Electromagnetic pulses, or EMPs, are energy bursts that can disrupt electronic equipment, but how do they do it? The answer is in the design of modern electronics. Admiral Hyman Rickover famously carried an 11 inch piece of wire with him that he would show to people to represent the need to make computers smaller. That’s the distance that an electron can travel in one nanosecond. When measured against the intricate circuitry of a microprocessor, 11 inches isn’t that far. In order to make more efficient processors, the circuits have to shrink so that electrons can travel a little farther in that nanosecond. Since computer clocks work at those time frames, that physically limits the amount of information that can travel through the processor during a given clock cycle.
As processor manufacturers have made their products smaller to mitigate this physical limitation, the tiny wires inside them have become closer and closer together. Today, processors are built with miniscule distances between wires to maximize the density of circuits that can be fit onto a processor die. 25 nanometers isn’t an unusual gap between wires in modern processors.
An EMP floods a processor with loose electrons that bridge those small gaps and cause short circuits. It’s the same principle that causes a short circuit in a lamp cord, just at a smaller scale. Since processors aren’t designed to ground those short circuits like your home fuse box, the wires inside become fused and the processor becomes useless. Even the simplest devices in our society use microcircuitry to improve their efficiency, making almost every device we carry vulnerable to an EMP.