# Principle of locality and forces

I have a silly confusion about the statement written in the link Einstein and Locality

''external influence on A has no direct influence on B; this is known as the Principle of Local Action.'' Since GTR and Electromagnetism obey principle of locality. And in both cases change in A position affect the B and vice versa. Then why this contradiction come. Please correct me.

• I think electromagnetism and the GTR are both constrained by the speed of light, whereas the quantum mechanical case that does not obey the principle of locality is not (spin states change instantaneously, hence 'spooky action at a distance') Jun 6, 2014 at 12:59
• Did you mean that direct influence is the instantaneous effect $c\rightarrow\infty$. Jun 6, 2014 at 13:10
• Read about the EPR paradox.(en.wikipedia.org/wiki/EPR_paradox) I think the resolution to the paradox is during entanglement there is no information transfer or a "physical effect", and hence locality can be violated. Causality is much more fundamental than locality.
– user7757
Jun 11, 2014 at 6:17
• @ramanujan_dirac I am clear about EPR paradox and entanglement but i am concerned about the EM force and gravitational force what about them, Jun 11, 2014 at 7:32
• Quantum mechanics is local physics.stackexchange.com/q/114657. Jun 11, 2014 at 15:28