Comments on: “What?” Said the Chinchilla

By: PCP

PCP — Sat, 05 Dec 2009 23:50:03 +0000

Sound stimuli,
Saltatory chinchillas!
Settled science
Or unsound software?
So what, $zillions unspent.

By: malthus

malthus — Sat, 05 Dec 2009 17:39:06 +0000

One horror story that went around the aerospace programming community in the 80s was that a fly-by-wire fighter unexpectedly flipped upside-down upon crossing the Equator for the first time, presumably because the latitude went negative.

This illustrates that it is just as important to spend as much time and funds on testing as on the object program. Then of course, the test software needs to be well-written and tested, which can lead to a never-ending process and, thank Darwin, employ a lot of us programmers.

By: NedLudd

NedLudd — Sat, 05 Dec 2009 01:38:27 +0000

One of my previous jobs involved developing a portable process control system to be used to demonstrate the feasibility of computer control for chemical processes. The first job we tried it on was a fiber spinning plant. We collected the data and gave it to a Chem. Engineer with computer experience who was to model the chemical process. After a period of time that person was ready to display the results of their model. I was greatly dismayed when that engineer blithely displayed a graph of real data from the data gathered with the results of the model. At the first major excursion, the model went in the opposite direction from reality. None of the Chem. Engineers questioned this. That was one of my signals to look for other employment.

Reality trumps computer models.

By: Shannon Love

Shannon Love — Fri, 04 Dec 2009 20:55:16 +0000

Class Of 71 Alum,

Yes, using the data used to create a model to test a models predictions runs the risk of creating a “fitted” model. In a fitted model, mathematical relationships creep in that do not represent natural process but just mathematical means of reproducing the data used to create the model.

By: class of 71 alum

class of 71 alum — Fri, 04 Dec 2009 20:27:54 +0000

While the quality of the code and the software development process at CRU is horrendous the problems with the climate models do not stop there. Even if the code was perfect the climate scientists input assumptions that bias their models towards a preordained conclusion (warming). Their assumptions in terms of a feedback effect for the increased CO2 levels are now being shown to be in error by R. Lindzen of MIT.

And the climate modelers seem unaware that models of complex phenomena must be tested extensively on out of sample data (i.e. data not used in constructing the models themselves)before they have any validity as inputs into decision making. When they are tested on “new” data they have failed miserably to correctly predict temperature level.

This whole climate science area is beginning to make me think of Lysenkoism, phrenology, Piltdown Man, etc. as analogies to it.

By: Michael Kennedy

Michael Kennedy — Fri, 04 Dec 2009 18:33:47 +0000

When I worked at the Douglas Aircraft Company wind tunnel in El Segundo, back in the dark ages, we had a very practical demonstration of the power of a single plus/minus sign. We would get projects to test. We had had nothing to do with the development and were dependent on the engineers that designed the device for its behavior. One day, when I was fortunately away, the guys got a new design for the cowl of a jet engine nacelle. It had a bulb shaped central cone, sort of like a spinner but it was not attached to the compressor shaft. It was mounted in the intake on rather thin struts. The model was put in the four foot wind tunnel and mounted in the plenum chamber. There was a quartz window for the camera to take Schlieren photos during the run. Well the big butterfly valve was opened and, as the wind velocity approached Mach I, the wind tunnel staff who were watching were horrified to see the bulb device break loose of its struts and go UP THE TUNNEL AGAINST THE FLOW ! Everybody yelled a warning and guys grabbed onto the steel columns that held up the roof. About ten seconds later, the bulb came back down the tunnel at Mach I, hit the quartz window and broke it, and the tunnel decompressed into the building. Fortunately, this had been anticipated and the roof was mounted on tracks that allowed it to lift about a foot. Needless to say, they had about 400 miles an hour of wind for a couple of seconds there. Major damage was limited and nobody got blown away as it dissipated in a couple of seconds but it was exciting. I later heard that when the engineers went over the calculations, they found a plus sign swapped for a minus.