I have a luminous watch that I wear at night. Even though I put it on a south-facing window ledge to refresh it during the day, the dial has always been very faint. One night, finding it impossible to read the time, I flashed an LED bicycle light at it for a second. The watch immediately became very bright. How can one second of torchlight have more effect than a whole day of sunlight?
P. J. Stewart, Oxford, UK