Special Relativity: a Reexamination of the Second Postulate and of Space Contraction and Time Dilation

1 Special Relativity: A Reexamination of the Second Postulate and of Space Contraction and Time Dilation Paul A. Klevgard, Ph.D. Sandia National Laboratory, Ret. [email protected] Abstract Entities in physics involve either mass or energy or both. Projectiles combine both rest mass and kinetic energy (velocity). But an inertial rest mass is all mass and no kinetic energy (no velocity) whereas the photon is all kinetic energy and no (rest) mass. The inertial rest mass and the photon are therefore pure entities in that they feature, respectively, mass without kinetic energy, or kinetic energy without (rest) mass.. Pure entities may be compared at the ontological level (for form, progression in a dimension, extension in a dimension and storage). From this analysis it is shown that Einstein’s second postulate of special relativity (constant speed of light) is actually derivative from a more fundamental attribute of all pure entities. Part two of this essay focuses on the space contraction and time dilation of moving physical objects. Arguments against attributing these changes to space and time itself (Minkowski) are offered. Instead, the roles of kinetic energy and of de Broglie wave effects are presented as a better explanation. The famous twin’s paradox is discussed in an appendix. Special relativity has been with us for over a century and its predictions have been confirmed by countless experiments. Nevertheless, its conceptual and ontological foundations are not completely satisfactory. This essay will offer a critical review of two main aspects of special relativity: 1) the desirability/validity of erecting a postulate for a single phenomenon, namely the constant speed of light, and 2) the challenge of explaining why different inertial observers measure space and time differently (space contraction, time dilation). But one cannot analyze special relativity without considering the photon and the nature of radiant energy. Hence this essay will also look at how radiation energy went from quantity to entity. Part I - The Constant Speed of Light 1.0 Introduction The Scientific Revolution of the seventeenth century was mostly about mechanics and the laws of motion of material entities. Hence when scientists began to explain energy processes they naturally invoked material entities as causal agents. Three examples may be cited. The energy of combustion was at first regarded as due to the release of a material substance (philogiston). Heat itself was another assumed material substance (the caloric) that self-repelled so it would migrate from a hot object to a cold object. And, of course, in the nineteenth century radiation was regarded as a wave disturbance of the all-pervasive material aether. In the last half of the nineteenth century theories of energy became dependent upon experiments (e.g., Joules) and perhaps less speculative. Great progress was made in thermodynamics and in the kinetic theory of gasses. By 1900 all of the preceding energy theories that involved material entities were dead or on death’s door (the aether). Energy had become simply a quantitative measure in contrast with mass which was an entity with properties plus a quantitative measure. For physics in 1900, mass was an entity and energy was a quantity. But change was in the air. In December of 1900 Max Planck announced that radiation energy was quantized. That took some years to be accepted but other theoretical or experimental confirmations followed in 1905 (Einstein’s paper on the photoelectric 2 effect), 1917 (Einstein’s assertion that radiation quanta have momentum) and 1923 (Arthur Holly Compton’s experiment of X-rays losing energy when bouncing off electrons). By the mid-1920s the quantized nature of radiation could not be denied and a quantum of light was given the name “photon.” But giving a name to quantized radiation was more of a linguistic convenience than it was a conceptual change. Physicists clung to the traditional idea of energy as a quantity (not an entity) even though quantized radiation as pure energy retained its identity while traversing space just as quantized matter as pure mass retained its identity while traversing time. The outstanding physicists of the 1920s were inclined to keep as much as possible of the old ideas (energy as quantity) while still accommodating new findings. A century later we are under no similar constraints and we can explore the idea of the photon as an entity that occurs, has properties and traverses a dimension. 1.1 Looking Ahead The mathematics of special relativity has long been settled and it will not be recounted here. Our concern instead is with the nature of those entities whose properties physicists have not always examined closely. The photon and the material entity (“particle”) have obvious differences. The material entity exists, extends in space, progresses (“persists”) in time and has mass as a quantitative measure whereas the photon occurs, extends (oscillates) in time, progresses in space and has energy as a quantitative measure. But in terms of ontology they are both entities and may be compared as such. Although he didn’t characterize them as entities, Einstein compared the photon and the material particle in many of his papers with great effect.1 In the following sections we shall see that mass and (photon) energy are closely related as E = mc2 implies. Both of them extend in, and can be compressed in, one dimension only: space for mass and time (oscillation) for the photon. That is, the material entity can be squeezed in space by applying a force to it while the photon may be squeezed in time by the observer moving toward the photon source. Because extension (entity volume or duration) is confined to one dimension, we shall see that entity progression in the alternate dimension is unaffected by entity compression. Compressing inertial mass in space will not change its time progression; compressing the photon in time will not change its space progression. This insight permits a redefinition of Einstein 2nd postulate. But before this analysis can begin we must clarify our terminology. 1.2 Nomenclature The concept of quantity is straightforward. It may involve the counting of discrete units such as atoms or molecules, or it may involve measurement relative to some standard yielding a definite amount of kilograms, volts, meters or seconds. Quantitative measures may be factual but they are not physically real. Something is physically real if it has a dimensional presence (space or time) and can be said to exist or occur. For physics we may assume that only mass and energy have a dimensional presence and either exist or occur. “Field” became a protean word in twentieth century physics. It is used here in the primitive sense of something that exists and extends in space. Thus a material particle is a field (with a density measure) and so is the potential energy that surrounds a charged particle or an ion. A field is the ontological opposite of a wave: the former exists, the latter occurs. Also, the word “kinetic” means or implies patent, open or obvious; hence for physics it means “unstored.” On the other hand, the word “potential” equates to latent or hidden and hence means “stored” (e.g., potential energy is stored energy). The precise term for matter (rest mass) is “kinetic mass” since it is mass that is unstored, unhidden. In what follows the term “inertial” is shorthand for an object or system that is force-free and regarded as space-stationary for a local observer. “Entity” is also a protean word (e.g., legal entity, public entity). In the realm of physics entities must be composed of either mass or energy. Keeping a material entity in mind as a template, we can set out entity requirements. Entities must: 1) have a form which implies a dimensional presence; 2) have a quantitative measure; and 3) store their 1 In his 1905 “Heuristic” paper (on the photo-electric effect), Einstein compared the thermodynamics of the blackbody radiation gas (photons) with the enclosed molecular gas (particles) to argue for quantized radiation. He made similar comparisons between the aggregate behavior of photons and molecules in subsequent papers in 1909 and 1916/17. And while Bose applied his statistics to photons (1924), Einstein quickly saw the parallels and went on to apply these same statistics to atoms. See Martin J. Klein, “Einstein and the Wave-Particle Duality,” in Natural Philosopher, v.3, 1964. 3 opposite. For the material entity the form is that of field, the dimensional presence (extension) is space, mass is the quantitative measure and energy is what is stored. Since the 1920s physicists have treated the photon as an entity: an object of study and experimentation to ascertain its properties. The photon also meets the requirements we have set out for an entity. Photons oscillate and therefore extend in the dimension of time. They have the waveform, their quantitative measure is energy (joules) and they store their opposite, namely (relativistic) mass. 1.3 Pure Entities The photon is pure kinetic energy and is devoid of kinetic (rest) mass. The inertial massy particle or object is pure kinetic mass and is devoid of kinetic energy for a local observer. Accordingly, the photon and the inertial mass are pure entities since they do not mix mass and energy in their kinetic forms. Obviously both pure entities are quantized and they extend in a dimension. The inertial mass extends over a space interval and the photon, because of its oscillation, necessarily extends over a time interval. Both entities are also at rest and therefore located in their extension dimension.2 The inertial mass is at rest in space by its own measure and the photon is at rest in time by its own measure, time standing still at the speed of light.

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