PDA

View Full Version : Thomas Kuhn Paradigm Shifts? Or Supersets?



lpetrich
2002-Jun-02, 06:35 AM
Ever since Thomas Kuhn published The Structure of Scientific Revolutions, "paradigm shifts" have been a beloved concept of advocates of various heretical theories -- theories that presumably require only a paradigm shift to accept.

But have there been real paradigm shifts in the history of science? I believe that several of them have been the development of superset paradigms -- paradims that include older paradigms essentially intact as special cases.

The rise of Newtonian mechanics IMO was a true paradigm shift; most earlier theorizing could not be fit into it very well, at least to the extent that it could be called well-defined theorizing. For example, IIRC Aristotle had believed that the elements have a natural layering: earth, water, air, fire, and ether (the substance of the heavens), which accounts for which way different objects move (rocks go downward through water; both go downward through air; fire goes upward through air). However, Newtonian mechanics features a drastically different explanation: due to the force of gravity, higher-density objects are pulled down more than lower-density objects, making them sink.

By comparison, the paradigms of relativity and quantum mechanics are essentially supersets of Newtonian mechanics; they share many of its concepts, and they essentially become Newtonian mechanics in some simple limiting cases.

Another true paradigm shift was the reinterpretation of chemical elements from the Greek earth, air, fire, and water to the present conception of them in the 18th cy., notably by Lavoisier. By comparison, the valence-bond theory and the Periodic Table of Elements were essentially superset paradigms. And all these become subsets of quantum mechanics in an emergent-property sense.

Consider a pile of sand vs. its individual grains -- being shaped like a pile is a property that none of the individual grains have, but that they collectively have. Also, it's possible to calculate the behavior of this sandpile from the behavior of all of its individual sand grains, at least if one has a big enough computer. But the sandpile can be viewed as having its own special properties, like its ability to flow, be mixed with water, and be easily reshaped.

In geology, the recognition of the geological column in the early 19th cy. was a true paradigm shift; before that, theorizing on the Earth's history was little better than hand-waving. Likewise, the recognition of continental drift in the 1960's was a true paradigm shift. Before it was widely accepted, the origin of mountains, for example, was the source of endless controversy, while after it, most mountains were easily explainable as side effects of continental drift.

In biology, Darwin's publication of The Origin of Species triggered a true paradigm shift in biology. Though the idea of descent with modification was far from original with him, he elevated it from a vague speculation to the solution of a host of biological riddles.

Likewise, Mendelian genetics was a big paradigm shift, leaving behind earlier theorizing and folklore.

However, molecular biology has been a superset paradigm, though with larger-scale biological features being subsets in an emergent-property sense.

So I think that we ought to be suspicious of those who brag that their theories are big paradigm shifts -- it's like calling oneself a persecuted Galileo.

John Kierein
2002-Jun-02, 11:18 AM
However, Newtonian mechanics features a drastically different explanation: due to the force of gravity, higher-density objects are pulled down more than lower-density objects, making them sink.
I thought Galileo showed that all objects fall at the same speed; I.E., higher density objects are pulled down the same as as lower density objects. I think it was Archimedes who said Eureka!
This link sounds like a bunch of philosophical gobbledegook. You can't tell what's "right" from looking at "paradigm shifts". Instead you have use observation and test with an open mind.

GrapesOfWrath
2002-Jun-02, 03:31 PM
On 2002-06-02 02:35, lpetrich wrote:
By comparison, the paradigms of relativity and quantum mechanics are essentially supersets of Newtonian mechanics; they share many of its concepts, and they essentially become Newtonian mechanics in some simple limiting cases.

I think it's going to take a paradigm shift before we realize that relativity and quantum mechanics are not even close to the same as Newtonian mechanics--and we won't make much progress until that occurs. In other words, we're in the midst of a paradigm shift that started a hundred years ago.

Espritch
2002-Jun-02, 03:49 PM
I thought Galileo showed that all objects fall at the same speed; I.E., higher density objects are pulled down the same as as lower density objects.

I though what he demonstrated was that higher and lower density object are accelerated by gravity at the same rate. This does not indicate they are "pulled down the same". Equal accelaration for objects of different mass requires a different amount of force being applied.

Your selection of this particular topic in your response (I assume) relates to your contention that we need a "paradigm shift" to view gravity as a push. Given that the Newtonian model of gravity seems to account well for observed orbital mechanics and has allowed us to land men on the moon, put landers on Mars, and send probes to the far reaches of the solar system, is there any oberservational evidence you can point to that would seem to require such a paradigm shift? Just curious.

John Kierein
2002-Jun-02, 09:49 PM
Pushing gravity is a return to Newtonian gravity. There is an interesting discussion of the history of pushing gravity in the book "Pushing Gravity" and how it is in agreement with Newton. Early proponents were Lesage and a Newton protege, Fatio, and the idea was revived by Kelvin. One of the later proponents was Charles Brush. Newton himself was supportive of the idea for quite a while, although he really had no idea what caused gravity. But he described the force very successfully. My personal opinion is that General Relativity does not give a reason for gravity, but just is an attempt to describe it better than Newton. As a matter of fact, I don't necessarily agree with Einstein that light would act the same in a gravitational field as it would in an accelerating frame of reference unless the "push" acts on photons as well as on on massive objects. I have yet to see where there is good independent evidence that this happens.