Lect09_[Compatibility_Mode]

# Lect09_[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 [email protected] TA: Dan Hartzler Office: PHYS 7 [email protected] Grader: Shuo Liu Office: PHYS 283 [email protected] 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 7 of the text. Notices: Homework is due Thursday at the beginning of your recitation ession As usual there will be a help session Tuesday in room 160 session. As usual there will be a help session Tuesday in room 160 from 1:30 to 3:30. You can ask questions and can pick up and discuss previously graded homework there.

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Question 1 n inertial observer makes measurements to determine where and when two An inertial observer makes measurements to determine where and when two events happened in her frame. She finds that the distance between the locations where they occurred is 5x10 -9 light-sec and that event 2 happened 4 nsec later than event 1. Do these events happen at the same location in some other inertial frame? A) Yes B) No C) insufficient information given to be able to tell No. This would require that observers at rest in that other frame travel at a speed greater than c relative to the original frame which is impossible. Notice that the interval between these two events is less than zero 22 2 2 2 2 2 2 21 21 21 21 21 ( ) (16 25)nsec 9nsec sc t x y z Δ= Δ Δ+ Δ = = hich we say is spacelike We saw last time that if a pair of events occur one after the other at the same location in some frame, the interval between is greater than zero, and we said hat such an interval is imelike. which we say is spacelike. ta tsu c a t e a s tee Since the interval between a given pair of events has the same value evaluated in any frame, the fact that this pair of events is separated by a negative interval means that there can be no frame in which they occur at the same location.
We showed last time that given a pair of events separated by a timelike interval, Δ s 2 > 0, there is always a frame in which they occur at the same location. An analogous statement is true for a pair of events separated by a spacelike terval, 2 < 0. Specifically, there is always a frame in which e air of interval, Δ s 0. Specifically, there is always a frame in which the pair of events separated by a spacelike interval occur at the same time.

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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.

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Lect09_[Compatibility_Mode] - Physics 344 Foundations of...

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