Introducing Special RelativityEinsteinPrehistoryPostulates of Special RelativityMinkowski spacetimeBasicsGeometry of Minkowski spacetimeOddities of SRTime dilationLength contractionTwin paradoxIntroducing Special RelativityMinkowski spacetimeOddities of SRSpecial RelativityChristian Wüthrichhttp://philosophy.ucsd.edu/faculty/wuthrich/146 Philosophy of PhysicsClass 16, 20 November 2007Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special RelativityAlbert Einstein (1879-1955)German-born Swiss-American physicistAnnus mirabilis 1905special and general relativity, photoelectriceffect, contributions to statistical mechanics,quantum theory, early advocate of atomic thy1921 Nobel Prize in Physics “for his services toTheoretical Physics, and especially for hisdiscovery of the law of the photoelectric effect”Einstein-Hilbert action, Bose-Einsteinstatistics, Einstein field equations,Einstein-Poincaré synchronisation, Einsteinnotation, Einstein tensor,Einstein-Podolsky-Rosen paradox, EinsteinrefrigeratorChristian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special RelativityAlbert Einstein’s famous 1905 article“On the Electrodynamics of Moving Bodies”, Annalen der Physik 17: 891-921“It is known that Maxwell’s electrodynamics—as usually understoodat the present time—when applied to moving bodies, leads toasymmetries which do not appear to be inherent in the phenomena.Take, for example, the reciprocal electrodynamic action of a magnetand a conductor. The observable phenomenon here depends only onthe relative motion of the conductor and the magnet, whereas thecustomary view draws a sharp distinction between the two cases inwhich either the one or the other of these bodies is in motion. For ifthe magnet is in motion and the conductor at rest, there arises in theneighbourhood of the magnet an electric field with a certain definiteenergy, producing a current at the places where parts of theconductor are situated. But if the magnet is stationary and theconductor in motion, no electric field arises in the neighbourhood ofthe magnet...Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special Relativity“In the conductor, however, we find an electromotive force, to which initself there is no corresponding energy, but which givesrise–assuming equality of relative motion in the two casesdiscussed–to electric currents of the same path and intensity asthose produced by the electric forces in the former case.Examples of this sort, together with the unsuccessful attempts todiscover any motion of the earth relatively to the “light medium,”suggest that the phenomena of electrodynamics as well as ofmechanics possess no properties corresponding to the idea ofabsolute rest. They suggest rather that, as has already been shownto the first order of small quantities, the same laws of electrodynamicsand optics will be valid for all frames of reference for which theequations of mechanics hold good...Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special Relativity“We will raise this conjecture (the purport of which will hereafter becalled the “Principle of Relativity”) to the status of a postulate, andalso introduce another postulate, which is only apparentlyirreconcilable with the former, namely, that light is always propagatedin empty space with a definite velocity c which is independent of thestate of motion of the emitting body. These two postulates suffice forthe attainment of a simple and consistent theory of theelectrodynamics of moving bodies based on Maxwell’s theory forstationary bodies. The introduction of a “luminiferous aether” willprove to be superfluous inasmuch as the view here to be developedwill not require an “absolutely stationary space” provided with specialproperties, nor assign a velocity-vector to a point of the empty spacein which electromagnetic processes take place...Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special Relativity“The theory to be developed is based–like all electrodynamics–on thekinematics of the rigid body, since the assertions of any such theoryhave to do with the relationships between rigid bodies (systems ofco-ordinates), clocks, and electromagnetic processes. Insufficientconsideration of this circumstance lies at the root of the difficultieswhich the electrodynamics of moving bodies at present encounters.”Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special RelativityOrigins: James Clerk Maxwell (1831-1879)English physicistdynamical thy of electromagnetismlight as electromagnetic wave, withdeterminate velocity of propagation⇒ as wave, velocity of propagation of light shouldbe same in all directions and independent ofmotion of source relative to observerbut: this velocity is not independent of velocityof observer (sound waves and pilot example)but what’s the medium through which thes ewaves propagated?⇒ aether: invisible, but all-pervasive medium , atabsolute rest⇒ possibility to experimentally distinguishabsolute motion from absolute restChristian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special RelativityMichelson-Morley experiment (1881/87)Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special RelativityThe Postulates of Special Relativity (SR)1Relativity Principle: “The same laws of electrodynamicsand optics will be valid for all frames of reference for whichthe equations of mechanics hold good [= inertial frames].”(Einstein (1905), 891)2Light Postulate: “Light propagates through empty spacewith a definite velocity which is independent of the state ofmotion of the emitting body.” (ibid)3(Space and time are isotropic and homogeneous.)Michel Janssen (2007). “Appendix A: Special Relativity”. Forthcoming in hisedited Cambridge Companion to Einstein. Cambridge University Press.Christian Wüthrich Class 16Introducing Special RelativityMinkowski spacetimeOddities of SREinsteinPrehistoryPostulates of Special