# How fast is electrostatic force? [closed]

Suppose we have a charge $$Q$$ in deep space (isolated), now suppose another charge $$q$$ appears instantly (no matter how). Obviously it will feel electrostatic force but the question is how quickly (will the be felt instantly even at large distance). As I mentioned electrostatic, both the charge are stationary

• I'm closing this post (v2) as non-mainstream as a charge $q$ cannot appear instantly. – Qmechanic Apr 25 at 20:13
• But it is a reasonable thought experiment? And I'd say reasonable for the concept of the propogation of EM radiation. – SamuraiMelon Apr 25 at 21:43

The 2nd charge $$q$$ will be felt (by $$Q$$) after a time $$t$$ such that $$t=\frac{d}{c} \tag{1}$$ Where $$d$$ is the distance between the charges and $$c$$ is the speed of light in a vacuum.
The effects of $$Q$$ on $$q$$ should be felt instantly (given $$Q$$ was already present for a sufficient time still given by (1)).
• @Rob But the first charge $Q$ won't feel the effects of the second charge $q$ till a time $\frac{d}{c}$? Perhaps I should edit the answer to make it clearer which charge I'm referring to feeling an effect. – SamuraiMelon Apr 28 at 12:14