"Course," Kurt said. He dug out his laptop, a battered thing held together with band stickers and gaffer tape, and plugged in a wireless card. The others started to pass him back his access points but he shook his head. "Just plug 'em in," he said. "Here or in another room nearby -- that'll be cooler." A couple of the younger people at the table picked up two of the APs and headed for the hallway. "Put one on my desk," Lyman told them, "and the other at reception." Alan felt a sudden prickle at the back of his neck, though he didn't know why -- just a random premonition that they were on the brink of something very bad happening. This wasn't the kind of vision that Brad would experience, that far away look followed by a snap-to into the now, eyes filled with certitude about the dreadful future. More like a goose walking over his grave, a tickle of badness. The East Indian woman passed Kurt a VGA cable that snaked into the table's guts and down into the riser on the floor. She hit a button on a remote and an LCD projector mounted in the ceiling began to hum, projecting a rectangle of white light on one wall. Kurt wiggled it into the backside of his computer and spun down the thumbscrews, hit a button, and then his desktop was up on the wall, ten feet high. His wallpaper was a picture of a group of black-clad, kerchiefed protesters charging a police line of batons and gas-grenades. A closer look revealed that the protester running in the lead was probably Kurt. He tapped at his touchpad and a window came up, showing relative strength signals for two of the access points. A moment later, the third came online. "I've been working with this network visualizer app," Kurt said. "It tries to draw logical maps of the network topology, with false coloring denoting packet loss between hops -- that's a pretty good proxy for distance between two APs." "More like the fade," the graybeard said. "Fade is a function of distance," Kurt said. Alan heard the dismissal in his voice and knew they were getting into a dick-swinging match. "Fade is a function of geography and topology," the graybeard said quietly. Kurt waved his hand. "Whatever -- sure. Geography. Topology. Distance. It's a floor wax and a dessert topping." "I'm not being pedantic," the graybeard said. "You're not just being pedantic," Lyman said gently, watching the screen on which four animated jaggy boxes were jumbling and dancing as they reported on the throughput between the routers and the laptop. "Not just pedantic," the graybeard said. "If you have a *lot* of these boxes in known locations with known nominal throughput, you can use them as a kind of sensor array. When throughput drops between point foo and point bar, it will tell you something about the physical world between foo and bar." Kurt looked up from his screen with a thoughtful look. "Huh?"