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I know that everything that is shaped from gravity force is rotating, and gravity is a central force, but I want to know how we can understand that a black hole has an angular momentum? By which sign from the black hole? And I want to know how we can understand the electromagnetic field of a black hole, by knowing that no photon can escape from a black hole. Do photons exist in general relativity? How do we define the electric force between two electrons in general relativity? Does it have the same formula that was in classical physics? And how is this force propagated? (by photons?)

Thanks

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    $\begingroup$ Please only ask one question per post — only ask several if they are so closely related that it wouldn't make sense to split them up since they cannot reasonably be answered separately. That way, users that might be able to answer one question but not the others still can provide useful, complete answers to a question. $\endgroup$
    – Níckolas Alves
    Commented Mar 16, 2022 at 21:58
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    $\begingroup$ I am certain most of these questions recur over and over on the site and we have answers to them. Maybe search more. I'd probably suggest starting with the No Hair Theorem. $\endgroup$
    – StephenG - Help Ukraine
    Commented Mar 16, 2022 at 22:40

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In answer to your main question about how can a black hole have an electromagnetic field. I suggest that you take a look at the PBS SpaceTime video from January 27, 2022 entitled "how does gravity escape a black hole". Paraphrasing from Dr Matt O'Dowd, he said virtual particles do not really travel from one location to another carrying force with them, they are not localized in that manner. If two electrons travel close to each other they interact by the exchange of a virtual photon or more precisely they exchange the sum of all virtual photons. These photons don't follow a well-defined path between the electrons, they emerge from the electromagnetic field in the broader region occupied by both electrons. In the case of a black hole the excitation of the electromagnetic field does not emerge from the black hole and this force doesn't have to travel through the event horizon. The field surrounding the black hole is already a buzz with the virtual particles.

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  • $\begingroup$ My problem is that I don't understand what a virtual photon is,for example in the photo electric effect we can count the photons,or in case of electrostatic field if we put a dielectric ,the electrostatic field may decrease. $\endgroup$
    – user324499
    Commented Mar 19, 2022 at 14:38
  • $\begingroup$ To be honest, nobody understands what a virtual photon is. You can think of it as an excitation of the electromagnetic field. But an excitation that is not quite a photon in itself, or an electron in itself. Think of the area surrounding a bar magnet. Clearly there is energy in that area, but it is neither an electron nor a photon. This is what we refer to as virtual. Or at least the best guess. $\endgroup$
    – foolishmuse
    Commented Mar 19, 2022 at 18:03

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