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Usually you just learn that acceleration or deceleration of charged particles produces em radiation. But a couple of times I've read that movement of opposing charges towards or away from each other, even without acceleration, produces em radiation. Why?

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    $\begingroup$ Can you provide a link to where you have read this? I don’t believe it. Non-accelerating charges do not radiate. $\endgroup$
    – G. Smith
    Commented Apr 9, 2019 at 0:29
  • $\begingroup$ During the approach of an electron to the nucleus (protons) photons are emitted. Equal charges repeal each over without any emission of photons. I’m very interested in your source to see which other cases are mentioned. $\endgroup$ Commented Apr 9, 2019 at 4:18
  • $\begingroup$ I found an article on forbes.com called 'Ask Ethan Siegel: Why don't gravitational waves get weaker like the gravitational force does?' Midway down, he says OPPOSITE electric charges that move towards or away from each other create em radiation, but not like charges. And this is after he points out that any accelerating charge will radiate em waves..... $\endgroup$
    – Kurt Hikes
    Commented Apr 18, 2019 at 6:31

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The only reasonable explanation of the statement :

But a couple of times I've read that movement of opposing charges towards or away from each other, even without acceleration,

is that the italisized part is mistakenly attached to it.

In classical electricity and magnetism, two opposing charges without other forces acting on them will follow the Coulomb attraction of repulsion, and thus accelerate towards or away from each other. If they are not accelerating or decelerating the system is not closed and needs specific boundary conditions to be studied.

If in the realm of atoms, as the hydrogen atom where the electron does not fall on the proton by radiating, it is due to quantum mechanics , no longer classical theories hold. It is actually one of the reasons that quantum mechanics had to be postulated.

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  • $\begingroup$ If you go to forbes.com, at the Ask Ethan (Siegel) section, you will find an article called, 'Why don't gravitational waves get weaker like the gravitational force does?' Midway down, when comparing these waves to em waves, he says you can, 'take charges of opposite sign and change the distance between them' to create em waves. This sentence is after the one that says accelerating charges also create em waves. $\endgroup$
    – Kurt Hikes
    Commented Apr 18, 2019 at 5:24
  • $\begingroup$ "changing distance" is a type of acceleration. as i said, charges in space will either accelerate towards or away from each other , they cannot stays still. $\endgroup$
    – anna v
    Commented Apr 18, 2019 at 5:42
  • $\begingroup$ I realize I am a lazy idiot for not knowing how to post a direct link. And not taking the time to learn. But I am confused, because, shouldn't LIKE charges that move towards or away from each other also create em radiation? $\endgroup$
    – Kurt Hikes
    Commented Apr 18, 2019 at 6:26
  • $\begingroup$ @KurtHikes yes, any acceleration starts the process of radiation. Particularly for like charges energy has to be supplied to move towards each other because the forces are rupulsive $\endgroup$
    – anna v
    Commented Apr 18, 2019 at 7:33

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