My book says:
"At each electrode-electrolyte interface there is a tendency of metal ions from the solution to deposit on the metal electrode trying to make it positively charged. At the same time, metal atoms of the electrode have a tendency to go into the solution as ions and leave behind the electrons at the electrode trying to make it negatively charged. At equilibrium, there is a separation of charges and depending on the tendencies of the two opposing reactions, the electrode may be positively or negatively charged with respect to the solution. A potential difference develops between the electrode and the electrolyte which is called electrode potential."
My doubt is whether electrode potential develops after we connect the reduction and oxidation half cells or it develops as soon as we dip the metal in the solution of it's electrolyte before connecting it to other half cell? And if the electrode potential develops before connecting it to the other half cell why can't we measure the absolute potential difference(without using standard hydrogen electrode as reference)?