Any civilization interplanetary communications will come upon an annoying lag, for no matter how the scientists and technicians improve their technology, they cannot come up with a method of making light travel faster than light. The light-lag between say Earth and the moon is only a second or two; but what happens when a planet as distant as Pluto were colonized, as it eventually will be? How can one conduct a conversation between two parties when you have to wait hours between question and reply?