A constructive approach to the special theory of relativity

Several factors make special relativity initially difficult to understand. One factor is the strongly counterintuitive nature of some of the important results, especially the relativity of simultaneity, time dilation, and length contraction. Another factor is that special relativity is usually taught, both in the classroom and textbooks, differently from other areas of physics in the undergraduate curriculum except for classical thermodynamics. That is, its results are taught as a “principle” theory and obtained by deduction from the relativity postulate and the light postulate either in the forms originally proposed or versions of them . Teaching special relativity in this way is especially problematic because unlike classical thermodynamics, which is also taught as a principle theory, the two postulates or principles for the special theory of relativity are strongly counterintuitive when taken together because the natural models of light as either an electromagnetic wave propagating in a medium the ether or a photon emitted by its source are both apparently ruled out by the relativity and the light postulates. Therefore it is unsatisfactory that it is the peculiar property of the speed of light often as it bounces about in stationary or moving railway carriages , which is relied on in many introductory treatments of special relativity to introduce students to time dilation, the relativity of simultaneity, and length contraction. In other areas of undergraduate physics, results are deduced on the basis of dynamical laws involving specific physical forces or fields. That is, the other areas are taught as “constructive” theories. As a consequence, part of the difficulty of understanding special relativity is unanswered questions such as the following: Is the contraction of the measuring rod the result of a force? and What changes inside the clock make it tick slower? Opinions differ on whether special relativity is best regarded as a principle or a constructive theory and, if the latter, as to the nature of the constructive theory. Brown argued in favor of a dynamical constructive approach, and Janssen argued in favor of a kinematical constructive theory based on the geometry of Minkowski spacetime. Norton argued that a dynamical constructive approach must fail unless an extreme form of operationalism is adopted because it requires a realist conception of spacetime from the outset. In the following, a reference to a constructive approach means a dynamical constructive approach unless otherwise indicated. Even if it is believed that it is best to approach special relativity as a principle theory and derive the results from the principles by kinematical arguments or as a kinematical constructive theory, there is common ground in most of the lit-