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Lecture Four

Lecture Four. Attempts to Save Ether Hypothesis. Status. Michelson-Morley experiment shows null result. Attempts to Save Ether before Special Relativity. Contraction Hypothesis Ether-Drag Hypothesis Modify Electrodynamics. Contraction Hypothesis. Fitzgeral (1892) Lorentz

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Lecture Four

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  1. Lecture Four

  2. Attempts to Save Ether Hypothesis

  3. Status Michelson-Morley experiment shows null result.

  4. Attempts to Save Etherbefore Special Relativity • Contraction Hypothesis • Ether-Drag Hypothesis • Modify Electrodynamics

  5. Contraction Hypothesis • Fitzgeral(1892) • Lorentz Length is contracted in the direction of motion.

  6. DemolishedbyKennedy-Thorndikeexperiment (1932)

  7. Ether-Drag Hypothesis contradicted with • Stellar aberration (Bradley 1727) • Fizeau convection coefficient (Fresnel 1817, Fizeau 1857)

  8. Stellar Aberration

  9. Stellar Aberration

  10. Stellar Aberration

  11. Fizeau Experiment

  12. Fizeau Experiment velocity of light v in a medium of refractive index n moving with a velocity vw

  13. Modify Electrodynamics Emission Theories The velocity of a light wave is connected with the motion of the source rather than with an ether.

  14. Modify Electrodynamics Emission Theories • The velocity of light is c relative to the original source. • This velocity is independent of the state of the medium transmitting the light.

  15. Emission Theories are contradicted with • de Sitter observations on binary stars • Michelson-Morley experiment using extraterrestrial light source

  16. Conclusions • The speed of light is the same in all inertial systems, independent of the relative motion of source and observer. • A relativity principle applicable both to mechanics and to electrodynamics.

  17. Conclusions • Galilean transformations must be replaced. • The laws of mechanics which were consistent with Galilean transformations needs to be modified.

  18. Special Relativity Einstein 1905 “On the Electrodynamics of Moving Bodies”

  19. Two Postulates • Principle of Relativity • Principle of Constancy of Speed of Light

  20. Principle of Relativity • include alllaws of physics • no measurements to designate an inertial system as intrinsically stationary or moving

  21. Principle of Relativity • no experiment entirely within an inertial system can tell the motion with respect to any other.

  22. Principle of Constancyof Speed of Light • consistent with Michelson-Morley experiment

  23. Experimental Basis

  24. Program of the Theory • nature of time • transformation keeping velocity of light constant • Lorentz transformation

  25. Einstein • In his early life none of his “elders” recognized his genius. • Until almost thirty he had never seen a real theoretical physicists, “except in the mirror!”

  26. Einstein • statistical mechanics • atomic nature of matter • special relativity • principle of equivalence • light quanta hypothesis • specific heat of solids

  27. Einstein 1905 • Quantum theory of light • Brownian motion • Special Relativity

  28. Einstein • not in the mainstream • nature of time • abandoned Newton’s universal time

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