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B Relativity of simultaneity - missing event

  1. Feb 23, 2016 #1
    Obviously I have to learn how to start a topic, but I believed that in a scientific forum, what matters is the idea, not the presentation.
    I'll try harder this time.
    Since every scientist knows very well the ladder paradox, I believe I won't be wrong, by missing something in the set.
    ---

    A third simultaneous event is introduced in the ladder paradox, by attaching a rod to each door, which are welded perpendicularly on the inside of the doors, in a way that both rods touch when the doors are simultaneously closed (the small added red lines on the graphics)
    (The rods are not on the way of the ladder, and can be placed in a way not to touch the floor.)
    The single event "touching of the rods" verifies that both doors are closed simultaneously.
    touch - simultaneity
    no_touch - no_simultaneity
    In the same time as a single event it must be present in both frames of reference.

    As seen on the left graphic (garage frame of reference with shorter ladder), the rods touch in the frame of the garage, when the doors are closed.
    As an event, it should be present in the ladder frame of reference, but it is not.

    Here is the process of the long ladder passing through the garage as presented in Wikipedia:
    The first event is the front of the ladder approaching the exit door of the garage.
    The door closes, and then opens again to let the front of the ladder pass through. At a later time, the back of the ladder passes through the entrance door, which closes and then opens.


    See the images bellow for reference.
    ladder_garage.png
     
  2. jcsd
  3. Feb 23, 2016 #2

    Ibix

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    Again! You are treating the rods as rigid which they cannot be. How many times do we have to repeat this?

    Your diagrams are wrong because you continue to ignore the above. You either have to learn the maths and prove this for yourself (I recommend this) or take our word for it.
     
  4. Feb 23, 2016 #3

    A.T.

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    The bug rivet paradox deals with this in a simpler manner, without rotation and the other complications the OP introduces here.
    http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/bugrivet.html
     
  5. Feb 23, 2016 #4

    PAllen

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    When it seems people are quibbling about your presentation, most likely it means you have failed to get your idea across at all due to presentation issues. In may also mean (as in the series of thread you've started on the same general idea) that things you misunderstand as being inconsequential are very important to modeling the situation.
     
  6. Feb 23, 2016 #5

    Ibix

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    It's just Einstein's train, isn't it? Except instead of light pulses coming from front and rear he's got mechanical waves propagating through the rods.
     
  7. Feb 23, 2016 #6
    No, I'm not.
    I repeat my answer from the locked topic:
    note that while the end of the back door rod departs later from the point of the touch, the left rode will arrive later too, thus missing the touch, for the single fact, that the front door need to give time for the ladder to pass through.
    Also, as stated in the OP "the first event is the front of the ladder approaching the exit door of the garage.
    The door closes, and then opens again to let the front of the ladder pass through.
    At a later time, the back of the ladder passes through the entrance door, which closes and then opens."

    The above leaves no time for the touching event.

    The diagrams are not mine except for the added rods. They are widely accepted and published in Wikipedia.
    Please let us know at which point the touching event will happen.
     
  8. Feb 23, 2016 #7

    Ibix

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    Yes. You added the bit that's wrong... Try adding in the delay in the rods' movement due to the finite speed of sound in the rods.
     
  9. Feb 23, 2016 #8
    There is no rotation here.
    For your reference, here is how the rods look from closer view:
    ladder_rods.jpg
     
  10. Feb 23, 2016 #9

    Ibix

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    The rods are pointing to 3 o'clock and 9 o'clock in your first picture and to 6 o'clock in your second picture. There is rotation...
     
  11. Feb 23, 2016 #10

    Orodruin

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    You again display the same fundamental misunderstanding as before and refuse to accept correction. This thread is therefore closed. I suggest you read and try to understand the implications of the replies you have received.

    Also note that the "A" tag implies that you have a physics graduate student level understanding of the subject and expect an answer geared to that audience. It is pretty clear that you do not. Please select tags according to your level of understanding.
     
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