Do distant charges interact or do their fields interact?

Question

Here is my thought experiment. I know that charge is conserved quantity, but imagine that we can turn on two negative charges as some distance apart. When will they start interacting?

When each field propagates and reaches the other charge field or
when field propagates and reaches the other charge itself?

Note that, classically, electromagnetic waves do not interact with each other — Alfred Centauri, Dec 07 '20 at 16:57

score 2 · Answer 1 · answered Dec 07 '20 at 17:22

I would say option 2. The field ripples (or the propagating EM wave) are like the messengers carrying the information of the source's "existence". The messengers themselves meeting on the way means nothing. Only when the message reaches the destination, will any effect be seen. Unless any disturbance or field fluctuation reaches either of the charges, its only their own field around them which we know does nothing to themselves.

Andrew Steane · Answer 2 · 2020-12-07T21:33:17.317

1

It is option 2.

At any given event on its worldline, a given charge experiences the influences that have propagated to it from other other charges when their worldlines crossed its past light cone.

The fields, on the other hand, do not interact with one another.

edited Dec 07 '20 at 21:33

answered Dec 07 '20 at 20:21

Andrew Steane

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Do distant charges interact or do their fields interact?

2 Answers2