Despite these barriers, the number of schools trying out other timetables for adolescent students is rapidly increasing in several countries, from Switzerland to the United States.

 

A recent Danish project has eliminated timetables entirely and left the decision about when to arrive at school to the students.6 One of the teachers of this school in Copenhagen recently pointed out in a television interview that schools should be regarded as service centers, and so they are required to offer the best possible service to their customers, meaning the optimal environment for achieving the best education possible. Allowing students to sleep and work at their optimal times should definitely be part of this service.

 

The numbers connecting smoking with social jet lag are striking: among those who suffer less than an hour of social jet lag per day, we find 15 to 20 percent are smokers. This percentage systematically rises to over 60 percent when internal and external time are more than five hours out of synch.

 

As you read in the introduction, time-zone time is the temporal reference that people have lived by since the late nineteenth century, when the world was subdivided into twenty-four time zones. Before that, the temporal reference was local sun time. It is quite remarkable that we find—in the first part of the twenty-first century—that our body clocks still live very much like those of our ancestors, namely by sun time, while our entire social life has to conform to a different schedule.

 

Its entire mainland territory, which extends over almost a sixth of the earth’s circumference, is fused into one single time zone referenced to Beijing sun time.9 When people in western China look at their watch and see that it is 10:00 P.M., it is actually only 7:24 P.M. by sun time, and if they had to get up at six in the morning to go to work, it would by local sun time be only 3:24 A.M. I have been told that the western Chinese population actually doesn’t orchestrate social life by Beijing time. For example, when they come together for an early evening meal (say at around 7 P.M. local sun time), they would arrange to meet at 11 P.M.

 

In addition, patients who suffer from bipolar depression and die by suicide do so during their manic phase and rarely during their depressed phase.7 The actual act of suicide (and not merely the thought about it) takes a level of energy that depressed individuals cannot muster during their most depressed times of year.

 

The farther from the equator that humans live, the higher the overall rate of suicide, and the larger the difference in suicide rates between summer and winter.

 

It is quite remarkable how many aspects of our lives are influenced by industrialization and its consequences, isolating us increasingly from natural signals.

 

But our internal clocks are only effective if we provide them with sufficient information: with sufficient differences in daily light and darkness, or with sufficient contact to changing photoperiods and temperatures.

 

You probably guessed the rationale behind the pink glasses, the filter sheets, and the special light bulbs. After dusk and before dawn, they aimed to shield Gerry and Barbara from that part of the light spectrum that reaches our timing system most effectively (the blue parts of the light spectrum).

 

Humans are primates, and primates are mammals. The first mammals appeared on earth between 200 and 250 million years ago—a very short time in evolutionary units. To put that figure in perspective, the first primitive unicellular organisms appeared roughly 4,500 million years ago; the first cell with a proper nucleus appeared about 1,500 million years ago;7 and the first animals with bones inside their body appeared on land only 380 million years ago.

 

While birds are the end product of an evolutionary line that conquered the airspace, the ancestors of mammals conquered the night.

 

During the day our mammalian ancestors could hide in a dark and cool burrow and during the cold nights they could roam around, dodging dangerous but now potentially sluggish reptiles.

 

All our ancestors must have been night-active (most mammals still are), but we and some other mammals have reconquered the day.

 

Once the day-active birds had firmly established their dominance in the air, some of them switched to night activity. The lark is a good example of the former and the owl is a good example of the latter.

 

You see, this book is about larks and owls from b...

 

The journey of these algae during their vertical migration is quite extraordinary, considering their size. A change of depth by ten meters is equivalent to us walking eighteen kilometers. We know that algae and other plankton can travel considerably more than fifty meters during their vertical migration down and back up, which would mean that we would have to travel 180 kilometers every day. The small creatures do not swim these large distances actively. Instead, they make themselves lighter or heavier than water by filling their cell with gas bubbles or getting rid of them. 6.

 

Only about 60 percent of conceptions actually lead to a birth. The number of natural abortions of unrecognized pregnancies during their first weeks might even decrease this rate.