Eric Drexler likes to say: engineering is dual to science, because science tries to understand what the world does, while engineering is about getting the world to do what you want. I think we need a slightly less ‘coercive’, more ‘cooperative’ approach to the world in order to develop ‘ecotechnology’, but it’s still a useful distinction.
For example, classical mechanics is the study of what things do when they follow Newton’s laws. Control theory is the study of what you can get them to do.
Say you an upside-down pendulum on a cart. Classical mechanics says what it will do. But control theory says: if you watch the pendulum and use what you see to move the cart back and forth correctly, you can make sure the pendulum doesn’t fall over!
Control theorists do their work with the help of ‘signal-flow diagrams’. For example, here is the signal-flow diagram for…
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