A double pendulum is a pendulum with another pendulum attached to its end, and is a simple physical system[?] that exhibits rich dynamic behavior[?]. The double pendulum is governed by very complicated formulas that can be found here (http://scienceworld.wolfram.com/physics/DoublePendulum). The double pendulum relates to:
... jealously of Dolly's sister Katarina (Kitty) whom he has previously been courting.
As the novel opens, Stiva's friend Levin has returned Moscow from his country estate ...