boredroom’s Reviews > The Discovery of Time > Status Update

This low-point occurs 2 to 4 hours before their usual wake-up time. Understanding this can help enormously when coping with things such as jet-lag or a dramatic change in daily routine.

In humans, the changeover point from the delaying shift to the early morning advancing shift takes place around the time when the core body temperature is at its lowest daily point - this happens to me during this monsoon season. I've been waking up early these days, woken up by trips to the looooooo!

How does the required resetting occur? The circadian clock's sensitivity to light comes in. Scientists have found that the internal human clock is designed so that the exposure to early morning light produces a shift forward in the circadian cycle, while light exposure around dusk produces a slight backward shift.

Conversely, if the person's internal clock were to run naturally fast, to a 23hour subjective day, then it would have to be reset backward by 1hour each day.

Human has a circadian clock at exactly 24 hours. If a human circadian clock runs naturally slow at 25 hours, the person would naturally want to sleep and wake up each "day" one hour later than the previous day. Thus in order to catch up and remain in step with the 24hour world, this person's slow internal clock must be shifted forward by 1 hour each day.

Circadian clocks has evolved two features: sensitivity to light and lack of dependence on temperature.

Bees could locate a food source by using the "azimuthal" position of the sun - the point on the horizon directly below the sun - as a compass. It is remarkable because the azimuth changes by 15 degrees per hour as the sun steadily tracks across the sky. To use the azimuth as a directional cue, the bee must know the time of day, make continuous adjustments in its direction of movement relative to the azimuth.

The day and its hours - the division of each 24th of the day into 60 minutes is a relic of a completely different system: the Mesopotamian base-sixty arithmetic.

The week was invented by the Romans with each day named for the god who governed its first hour, and they passed the system on, eventually almost to everyone.

The Gregorian calendar, the present day system of timekeeping, is the best attempt to date (and still a necessary imperfect one) to reconcile conflicting time signals from the changing seasons, the sun, the moon, and the stars. It worked so well that it seem like some absolute insight into the way God organized time in the beginning.