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Relativity of simultaneity question

  1. Jan 12, 2013 #1
    i have a question about chapter 37.2 relativity of simultaneity (pearsons international edition university physics, 12th edition) .

    the text besides image b sais: inside the train, mavis moves toward the light coming from the front of the train and away from the light coming from the back of train.

    then image c shows the light from the front of the train reaching her first, in my understanding, this implies mavis sees the flashes at different times because she is moving towards the origin of one of the flashes.

    this is very confusing to me, because what i learned in the previous chapter tells me that cA' = cB' no matter how the train moves.

    Above statement is correct right?!

    if it is, then why does it look like the images are trying to tell me cA' < cB' in mavis' frame.
     
  2. jcsd
  3. Jan 12, 2013 #2

    Doc Al

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    Staff: Mentor

    The light reaches her at different times (everyone agrees with this) and she concludes that the light flashes must have happened at different times in her frame.

    Yes, the speed of light is the same in every frame. This is what forces her to conclude that the flashes were not simultaneous in her frame.

    Please explain why you think that.
     
  4. Jan 12, 2013 #3
    thank you, your response led me to seeing my mistake, i focussed so much on the arrows and waves from A' and B' that i did not see the arrows and waves from A and B, and this somehow led to my mistake.

    I no longer think the images are confusing.

    EDIT
    I got confused because A' and B' in image a are on the corners of the train, in image b they aren't, and in image c they are again on the corners of the train.
    is this a printing error?
     
    Last edited: Jan 12, 2013
  5. Jan 12, 2013 #4

    Doc Al

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    Good. :approve:

    Looks like they were a bit sloppy with the diagrams. A' and B' are the ends of the train; they should move with the train.

    I see that Mavis has moved to a different seat in diagram b. More sloppiness!
     
  6. Jan 12, 2013 #5
    yes, A' and B' are incorrectly moved the same amount of distance as mavis is.
    they are probably caused by the same printing error since they both only occur in diagram b.
     
  7. Jan 12, 2013 #6

    Doc Al

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    I'll bet you are right.
     
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