At a certain time of day if you have a headache that makes the outside light hard to take you close the blinds. And the light filters through the venetians in such a way as to create a pattern that you find interesting and snap a photo. Because the sun will move and the pattern will disappear. And tomorrow maybe the light will be different and maybe you'll keep the blinds up because the drugs will have taken effect and you'll have forgotten all about the headache and the light and the blinds and you and the sun will have both moved on. But this will remind you...