Experimentation on Analogue Models

Summary 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

Physically Similar Systems - A History of the Concept

PreprintThe 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

Plasmando una visión fragmentada: "Obabakoak" como ciclo de cuentos

El artículo primero esboza una reseña del "ciclo de cuentos" como género narrativo: cada relato es independiente y al mismo tiempo se relaciona con el resto para crear un mundo literario más complejo. En "Obabakoak", de Bernardo Atxaga, se plantea esta consigna como desafío: el lector debe –al igual que los personajes– interrelacionar los fragmentos para descubrir un significado misterioso, oculto tras un mundo de apariencias. The article first sketches an outline of the “cycle of stories” as a narrative genre: each account is independent and at the same time related with the rest in order to create a more complete literary world. In "Obabakoak", by Bernardo Atxaga, this order is considered a challenge: the reader should—equal to the characters—interrelate the fragments in order to discover a mysterious, occult universe through a world of appearances

The Morals of Model-Making

I address questions about values in model-making in engineering, specifically: Might the role of values be attributable solely to interests involved in specifying and using the model? Selected examples illustrate the surprisingly wide variety of things one must take into account in the model-making itself. The notions of system (as used in engineering thermodynamics), and physically similar systems (as used in the physical sciences) are important and powerful in determining what is relevant to an engineering model. Another example (windfarms) illustrates how an idea to completely re-characterize, or reframe, an engineering problem arose during model-making. I employ a qualitative analogue of the notion of physically similar systems. Historical cases can thus be drawn upon; I illustrate with a comparison between a geoengineering proposal to inject, or spray, sulfate aerosols, and two different historical cases involving the spraying of DDT (fire ant eradication; malaria eradication). The current geoengineering proposal is seen to be like the disastrous and counterproductive case, and unlike the successful case, of the spraying of DDT. I conclude by explaining my view that model-making in science is analogous to moral perception in action, drawing on a view in moral theory that has come to be called moral particularism

Limited acute CTL escape among three founder viruses in a case of acute heterosexual transmission of HIV-1 infections

New genome sequencing techniques have suggested that productive HIV-infection arises from a single founder virus in 80% of heterosexual transmissions. Viral adaptation to early HLA-restricted CTL responses has been described in several cases of acute infection. Here, we describe immunological and virological data from a case who presented in Fiebig stage II clade A HIV-infection, five days after an epidemiologically proven non-consensual sexual transmission

Models and representation

The problem of representation has generated a sizable literature, which has been growing fast in particular over the last decade. The aim of this chapter is to review this body of work and assess the strengths and weaknesses of the different proposals