Philosophy of Science
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Item Physically similar systems: A history of the concept(Springer, 2017) Sterrett, Susan G.The concept of similar systems arose in physics, and appears to have originated with Newton in the seventeenth century. This chapter provides a critical history of the concept of physically similar systems, the twentieth century concept into which it developed. The concept was used in the nineteenth century in various fields of engineering (Froude, Bertrand, Reech), theoretical physics (van der Waals, Onnes, Lorentz, Maxwell, Boltzmann) and theoretical and experimental hydrodynamics (Stokes, Helmholtz, Reynolds, Prandtl, Rayleigh). In 1914, it was articulated in terms of ideas developed in the eighteenth century and used in nineteenth century mathematics and mechanics: equations, functions and dimensional analysis. The terminology physically similar systems was proposed for this new characterization of similar systems by the physicist Edgar Buckingham. Related work by Vaschy, Bertrand, and Riabouchinsky had appeared by then. The concept is very powerful in studying physical phenomena both theoretically and experimentally. As it is not currently part of the core curricula of STEM disciplines or philosophy of science, it is not as well known as it ought to be.Item Experimentation on analogue models(2015-05-31) Sterrett, Susan G.Analogue models are actual physical setups used to model something else. They are especially useful when what we wish to investigate is difficult to observe or experiment upon due to size or distance in space or time: for example, if the thing we wish to investigate is too large, too far away, takes place on a time scale that is too long, does not yet exist or has ceased to exist. The range and variety of analogue models is too extensive to attempt a survey. In this article, I describe and discuss several different analogue model experiments, the results of those model experiments, and the basis for constructing them and interpreting their results. Examples of analogue models for surface waves in lakes, for earthquakes and volcanoes in geophysics, and for black holes in general relativity, are described, with a focus on examining the bases for claims that these analogues are appropriate analogues of what they are used to investigate. A table showing three different kinds of bases for reasoning using analogue models is provided. Finally, it is shown how the examples in this article counter three common misconceptions about the use of analogue models in physics.Item Kinds of models(2003-03-20) Sterrett, Susan G.In this paper, I survey a broad variety of models with an eye to asking what kind of model each is in the following sense: in virtue of what is each of them regarded as a model? It will be seen that when we classify models according to the answer to this question, it comes to light that the notion of model predominant in philosophy of science covers only some of the kinds of models used in scientific contexts. The notion of a model predominant in philosophy of science requires that a model be related to some thing formal, such as equations or statements. Not all the examples provided in the brief survey in this paper fit that notion of a model. I identify another kind of model that ought to be taken more seriously in philosophical and foundational studies of scientific models, which I call a “piece of the world” kind of model, to contrast with a “realm of thought” kind of model.Item Similarity and dimensional analysis(Elsevier/North-Holland, 2009) Sterrett, Susan G.The importance of similarity in comprehending things and reasoning about them was recognized before the time of Plato. Similarity continues to be important in philosophy, science, and technology to this day. The historical roots of the concepts of similarity, ratio and proportion will be accorded a brief mention in this article order to provide a fuller understanding of the relationship between dimensionless parameters and reasoning from similarity. The main topic of this article, however, is the use of dimensional analysis in similarity-based reasoning in current contexts.Item Physical models and fundamental laws: Using one piece of the world to tell about another(Springer-Verlag, 2002-03-01) Sterrett, Susan G.In this paper I discuss the relationship between model, theories, and laws in the practice of experimental scale modeling. The methodology of experimental scale modeling, also known as physical similarity, differs markedly from that of other kinds of models in ways that are important to issues in philosophy of science. In this paper, I examine how scale models are used in making inferences. The main question I address is "How are fundamental laws involved in the construction of and inferences drawn from, experimental scale models?" I propose there is a refreshing alter- native to the mainstream view that models can serve only as intermediaries between theory and exPeriment. Using the methodology of scale models, one can use observations on one piece of the worm to make inferences about another piece of the world, without involving an intermediate abstract model about which one reasons. The philosophical significance of that point to philosophy of science is that the method of physical similarity, which provides the basis for inferences based upon scale models, is a qualitatively different way in which fundamental laws can be used in analogical reasoning that is truly informative. Finally, as this method provides a formal basis for case-based reasoning, it may be helpful in formalizing methods used in some of the so-called "special sciences".