The process of circadian photoentrainment, where light synchronizes the internal clock to the solar day, is subconscious and not consciously perceived.

“These melanopsin ganglion cells have been shown by the Nitz Group, N-I-T-Z, up at University of Washington, and by Samer Hattar's lab and David Burson's lab, and a number of other people's labs, Satchin Panda, Prevencio, et cetera, a number of excellent labs in neuroscience to set the circadian clock and to respond best to the contrast between blue and yellow light of the sort that lands on the cells when you view the sun, when it's a so-called low solar angle, when it's low in the sky, either in the morning or in the evening, what does all this mean?”

“So, circadian photoentrainment is the word we use, entraining the circadian clock to the photic environment is completely subconscious. You're not aware of it.”