As any fan of the Terminator franchise will tell you, once Cyberdyne Systems creates the world’s first Automated Defense Network (also known as Skynet) the countdown to nuclear Armageddon will begin in earnest. Which raises the question — if Skynet ever becomes a self-aware existential threat to our species… just how might we react?

Years before any sci-fi author thought up this nightmarish scenario the answer was revealed in a nuclear weapon test series labeled “Operation Fishbowl”. The first test in this series was codenamed Starfish Prime and was scheduled to better understand the impact of a 1.45 Megaton (mt) W-49 warhead in the upper atmosphere. The series began on July 9, 1962 when a single Thor missile launched from Johnston Island in the South Pacific and climbed 680 miles into the night sky. As the clock ticked past 11 o’clock in the evening the engineers and scientists noted that everything was progressing smoothly and they all sucked in a collective breath. Several seconds later the W-49 warhead blossomed into incandescent malevolence, and then everything started to go wrong. The culprit was an electromagnetic pulse (EMP) that was orders of magnitude larger than anticipated, stunning the scientists monitoring the test and exceeding the recording equipment’s ability to conduct accurate measurements. Despite the instruments failure, a clue to the power of this new and devastating aspect of nuclear warfare was indelibly etched on the infrastructure of the Hawaiian Island chain 900 miles east of the blast site. For in that instant on the far away island of Oahu, hundreds of streetlights flared and blinked into oblivion as their internal circuits fused.

To understand how a high-altitude nuclear explosion that presents no direct threat to human life can so thoroughly annihilate electrical systems requires a short overview of the dynamics of a nuclear generated EMP. As any fan of the Incredible Hulk will tell you, when a nuclear device detonates a fraction of the radioactive core is converted into a powerful form of ionizing radiation known as gamma rays. In nuclear detonations occurring at ground level this initial burst of gamma radiation is quickly absorbed by the thick belt of atmosphere blanketing the blast site. So the good news is a ground burst nuclear blast won’t cause an EMP (the down side is you will be vaporized and/or coated with radioactive debris).

When the same blast occurs in the upper reaches of the atmosphere there are far fewer air molecules for the gamma rays to interact with, allowing them to race outward in a rapidly expanding sphere. The enormous energy transmitted by the gamma ray literally rips the electrons from the parent molecules via the Compton process (imagine firing a cannon ball instead of a cue ball while breaking a rack in pool). The end result is a cascade of electrons following the gamma rays original trajectory, but now supercharged with millions of electron volts. This phase of a nuclear generated EMP is known as “E1”, and while it only lasts a billionth of a second it carries power density levels that exceed 50,000 volts per meter. There are two other EMP waveforms “E2” and “E3”, but for the purposes of our discussion we will focus on E1 due to it’s proven Skynet killing capabilities.

The process by which an EMP transfers energy into an electronic component is known as coupling. To visualize the coupling process it is useful to imagine the E1 pulse as a radio station that can only be picked up by the right type of antenna. In the case of E1 this can be any unshielded circuit, short power cable or integrated circuit capable of carrying an electrical charge. The latticework of delicate microcircuits in modern computers are designed to carry power measured in thousandths of a volt so when the E1 pulse pushes hundreds of volts into these channels they can literally melt and pool on the chips surface.

So there you have it — all we need to prevent being overthrown by computational overlords like Skynet is to detonate a high altitude nuclear weapon. And then sit down around our campfires looking forlornly at our dead screens and ponder how we will rebuild a world gone suddenly silent.