HPS 0410 Einstein for Everyone Spring 2008

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Assignment 4: Origins of Special Relativity

For submission Monday Feb. 4/ Tuesday Feb. 5

Read the introduction and first two sections of Einstein's paper "On the electrodynamics of moving bodies." Read it slowly and reverently. This text is to modern physics what Genesis is to modern Christianity and the Declaration of Independence is to US history.

1. How does Einstein's opening treatment of the magnet and conductor thought experiment differ from the way the experiment is set up in the chapter, Magnet and Conductor?

2. What is the "definition of simultaneity" that Einstein describes in the first section?

For discussion in the recitation.

A. In the introduction, what is established by the magnet and conductor thought experiment? How do ether current experiments enter the discussion? What is "apparently irreconcilable" and why is it so? How is Einstein suggesting that he will solve the problem.

B. In Section 2, how does Einstein establish that observers in relative motion may disagree on the lengths of rods and the synchrony of clocks?

C. If the synchrony of different clocks is set by a definition, presumably freely chosen, then it would seem that any velocities measured by them are also a matter of freely chosen definition. So how can Einstein at the end of Section 1 say that the constancy of the speed of light is a universal constant "in agreement with experience"?