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Consider a charge of 1C kept a distance of $6*10^8$ m from a detector.

I find electric field due to this charge at detector.

Then, I suddenly earth that charge

and not the time it takes to be detected by detector.

It should be about 2 sec.

Has any similar experiment been performed before.

Such experiment can help to distinguish b/w speed of electromagnetic wave and speed of electric field propagation.

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    $\begingroup$ Presumably the point is to measure the propagation speed of changes in an electric field. $\endgroup$
    – John Rennie
    Commented Mar 16, 2016 at 15:38
  • $\begingroup$ @AnubhavGoel you realize this is about 50% farther than the moon is from the earth, right? $\endgroup$
    – costrom
    Commented Mar 16, 2016 at 15:57
  • $\begingroup$ @costrom Our solar system is 500000000% greater than that. We have still reached there. Such a charge can be considered near surface of earth and detector in space. $\endgroup$
    – Anubhav Goel
    Commented Mar 16, 2016 at 16:21
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    $\begingroup$ @costrom That's not a big problem though. We can rather easily measure times far shorter than seconds. $c\ \mu\text{s} \approx 300 \text{ m}$, so a scaled-down experiment is possible on Earth. $\endgroup$
    – Robin Ekman
    Commented Mar 16, 2016 at 16:41
  • $\begingroup$ @Robin Ekman I meant so much charge and distance because it would take time for charge to get earthed. $\endgroup$
    – Anubhav Goel
    Commented Mar 16, 2016 at 17:12

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This has been already studied extensively in the electrodynamics formalism of James Clerk Maxwell and experimentally proved to be correct many times. So magnetic fields and electric fields are unified into a single formalism called Electromagnetism which propagates with constant speed of light in vacuum. This means that the presence or absence of any electric and/or magnetic fields can be felt according to causality.

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  • $\begingroup$ I clearly mentioned I don't want speed of electromagnetic wave. $\endgroup$
    – Anubhav Goel
    Commented Mar 16, 2016 at 17:11
  • $\begingroup$ dear Anubhav Goel. You cannot treat E and B field separately in terms of propagation. $\endgroup$
    – Benjamin
    Commented Mar 16, 2016 at 22:06
  • $\begingroup$ Why I cannot? I can treat them different. I know they immediately follow each other. But, what if I don't consider magnetic part. My detector need not detect B. Well, Maxwell studied how fast changes in electromagnetic field are transmitted. A stationary charge does not emit any thing. It just create a field. A field like this should vanish faster than c. $\endgroup$
    – Anubhav Goel
    Commented Mar 17, 2016 at 2:48
  • $\begingroup$ A stationary (with respect to observer) charge has electric field around it all the way to infinity. Once disappeared suddenly, it will take time for the observer to notice it. It won't be simultaneous as you might think. Causality won't permit passage of information (e.g. group velocity of a packet wave) to be faster than c. $\endgroup$
    – Benjamin
    Commented Mar 17, 2016 at 3:12
  • $\begingroup$ I don't want it to be simultaneously, but faster than c. $\endgroup$
    – Anubhav Goel
    Commented Mar 17, 2016 at 3:15
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To earth the charged body does not mean that the electric field of this charges disappears.

To make such a charged body one has to separate some amount of electrons and as a result one get a negative charged body and a positive charged body side by side. So beside the weakness of the electric field of the charged body over such a big distance the angular resolution of your measurement instrument has to be very high Otherwise you will detect the overlapping fields of both charged bodies.

Of course you can separate the two charged bodies over a big distance and than start the measurement of the very weak over distance electric field. But again, to earth the body to do with the flow of the electrons from this body (or to this body) to an other body. This second body has to be out Of the area, where your instrument scan the charged body. And during the flow of the electrons due to earthing the electric field does not fall to zero immediately, especially if you had a big distance to the ground (which big distance you need to separate the field due to the possible angular resolution of your instrument.

But much more important is the fact that the electric field of charged particles are theirs intrinsic properties, means this fields could not be switched on not off. They are only separable. In mixed states of protons and electrons their fields don't vanish.

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  • $\begingroup$ The opposite charge would move to earth which has a very big radius. Also earth has almost 0 potential. So, I would easily arrange a good detecter. By, the way what about, has such experiment been performed before. Also see my last comment. $\endgroup$
    – Anubhav Goel
    Commented Mar 16, 2016 at 17:21
  • $\begingroup$ I don't care about if they would overlap, since there would always be some resolution. $\endgroup$
    – Anubhav Goel
    Commented Mar 16, 2016 at 17:22
  • $\begingroup$ I read one of your paper on , photon as particle. What does e and p stand for? $\endgroup$
    – Anubhav Goel
    Commented Mar 16, 2016 at 17:24
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    $\begingroup$ @anu You should note that none of Holger's work is peer reviewed. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Mar 16, 2016 at 17:32
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    $\begingroup$ You get peer reviewed exactly the same way someone from a university gets a peer reviewed: you submit to a journal. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Mar 16, 2016 at 19:43

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