Hi, all. There's a thought flashing through my mind yesterday. Sorry for my lack of knowledge. The thought must be something wrong. Can anyone correct it? Thanks If there is a 3000000km long power cable, and the cable is pulled to 3000000km away from the earth. A power source connected on one side A of the cable on the Earth keeps outputting the electric current, and the switch of side B on the cable (away from earth 3000000km) is close. And there's a "current detector" on the cable away from side A by 1km. Does the detector detect the current? At a specific time, if the switch of side B starts to open, does the current start to go from A simultaneously? If so, people can open and close switch of side B to let people on side A know Morse code . If the cable is 1LY long, will transmitting message to 1LY away instantly comes true?