On a slightly lighter note, my perusal of the online news this morning discovered this article by Elizabeth
Farrally Living in the past:it's a sign of our times, in which she relates a conversation she has overhead of someone explaining:
...that his interest in helicopters is abstract, derived from his helicopter theory of civilisations. (How, with increasing energy, societies evolve, gradually achieving lift-off but how, if the rotors over-accelerate, the culture destabilises, crashes and burns).