So lately I have been playing with data measuring light levels throughout the day. I am fascinated With just how much my brain and eyes filter and smooth my perception of light, making me unaware of startlingly large changes.
This graph shows data taken from the same light sensor sampling over two days. The red series of data reflects UV light levels, and the blue reflects UV + Visible light levels.
Two back-to-back days can vary in duration by 40 minutes! Sure sunrise and sunset times between two days only change slightly, but cloud cover and weather has a massive impact on the light profile of the day. During darkening leading up to sunset the brightness can halve every seven-minute for two hours without it being noticeable!
Some data is just fun to play with.