I appreciated Phillip G. Armour's use of coupled pendulums as an analogy for software project management in his The Business of Software column "The Chaos Machine" (Jan. 2016) but would like to set the record straight on a few technical points. Chaos is already being exhibited when Armour's machine performs smoothly, in the sense future behavior is inherently unpredictable. What happened when the machine made a hop was not that it "hit a chaos point" but apparently some "resonance disaster" that caused it to exceed the range of operation for which it was built. Moreover, "turbulence" is not an appropriate description in this context, as it describes irregular movement in fluid dynamics. Chaotic behavior does not require three variables. The most basic instance—the double pendulum, with one rod hanging from the end of another rod—involves only two variables. And the technological solution for chaos is "control," which applies to software project management as well. Setting a project in motion, even one as simple as a single pendulum, then leaving it unattended, is not a good idea. A good case in point for how an unattended project can become chaotic is the construction of the new Berlin airport.
Günter Rote, Berlin, Germany