Galileo Time and Chronobiology

Galileo Time and Chronobiology

He discovered that

what most affected a pendulum’s motion was the length of its string—and

that for any given length of string a pendulum always took the same

amount of time to make one full swing. That periodicity, he concluded,

made pendulums ideal timekeepers. Galileo’s insight led to the invention

of pendulum clocks a few decades later. And pendulum clocks, in turn,

produced something that we don’t realize is a relatively new concept: “the


Imagine life without even a rough consensus on what time it is. You’d

find a way to

within our body and brain are

biological clocks that affect our performance, mood, and wakefulness. But

you might not recall that those clocks typically run a bit longer than

twenty-four hours. Left on our own—say, by spending months in an

underground chamber not exposed to light or other people, as in some

experiments—our behavior gradually drifts so that before long we’re

asleep in the afternoons and wide-awake at night.4 What prevents such

misalignment in the aboveground world are environmental and social

signals such as sunrise and alarm clocks. The process by which our

internal clocks synch up with external cues so we wake up in time for

work or go to sleep at a reasonable hour is called “entrainment.”

In chronobiology, those external cues are known as “zeitgebers”

(German for “time giver”)—“environmental signals that can synchronize

the circadian clock,” as Till Roenneberg puts it.6 Ancona’s thinking helped

establish that groups also need zeitgebers. Sometimes that pacesetter is a

single leader, someone like David Simmons. Indeed, the evidence shows

that groups generally attune to the pacing preferences of their higheststatus

members.7 However, status and stature are not always one.

Competitive rowing is one


called “the belongingness hypothesis.” They proposed that

“a need to belong is a fundamental human motivation . . . and that much of

what human beings do is done in the service of belongingness.”

sources). Belongingness, they

found, profoundly shapes our thoughts and emotions. Its absence leads to

ill effects, its presence to health and satisfaction.8

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