Using a fast-pulsing laser, physicists have recorded the first moments of electrical resistance, the friction that generates heat as electricity travels through circuits.
Physicists knew electrical resistance didn’t kick in the moment a voltage was applied. Electrons experience some freedom before slowing to a crawl and scattering. What wasn’t certain was how quickly they make that transition (illustrated in the animation above, with electrons in blue, “electron holes” left by departing electrons in red, and voltage signified by the green arrow).