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:
... left the band in 1979, and Brent Mydland[?] joined as keyboardist. Brent was the keyboardist until his death in 1990. Without missing a show, Vince Welnick[?] joined as ...