Lect13_[Compatibility_Mode]

Lect13_[Compatibility_Mode] - Physics 344 Foundations of...

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Physics 344 Foundations of 21 st Century Physics: Relativity, Quantum Mechanics and heir Applications Their Applications Instructor: Dr. Mark Haugan Office: PHYS 282 haugan@purdue.edu TA: Dan Hartzler Office: PHYS 7 dhartzle@purdue.edu Grader: Shuo Liu Office: PHYS 283 liu305@purdue.edu Office Hours: If you have questions, just email us to make an ppointment. e enjoy talking about physics! appointment. We enjoy talking about physics! Reading: Chapter 9 of the text. Notices: Homework is due at the beginning of your Thursday recitation ession session. Exam I will be at 8:00pm Thursday, October 7 in MTHW 210
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Proper Time We have been getting used to the fact that special relativity forces us to be careful when discussing time intervals measured by inertial observers (coordinate time intervals) because observers in relative motion can measure different time lapses between any given pair of events. On the other hand, we have seen that there is always an inertial frame in which a pair of events with a timelike separation happen at the same location, and that a measurement of the time that elapses between the occurrence of the events is measured by an observer at rest at that location in that frame in a particularly direct way. It is so direct, in fact, that it has an invariant meaning. Observers in any inertial frame agree on its value. The inertial observer who happens to be at the location at which both events occur simply counts off the number of ticks their lock makes between the occurrences of the events. Any observer in any clock makes between the occurrences of the events. Any observer in any frame watching the process will agree on the number of ticks counted. Since these other observers also agree on the rate at which a clock identical to the one used ticks when at rest in their own frame, they are able to turn the number of ticks observed into a time interval that every observer agrees on. We call it the proper time interval measured by the particular observer whose location coincided with the location of both events when they happened.
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When, as in the case just considered, the observer measuring the proper me interval is an inertial observer the invariant result they obtain is time interval is an inertial observer, the invariant result they obtain is THE invariant interval between the pair of events. Proper time intervals measured by non-inertial observers also have a frame- dependent (invariant) significance as long as the ticking rate of the clock As the example we worked through in our clicker questions last time suggested, independent (invariant) significance as long as the ticking rate of the clock they use to measure it is not significantly affected by their acceleration. observers who travel different worldlines between a pair of events A and B measure different proper time intervals to elapse etween them t t’ between them.
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This note was uploaded on 11/26/2010 for the course PHYS 344 taught by Professor Garfinkel during the Spring '08 term at Purdue University-West Lafayette.

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Lect13_[Compatibility_Mode] - Physics 344 Foundations of...

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