28 November 2010

Science and engineering

There’s an important difference between science and engineering that seems often to be lost on people, especially when discussing future technology and/or the limits of scientific knowledge. The classic example that always seems to get thrown out is human flight: The scientists said we would never fly, the argument goes, and they were wrong, so take everything scientists say with a grain of salt.

Many intelligent people in the late 1800s did deny the possibility of human heavier-than-air flight. But what we tend to forget is that no scientist ever said heavier-than-air flight was physically impossible: birds do it quite routinely, a fact that was well known to these learned gentlemen. The physical principle ‒ air flow over a wing produces lift ‒ was not in question. The objection was that the engineering problems would prove insurmountable: We could not, they argued, ever engineer an aircraft light and powerful enough to fly; they were wrong only because they underestimated how good internal combustion engines would turn out to be at providing lots of power for their weight.

We go far astray when we conflate the law of physics seem to say it’s impossible and I can’t see how we’d ever make it work. Bending spoons with mental powers is in the first category; building a space elevator is in the second. For the first to work, we would have to be completely wrong about almost everything we think we know about the universe; for the second to work, we just need to have structural materials far lighter and stronger than anything we can currently make. That means that when a scientist says “spoon bending is fantasy” it’s very different than when an engineer says “space elevators are fantasy.” They said we’d never fly is a valid reply to the latter, but not to the former.

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