day is an independent educational, cultural and artistic tribute. It is not affiliated with or endorsed by NASA or JPL. Scientific distances, directions and times are estimates and are not real-time telemetry.