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B Is it possible to create macroscopic Casimir effect?

  1. Aug 1, 2016 #1
    Hello.
    I read a lot about Casimir Effect. It creates attractive (or repulsive)force between two metal, parallel, electrically neutral, conducting plates. It causes that between plates, it is less electromagnetic field fluctuation wavelength than outside (vacuum). Logic tells me that if vacuum energy is zero-point energy that energy between casimir plates must be NEGATIVE! I also read that casimir effect is measurable if the gap between plates is less than 7-5 nanometers. Is it possible to operate casimir effect on macroscopic scale, say a few centimeters, meter?
     
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  3. Aug 1, 2016 #2

    mfb

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    The energy scale is arbitrary if we leave out gravity. It is convenient to set the energy density of the vacuum to zero, but it is not necessary. If you do it, you get negative energy densities between the plates.
    You have it at any scale, but for a distance of more than a few nanometers it is completely negligible.
     
  4. Aug 1, 2016 #3
    Is it possible that the Casimir force on a macroscopic scale was the same as in the microscopic scale? Maybe by controlling electromagnetic field?
     
  5. Aug 1, 2016 #4

    mfb

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    You try to make categories that do not exist. For parallel plates at distance d and area A, the force is$$F=\frac{\pi^2 \hbar c}{240} \frac{A}{d^4}$$
    Plug in A = 1 mm2 and d = 5 nm and you get 2 N - a measurable force. Plug in A = 1 m2 and d = 10 cm, and you get 1.3*10-23 N - completely negligible. It is exactly the same effect described by the same formula, but on larger scales it is negligible.
     
    Last edited: Aug 1, 2016
  6. Aug 1, 2016 #5
    Hey @mfb, shouldn't the distance be to the 4th power, not the area?
     
  7. Aug 1, 2016 #6

    mfb

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    Oops, typo. LaTeX tried to put the whole fraction to the 4th power.
     
  8. Aug 1, 2016 #7

    Vanadium 50

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    Bad LaTex! Bad, naughty LaTeX!

    If it helps, remember the Casimir force is a pressure. F needs to be proportional to A. (And in natural units, pressure has units of r-4, so that gives you your d dependence)
     
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