Editing Attractor (section)

=== Limit cycle ===
{{main|Limit cycle}}
A [[limit cycle]] is a periodic orbit of a continuous dynamical system that is [[isolated point|isolated]]. It concerns a [[Attractor network|cyclic attractor]]. Examples include the swings of a [[pendulum clock]], and the heartbeat while resting. The limit cycle of an ideal pendulum is not an example of a limit cycle attractor because its orbits are not isolated: in the phase space of the ideal pendulum, near any point of a periodic orbit there is another point that belongs to a different periodic orbit, so the former orbit is not attracting. For a physical pendulum under friction, the resting state will be a fixed-point attractor. The difference with the clock pendulum is that there, energy is injected by the [[escapement]] mechanism to maintain the cycle.

[[File:VanDerPolPhaseSpace.png|center|250px|thumb|{{center|[[Van der Pol oscillator|Van der Pol]] [[phase portrait]]: an attracting limit cycle}}]]