Shortness of Dark
`Regardless of who deserves the most credit in its invention, before the incandescent bulb began to proliferate in the early twentieth century, human sleep schedules were largely governed by the Earth’s day and night cycle. But once humans possessed the technology to ward off an appreciable chunk of nighttime, we soon extended our usable waking hours by an average of 13%. Some researchers believe that this modern convenience, credited with bringing the human race in from the dark, may also be responsible for numerous ills. [..]
Once humans began to use artificial light to vary the length of the day, the average night’s sleep decreased from about nine hours to about seven, and the amount of sleep began to vary considerably from one night to the next. This irregularity prevents one’s circadian rhythm from settling into a pattern, and creates a state of perpetual semi-jet-lag. Our bodies’ rhythms attempt to appropriately adjust our alertness, blood pressure, and such for particular times of day; but we often do things contrary to this cycle, and therein lies the problem.’
