Why You Can Never Reach the End of a Rainbow

Why can you walk toward a rainbow and never arrive at its coloured end? Follow light into a water drop, trace its partial reflection and refraction, then build the viewing cone around the direction opposite the Sun. Moving your eye selects different droplets. A finite shower can also make the bow fade. Original ray calculations and Blender diagrams explain viewing directions; they are not footage of photons or physical coloured rings. The illustrative refractive-index ratio 4/3 gives a primary angle near 42 degrees and a secondary near 51 degrees. Angles depend on wavelength and optical conditions. Distances, marker speeds, ray separation and model time are schematic. The simple spherical-drop ray model omits wave interference, the finite solar disc and distorted large drops. English narration: Michael. Original script, ray calculations, Blender model, motion graphics and editing: Matter Made Clear. No music. English captions supplied. Chapters 0:00 The end moves with the observer 0:47 Put the Sun behind the viewer 1:35 Trace one route through one drop 2:26 Why one angle becomes bright 3:24 Color changes the direction 4:22 Turn the angle into a cone 5:12 Move the eye, change the droplets 6:04 Where the rest of the circle goes 6:58 A second reflection makes another bow 7:55 An angle, not an address Scientific sources NOAA / NASA JPL, what causes a rainbow: https://www.nesdis.noaa.gov/about/k-1... US National Weather Service, rainbow geometry and primary/secondary paths: https://www.weather.gov/fgz/Rainbow NASA Chandra / Smithsonian Astrophysical Observatory, rainbow ray paths: https://chandra.harvard.edu/edu/stop/... Robert Greenler, University of Wisconsin-Milwaukee physicist, original explanation of curved rainbows: https://www.scientificamerican.com/ar... Hong Kong Observatory / Jeffrey Lee Chi-wai, the shape of raindrops: https://my.weather.gov.hk/en/educatio... Moving footage and credits Mixkit / @dubassy, Niagara Waterfalls, clip 4323: https://mixkit.co/free-stock-video/ni... Mixkit Stock Video Free License: https://mixkit.co/license/#videoFree Source excerpt 0.3–6.6s at supplied playback rate; original recorded timelapse. Acquisition time compression and spatial calibration were not supplied. It shows sunlight, spray and a rainbow; it does not measure observer motion or individual drop brightness. No source audio is used. All explanatory graphics are original. No scientific-source artwork or competitor footage is reproduced.