The network-news world is quaking: ABC’s World News Tonight, with Charles Gibson, is overtaking Brian Williams on NBC’s Nightly News in the ratings after years and years of NBC domination. While New York has had our issues with ole Charlie, the achievement is nevertheless impressive. And NBC, for its part, is responding the way TV networks tend to respond: It’s firing longtime Nightly executive producer John Reiss. But infinitely more fascinating than Reiss’s imminent canning is the way Gibson is catching up. While NBC’s evening-news audience hemorrhaged over half a million viewers in 2006, ABC’s audience grew by a mere 60,000. In other words, WNT isn’t really luring eyeballs away from Nightly. It’s just that people are abandoning the format in droves, and 2006, while a fine year for ABC, was a particular crappy one at 30 Rock. So celebrate while you can in Disney world; no doubt your viewers are disappearing next. (Does Katie even have any left to lose?) Meantime, pass the Geritol.