Broken sleep
▻http://aeon.co/magazine/psychology/why-broken-sleep-is-a-golden-time-for-creativity
Ekirch believes that humans, left to sleep naturally, would not sleep in a consolidated block either.
(...) He identified countless references to ‘first’ and ‘second’ sleeps in English. Other languages also describe this pattern, for example, premier sommeil in French, primo sonno in Italian and primo somno in Latin. It was the ordinariness of the allusions to segmented sleeping that led Ekirch to conclude this pattern was once common, an everyday cycle of sleeping and waking.
(...)
Ekirch found that references to these two sleeps had all but disappeared by the early 20th century. Electricity greatly extended light exposure, and daytime activities stretched into night; illuminated streets were safer and it became fashionable to be out socialising. Bedtimes got later and night-waking, incompatible with an extended day, was squeezed out. Ekirch believes that we lost not only night-waking, but its special qualities, to