You remember how people went about trying to achieve powered flight. They didn't begin with an understanding of the laws of aerodynamics. They didn't begin with a theory based on research and carefully planned experimentation. They just built contraptions, pushed them off the sides of cliffs, and hoped for the best.
All right. I want to follow one of those early trials in detail. Let's suppose that this trial is being made in one of those wonderful pedal-driven contraptions with flapping wings, based on a mistaken understanding of avian flight.
As the flight begins, all is well. Our would-be airman has been pushed off the edge of the cliff and is pedaling away, and the wings of his craft are flapping like crazy. He's feeling wonderful, ecstatic. He's experiencing the freedom of the air. What he doesn't realize, however, is that this craft is aerodynamically incapable of flight. It simply isn't in compliance with the laws that make flight possible-but he would laugh if you told him this. He's never heard of such laws, knows nothing about them. He would point at those flapping wings and say, `See? Just like a bird!' Nevertheless, whatever he thinks, he's not in flight. He's an unsupported object falling toward the center of the earth. He's not in flight, he's in free fall. Are you with me so far?
Fortunately-or, rather, unfortunately for our airman-he chose a very high cliff to launch his craft from. His disillusionment is a long way off in time and space. There he is in free fall, feeling wonderful and congratulating himself on his triumph He's like the man in the joke who jumps out of a ninetieth-floor window on a bet. As he passes the tenth floor, he says to himself, `Well, so far so good!
There he is in free fall, experiencing the exhilaration of what he takes to be flight. From his great height he can see for miles around, and one thing he sees puzzles him: The floor of the valley is dotted with craft just like his-not crashed, simply abandoned. `Why,' he wonders, aren't these craft in the air instead of sitting on the ground? What sort of fools would abandon their aircraft when they could be enjoying the freedom of the air?' Ah well, the behavioral quirks of less talented, earthbound mortals are none of his concern. However, looking down into the valley has brought something else to his attention. He doesn't seem to be maintaining his altitude. In fact, the earth seems to be rising up toward him. Well, he's not very worried about that. After all, his flight has been a complete success up to now, and there's no reason why it shouldn't go on being a success. He just has to pedal a little harder, that's all.
So far so good. He thinks with amusement of those predicted that his flight would end in disaster, broken bones, and death. Here he is, he's come all this way, and he hasn't even gotten a bruise, much less a broken bone. But then he looks down again, and what he sees really disturbs him. The law of gravity is catching up to him at the rate of thirty-two feet per second per second-at an accelerating rate. The ground is now rushing up toward him in an alarming way. He's disturbed but far from desperate. `My craft has brought me this far in safety,' he tells himself. I just have to keep going.' And so he starts pedaling with all his might. Which of course does him no good at all, because his craft simply isn't in accord with the laws of aerodynamics. Even if he had the power of a thousand men in his legs-ten thousand, a million-that craft is not going to achieve flight. That craft is doomed-and so is he unless he abandons it.
"Right. I see what you're saying, but I don't see the connection with what we're talking about here."