[karmakaze]

> In the early 1990s, psychiatrist Thomas Wehr conducted a laboratory experiment in which he exposed a group of people to a short photoperiod – that is, they were left in darkness for 14 hours every day instead of the typical 8 hours – for a month.

> It took some time for their sleep to regulate, but by the fourth week, a distinct two-phase sleep pattern emerged. They slept first for 4 hours, then woke for 1 to 3 hours before falling into a second 4-hour sleep. This finding suggests bi-phasic sleep is a natural process with a biological basis.

Yes, a natural process for being in darkness 14 hours a day. I personally prefer to use electric light and be out of the dark ages.

[dplgk]

If they need to go back to sleep after being up for only 1-3 hours then perhaps they should have slept longer? i.e. One shift