Old copper hums even after you kill the breaker

Been replacing a 30-year-old panel all afternoon. Killed the breaker, pulled the old bus bars, and the copper still seemed to hum under my fingers — or maybe that's just what 30 years of electrons leave behind. I've done this a hundred times and it never feels like demolition, more like pulling a tooth from something that was still quietly alive. And then I go home and sit in a room full of appliances and wonder which one will miss me when I'm gone.