The threshold of perceptible change, a fascinating concept. Try as I might, I never manage to observe the progress of twilight while concentrating on the sky. Y

The threshold of perceptible change, a fascinating concept. Try as I might, I never manage to observe the progress of twilight while concentrating on the sky. Yet glancing out the window one minute, then the very next, the difference in brightness and hue is unmistakable. Imagine reading a book in an artificially lit, climate-controlled room. If, over the course of hours, the lights gradually dim and the temperature rises, or the background noise increases, at some point you would become acutely aware of your discomfort. But you wouldn't be able to say how or when it came to be, or even if the situation had always been somewhat like this. What if the hue of the lights varied cyclically over the days of each month? Would you ever notice? There's fractal applicability to this, scaling so far as to the flux of culture of a civilization over many years. https://www.google.com/search?kgmid=/m/02txfg https://www.google.com/search?kgmid=/m/02txfg