- The Prehistory of Flight by Clive Hart
California, 279 pp, £29.75, September 1985, ISBN 0 520 05213 7
‘Theaetetus is flying’: Plato presented the sentence as a paradigm falsehood; good Aristotelians later argued that its falsity was apodictically certain. For the impossibility of human flight seemed to follow ineluctably from two seemingly irrefragable truths. First, there’s no flying without wings. ‘Flight,’ according to Aristotle, ‘is the form of locomotion peculiarly appropriate to birds,’ and it is properly accomplished by means of wings. (A stock example in the ancient logic books ran: ‘If the earth flies, it has wings.’) Secondly, men have no wings. According to Aristotle again, ‘birds cannot have an upright posture like men. For the nature of their wings is useful to them given the way in which their bodies are in fact constituted, but if they were upright the wings would be useless – as they are on the Cupids which painters depict. And it is clear that no man – nor anything else of a similar form – could be winged: for the possession of wings would be useless for them in their natural movement, and nature makes nothing contrary to nature.’ Only things with wings can fly; no man can have wings: therefore no man can fly. Flying is strictly for the birds.
Vol. 8 No. 4 · 6 March 1986
SIR: Since I have not yet read Clive Hart’s The Prehistory of Flight I am at something of a disadvantage. However, I must take issue with some of Jonathan Barnes’s contentions (LRB, 23 January). ‘A flying machine must be both light enough to get lift and powerful enough to achieve thrust.’ Well, yes, up to a point. But lift is in fact a function of both weight and aerodynamic efficiency. The greater the forward speed of the aircraft, and the more efficient its wings, then the greater its lift. Weight is not the overriding factor. And it was the lack of any engine with a decent power-to-weight ratio that held back heavier-than-air flight for so long.
He also claims that it is ‘a familiar fact that birds glide and soar with wings outstretched and immobile.’ As a fact, this is not at all familiar. Even though they may not be beating their wings, the wings are in fact constantly changing shape and camber to take advantage of winds and improve their aerodynamic efficiency. It is worth noting that many modern combat aircraft emulate this feat. The F 14 Tomcat has wings of variable sweep which are computer-controlled to achieve the best possible angle for any flight conditions. And the F 16 has a tilting leading edge to its wings, similarly computer-controlled, to vary the angle of attack for maximum efficiency.
He also wonders why, when men had long conquered the sea, it took them so much longer to take to the air. The answer to this must surely be painfully obvious to all but philosophers. Walk into the sea, and you stand a fair chance of floating. Walk off a cliff, and the laws of gravity bring themselves to your attention with some force. It was never a dull imagination that kept men grounded. Imagination has always soared. It was surely the lack of an appropriate technology. Once that was invented, then man began to approach the heights of his imagination.
Film Editor, Time Out, London WC2