Time Dilation Lab: Two Clocks, One Reunion
Free interactive relativity lab. Change spacecraft speed and distance, predict results, and compare Earth and traveler clocks at reunion. Explore gravity and GPS timing, with an optional 3D flight deck and Earth-message experiment that distinguishes proper time from delayed arriving light. Includes equations, cited sources, classroom prompts and model limitations. Appropriate for upper-secondary, introductory college and independent learners. Requires a modern browser with JavaScript; no learner account or payment required.