Discussion: There is no Doppler shift off a matte wheel rolling between a source and the receiver

Discussion in 'Formal debates' started by RJBeery, Nov 19, 2011.

  1. OnlyMe Valued Senior Member

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    I think I understand, but I understood the original wheel about 1200 posts and a few threads back.

    So, to know for sure we have have to wait until Tach.., responds.
     
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  3. Trippy ALEA IACTA EST Staff Member

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    If you ask me, Tach seems in imminent danger of imploding into a singularity of emo-rage.
     
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  5. RJBeery Natural Philosopher Valued Senior Member

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    I believe looking at it in terms of an infinite number of mirrors is just fine. The problem is that if the mirror's orientation is anything but zero wrt its velocity there will be a detectable Doppler shift. The only place the orientation angle is zero is at the top and bottom of the wheel, which would show no Doppler.

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    ...or perhaps this is your position as well?
     
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  7. Neddy Bate Valued Senior Member

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    I know you're not asking me, but YES! That is what everyone has been trying to explain to Tach.
     
  8. RJBeery Natural Philosopher Valued Senior Member

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    Yeah I welcome your thoughts as well Neddy Bate. I'm glad to see Tach is consistently wrong...
     
  9. Trippy ALEA IACTA EST Staff Member

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    This is my position as well - this represents the 'special case' that I have readily admitted right from my first comment on the matter.

    In the case of the mirror at the bottom of the cycle, it's because the mirror is stationary, in the case of the top of the cycle, it's because the red shift and the blue shift are equal and inverse, not because it is stationary.
     
  10. Trippy ALEA IACTA EST Staff Member

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    Heh. Yes.

    The scenario where we have a section of stainless steel pipe of zero thickness:

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    And a stainless steel washer of zero width:

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    Both of which display perfect specular reflection, and are moving between a light source and a camera, with some velocity \( v \leq \omega r\), while rotating about their C[sub]n[/sub] axis, with some angular velocity \(\omega\), oriented so that the plane containing their nC[sub]2[/sub] axes also contains the light source and the camera (or. alternatively, oriented so that the vector of motion is perpendicular to the C[sub]n[/sub] axis - same thing, different wording).

    And now that the problem has been defined unambiguously, sensible discussion of the two seperate problems, or components of the problem, can begin.
     
    Last edited: Nov 22, 2011
  11. RJBeery Natural Philosopher Valued Senior Member

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    My feeling is that no one here disagrees on anything, but perhaps I should verify:

    1. The mirrored cylinder will exhibit Doppler effects everywhere except the very special (infinitesimal) case of top/bottom
    2. The mirrored washer would exhibit Doppler effects nowhere
    3. The matte versions of either would exhibit Doppler effects everywhere except, again for very special cases
     

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