An EMP, or electromagnetic pulse, is a burst of electromagnetic energy that can disrupt or destroy electronic devices and electrical systems. EMPs can come from natural sources like lightning and solar storms, or from man-made sources like nuclear detonations and specialized weapons. The concept has been a growing concern for governments and infrastructure planners because a large-scale EMP event could knock out power grids, communications, and electronics across a wide area.
How an EMP Works
Every electronic device operates using small electrical currents flowing through circuits. An EMP sends a sudden wave of energy through the air that, when it hits these circuits, induces a voltage spike far beyond what the device was designed to handle. Think of it like a massive power surge, except instead of coming through a wall outlet, it arrives through the air and hits everything at once.
The pulse couples into anything that acts as an antenna, especially long conductors like power lines, cables, and metal structures. The longer the conductor, the more energy it absorbs. This is why large-scale infrastructure like electrical grids is particularly vulnerable, while a short wire inside a small device picks up comparatively less energy.
Natural Sources of EMPs
Lightning is the most common natural EMP. Each strike generates a localized pulse near the point of contact, which is why lightning can fry nearby electronics and trip circuit breakers. The effect is intense but limited to a small area.
Solar storms are the far bigger natural threat. The sun periodically releases massive bursts of charged particles called coronal mass ejections. When these reach Earth, they interact with the planet’s magnetic field and can induce electrical currents in long conductors on the ground, particularly power lines and pipelines. Most solar flares don’t last much longer than an hour, but the ground-level effects of a major geomagnetic storm can persist for days.
The most famous example is the 1859 Carrington Event, which was powerful enough to cause telegraph systems to spark and catch fire. Recovery took several days, though the damage was limited because widespread electrical infrastructure didn’t yet exist. A Carrington-scale event today would be a very different story.
Man-Made EMPs
During Cold War nuclear testing, researchers discovered that nuclear detonations produce extremely powerful EMPs. The most dramatic demonstration came in 1962, when the U.S. military detonated a nuclear warhead called Starfish Prime high above the Pacific Ocean. Nearly 900 miles away in Hawaii, streetlights went dark and inter-island communications from Kauai were severed. The EMP signal propagated down to the ground and coupled into power lines, triggering blackouts across the islands.
A nuclear EMP works differently from a solar storm. A high-altitude nuclear detonation produces three distinct phases of pulse: an extremely fast initial burst (arriving in nanoseconds) that damages small electronics, a middle phase similar to lightning, and a slower pulse that behaves like a geomagnetic storm and threatens long-line infrastructure. Solar storms only produce the slow variety, which is why they primarily threaten power grids rather than individual devices.
Beyond nuclear weapons, militaries have developed non-nuclear EMP devices. The U.S. Navy, for example, researches high-power microwave (HPM) weapons that create focused beams of electromagnetic energy across radio and microwave frequencies. These are designed to disrupt or damage electronics in targeted systems, either destroying them outright or causing disruptions the system can’t recover from quickly enough to complete its mission. Non-nuclear devices are far more limited in range than a nuclear EMP, but they can be aimed at specific targets.
What an EMP Could Damage
The electrical grid is the most critical vulnerability. High-voltage transformers, the massive units that step power up and down across the grid, can suffer insulation breakdown when hit with the fast voltage spikes an EMP produces. These transients arrive in as little as 2.5 to 20 nanoseconds and can cause failures in oil-insulated transformers and their bushings. Replacing large power transformers is not quick. They’re custom-built, weigh hundreds of tons, and can take over a year to manufacture. A sufficiently powerful EMP could knock out major electrical grids for weeks or months.
Communications systems, internet infrastructure, and anything connected to long cables or antennas would also be at risk. Banking systems, water treatment plants, hospitals, and other critical services that depend on both electricity and networked electronics could cascade into failure even if their own equipment survived the initial pulse.
Cars are a common concern, but the reality is less dramatic than fiction suggests. The U.S. EMP Commission tested 50 vehicles manufactured between 1987 and 2002. Only three shut down while driving, and of those, two restarted afterward without any issues. Just one vehicle refused to restart entirely. Modern cars have more electronics and might respond differently, but the idea that every vehicle on the road would instantly die is not supported by the available testing.
How Governments Are Preparing
In 2019, the United States issued Executive Order 13865, formally establishing it as national policy to prepare for EMP effects. The order directed federal agencies to provide warning of impending EMP events, protect critical infrastructure, and encourage private-sector investment in resilience. It specifically tasked the Department of Homeland Security with assessing which national critical functions and infrastructure face the greatest risk.
The practical priorities include risk-informed planning across all critical infrastructure sectors, research and development to address vulnerabilities in power systems and communications, and deterrence strategies against adversarial use of EMP weapons. The order also called for incentives to encourage private companies to adopt best practices and develop technology that can withstand EMP effects.
On the personal level, the same principles that protect against power surges offer some EMP protection. Faraday cages (metal enclosures that block electromagnetic fields) can shield small electronics. Unplugging devices removes their connection to long conductors that would channel the pulse indoors. Surge protectors help with smaller pulses, though a full-scale nuclear EMP would likely overwhelm standard consumer models. For most people, the practical risk from EMPs is less about protecting individual gadgets and more about being prepared for an extended power outage, with stored water, food, cash, and battery-powered communication like a hand-crank radio.