Timeline for Nancy Cartwright's dichotomy
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 1 at 14:22 | comment | added | Hollis Williams | I don’t think anyone is saying they are incompatible. For example, Fermi’s theory of beta decay does “explain” beta decay, but it is now seen as an effective theory of the weak interaction which is valid at low energies. | |
| Aug 21, 2023 at 6:23 | vote | accept | Mikhail Katz | ||
| Aug 6, 2023 at 11:34 | comment | added | Mikhail Katz | ... Why would looking for an explanation be incompatible with the idea that there may be stages in arriving at a satisfactory explanation? | |
| Aug 6, 2023 at 11:33 | comment | added | Mikhail Katz | Carlo, you wrote: "this distinction between a model and a theory does not resonate with me; what we seek is an explanation." I don't think this is incompatible with Cartwright's distinction. Namely, there could be several stages to an explanation. As you point out, the BCS theory derives the London equation, but the latter could have served as an explanation for the former. Somebody at a parallel site mentioned that there was a kind of model for Eistein's relativity before the general theory emerged... | |
| Jul 13, 2023 at 10:05 | comment | added | Carlo Beenakker | yes, this is accurate (although the two are intimately related: the magnetic field is "expelled" from the superconductor by an electrical current which does not decay because the resistance is zero); the point I wish to make is that the London equation describes the field expulsion by adding "by hand" an equation to the Maxwell equations of electrodynamics, without explaining where this equation comes from; the BCS theory derives the London equation, which is why for a physicist the BCS theory explains superconductivity while the London equation does not. | |
| Jul 13, 2023 at 9:51 | comment | added | Mikhail Katz | P.S. I really know nothing about this, but the point of the London-London 1935 thing seems to have been not to explain zero resistance (known since 1911), but rather to explain zero magnetic field (known only since 1933). Is this accurate? | |
| Jul 13, 2023 at 9:03 | comment | added | Mikhail Katz | I see, thanks. Is it generally thought that the London-London "model" (if you allow me to use that term) was helpful in eventually motivating the BCS theory two decades later? | |
| Jul 13, 2023 at 8:59 | comment | added | Carlo Beenakker | as a physicist, this distinction between a "model" and a "theory" does not resonate with me; what we seek is an "explanation"; the fact that a superconductor has zero resistance was known since 1911; we had to wait until 1957 for an explanation why (BCS theory); London&London in 1935 described the 1911 observations in terms of mathematical equations, without connecting these equations with established physical foundations; their equations "came out of the blue"; this is why their work is not considered an explanation of superconductivity. | |
| Jul 13, 2023 at 8:49 | comment | added | Mikhail Katz | Is it correct to describe Cartwright's insight as follows? London and London developed a phenomenological model of superconductivity. Eventually (two decades later?), what is considered a proper theoretical explanation at the molecular level was developed. However, Cartwright stresses the importance of the model, and notes that sometimes the significance of models is not sufficiently appreciated when people think of theory as explaining the phenomena directly. ?? | |
| Jul 6, 2023 at 19:21 | history | answered | Carlo Beenakker | CC BY-SA 4.0 |