Becoming familiar with sleep

I have been paying close attention to my sleep patterns, aided by my Apple Watch and a new CPAP machine which is helping sleep more deeply.  As a result I am becoming increasingly familiar with how sleep works, from the phases of REM, to the waves of light and deep sleep I go through. I've been surprised to learn that waking up is a normal and healthy part of sleep (although waking up because you can't breathe is not, hence the sleep therapy).

So things catch my eye, and today's rabbit hole is aided by this article which describes more ancient and natural human sleep patterns during which a period of wakefulness is common and expected.  

For most of human history, a continuous eight-hour snooze was not the norm. Instead, people commonly slept in two shifts each night, often called a “first sleep” and “second sleep.” Each of these sleeps lasted several hours, separated by a gap of wakefulness for an hour or more in the middle of the night. Historical records from Europe, Africa, Asia and beyond describe how, after nightfall, families would go to bed early, then wake around midnight for a while before returning to sleep until dawn.

Sleep patterns and managing the kind of light I am exposed to before bed and in the morning is radically changing how I feel during the day in the first couple of weeks of this new regime. Combined with the therapy, I am much better rested, even with less than 8 hours in bed. No midday sleepiness, less grogginess in the morning. On this trip I have handled jet lag better and recovery from a cross-country redeye has been easier on my system than usual.