Why Can't We Reach the End of the Rainbow?
A double rainbow seen from Asheville, North Carolina.
(Image credit: Grant W. Goodge/NOAA)
You'll never swim out to the horizon , and you'll never reach a rainbow's end. The visibility of both requires distance between object and observer.
Rainbows consist of water droplets being struck by sunlight in a certain way. Round, transparent drops of water refract and internally reflect some sunlight towards the observer. Different wavelengths of light refract (change angles) at different angles, so the white light of the sun is parsed into an orderly band of colors.
