November 19, 2007
Engineering Is Scientific
Engineering is scientific in that it compares results to theory and adjusts accordingly. However, in engineering it is not always the theory that gets adjusted.
I was having a discussion with Gerald Browning at Climate Audit about engineering vs science. Two related but very different disciplines. Which brought up this polemic (thankfully short) from me.
In engineering it only has to work. The theory need not be correct. It just needs to bring you in the vicinity of a solution.
Second, a feed back system properly designed will cover up a lot of misunderstanding. I know the valve will be highly non-linear. Its components (O-Rings [pdf]) will have serious hysteresis and material creep problems. The gas flows will be probabilistic (see comments). You servo the system to the desired results and it doesn't matter. Which is why some of the companion articles deal with feedback and control. Instrumentation. Detectors.There is also a bit about having sufficiently large tanks inserted in the system at convenient places in order to reduce rates of change possible. It is ALL about scale. Try doubling the size of the oceans to slow down the dT/dt (rate of change of temperature with time) for a given energy input. An exercise best left to the reader.
A very bad way to do basic science. A good way to do engineering. The fact that this is engineering in service of basic science is even better.
Of course if your system response is exponential to change and your feedback loop is longer than the system response time you are farklempt. Nuclear reactors would be uncontrollable for this reason if it wasn't for the approximately 1% delayed neutrons. Even then there is a narrow range of reactivity where the delayed's help. Get above that range and the reactor self controls - i.e. melts down.
Let me add that what usually happens in these cases is that if you can get a lash-up to work and it has high utility a lot of people get assigned to understanding and improving on the original design and correcting the bad theories.
Read some of Tesla's work. Brilliant in general, but he had some serious and glaring mis-understandings - according to what we know now. The thing is his mis-understandings lead him to dead ends. OTOH he made things work. Like radio controlled boat models in the very late 1800s. An amazing accomplishment for its time.
Now it is good to have so many people studying climate. What is unfortunate is that our minuscule understanding has given rise to orthodoxy that pretends to more understanding than it actually has. This is easy to hide because the time scales are so long and the system itself is chaotic with strange attractors (You want to know the most likely weather for tomorrow? Same as today). Even when the time scales are short (electricity) understanding is some times decades in coming. The real crime in all this is not this prediction or that prediction. It is confidence intervals that do not match the quality of the data and its analysis.
One must take this as a common human failing because we see it in all fields. Predicting the future gains one prestige. Tarot reader or climate scientist. Doesn't matter.
Cross Posted at Power and Control
posted by Simon on 11.19.07 at 01:07 PM
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