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Unformatted text preview: of mercury. hDp://e
duca1on.net/scien1sts/Michelson_Morley_inq.gif Expected diﬀeren1al phase shig between light traveling the longitudinal versus the transverse arms of the Michelson–Morley apparatus: 6 hDp://en.wikipedia.org/wiki/Michelson–Morley_experiment Measuring an Event • An event is something that happens, and every event can be assigned three space coordinates and one &me coordinate: 1. The Space Coordinates: We imagine the observer’s coordinate system ﬁDed with a close
packed, three
dimensional array of measuring rods, one set of rods parallel to each of the three coordinate axes. 2. The Time Coordinate: We imagine that every point of intersec1on in the array of measuring rods includes a clock. 3. The Space
&me Coordinates: The observer can now assign space
1me coordinates to an event by simply recording the 1me on the clock nearest the event and the posi1on as measured on the nearest measuring rods. hDp://
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ClocksIII.jpg 7 Simultaneity • If two observers are in rela&ve mo&on, in general, they will not agree as to whether two events are simultaneous. • If one observer ﬁnds them to be simultaneous, the other generally will not. • Simultaneity is not an absolute concept but rather a rela&ve one, depending on the mo&on of the observer. 8 Simultaneity Event A: lightning striking tree A. Event B: lightning striking tree B. Observer C: standing s1ll on lawn Observer D: siing s1ll in moving train. 9 Simultaneity hDp://www.youtube.com/watch?v=wteiuxyqtoM 10 Simultaneity: A Closer Look Suppose Sally’s train moves rightward with velocity v. (a) Event Red occurs at posi1ons RR’ and event Blue occurs at posi1ons BB’; each event sends out a wave of light. (b) Sam simultaneously detects the waves from event Red and event Blue. (c) Sally detect...
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This document was uploaded on 03/22/2014.
 Fall '14

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