The Structure of Scientific Revolutions: Thomas S Kuhn (3)

It is interesting that one hundred years after the theory of relativity came about, we are still teaching our children Newtonian mechanics, and engineers are using it to build sophisticated new airplanes and skyscrapers. Other problems, like nuclear physics and astronomy often cannot be solved without relativistic treatment. Kuhn has said that during the transition period between paradigms it is normal for such an overlap to occur. However, it seems that we have been clinging to Newton for too long for this to be the case now.

Kuhn spends considerable time wrestling with the fact that Newtonian mechanics is still so prevalent 60 years (at the time Kuhn wrote the book) after relativity replaced it.[1] I think it may be that relativity did not quite replace it. Kuhn mentions the idea that perhaps Newton’s ideas are a special case of Einstein’s ideas. After much thought, this is the school of thought I am leaning toward. There are many areas, for example, where relativity uses equations that are simply Newtonian equations with a relativistic factor thrown in. This factor is so close to “1” in traditional cases that it can be ignored. In these cases I think one could argue that Newton was not wrong, but simply incomplete. I might further argue that Newtonian mechanics really has been replaced in scientific circles and that Newtonian mechanics remains mainly as an engineering tool, because in many cases it is “close enough” and is easier to work with.[2]

A scientist would probably argue, though, that modern physics comes to its conclusions in a more scientific way than Newton did. They might argue that keeping Newtonian mechanics in use because they work in certain cases is similar to keeping the phlogiston theory because it works in certain instances.[3] Both theories originally claimed to cover all situations, but did so essentially through extrapolation. Einstein, on the other hand, [proved mathematically][4] that his theories work for all situations, and as far as we know so far, they do. We can now look back on Newton and see that he has a valid special-case theory, but this is not how it was previously presented.

Kuhn says that scientists are not attempting to solve useful problems, but simply to solve problems that are solvable. They do not set out to solve new problems. New things are discovered when the problems that should have been solvable give strange results. Newtonian physics began to yield such anomalies, and this was the crisis that bred relativity. By this way of thinking, from the purely scientific perspective, the Newtonian paradigm really has been replaced.

Perhaps one way of looking at it would be that a new paradigm comes about not because it is right, or even that more of the evidence supports it, but because it [works better].[5] On these grounds, there are certain situations where Newtonian mechanics really do work, and work better. In conventional engineering this is often the case. For example, Newtonian mechanics work far more elegantly to determine the forces required to stop a car, assuming the car was not traveling anywhere near the speed of light. For this reason, I think Newtonian mechanics are here to stay, unless a new paradigm comes about that actually makes engineering easier. Of course, there are engineering problems that only be solved with twentieth century physics, and for these problems it is very true that relativity “works better”.

Instructor's Comments:
1) Technically it is, but not conceptually
2) Many engineering applications (eg celestial navigation) are still based on ptolemaic astronomy. For those situations, it works. Would your analysis be the same for this case?
3) Ok, this is what I was hinting at
4) Means what?
5) This idea requires some definition