The balance of sleep obeys to a system of double pendulum.
- the Circadian Pendulum (de circa dia : around a day), modulates the pressure of sleep according to what time it is on the internal Clock.
- the Homeostatic Pendulum depends of the individual need for sleep on one hand and of the external constraints on the other hand.

At normal state, wake and sleep follow each other according to a rythm in harmony with the day and night cycle.
For more explanations about the "Double Pendulum" see the: "Modelization of the pendulums of sleep"
Act on the cursors to modify the balance of the system.
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(The system runs with Flash Player 9.
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