They are amazing craft, having functioned ten times as long as planned. Contrary to the article, neither was designed to explore the edge of the solar system. They were launched to explore the outer planets. A rare planetary alignment allowed NASA to slingshot the probes from one planet to the next... and then sling them off into the far reaches of space. Radio waves, traveling at the speed of light (it takes 8 minutes for sunlight to reach us from the star we orbit), take an entire DAY to reach the Voyagers, and another day for the return signal.