Reportage
First-hand accounts
Metaphorical
Last summer in the Bavarian Alps, I watched a thunderstorm from a weather station at 1,800 meters. Three seconds passed between the first flash and the clap of thunder – the lightning struck about a kilometer away. In those three seconds, so many physical processes took place that they could fill a textbook. But let's break it down, step by step.
How an Electric Storm Begins
«Lightning isn't just a discharge. It's the result of a complex electrical machine operating within the cloud», explains Dr. Klaus Steinmüller from the Max Planck Institute for Atmospheric Physics in Munich, whom I met the day after that memorable storm.
It all starts with the movement of air masses inside a thunderstorm cloud. Updrafts lift small water droplets and ice crystals upward to where temperatures can drop to −40 °C. Downdrafts pull larger particles down.
When they collide, a transfer of electrons occurs – a physical process called triboelectrification. Imagine rubbing a balloon on a wool sweater, but on a scale where the «balloon» is the size of a football field, and the «sweater» is billions of ice crystals.
The result is predictable: the top of the cloud accumulates a positive charge, while the bottom becomes negatively charged. The potential difference can reach 100 million volts. For comparison, a household outlet is 230 volts.
Invisible Steps to the Ground
«What we see as lightning is actually the finale of a long process», says Steinmüller, showing a high-speed video of a discharge. The recording reveals what the human eye can't see: lightning moves in steps.
First, an invisible channel of ionized air – a stepped leader – begins to advance from the cloud toward the ground. It moves in a zigzag pattern, as if searching for the path of least electrical resistance. Its speed is about 50,000 meters per second. That sounds fast, but by electrical standards, it's a snail's pace.
The leader moves in 50–100 meter segments, then pauses for microseconds before jumping forward again. At each stop, it «assesses» the surroundings: where the air is more humid, where there is more dust, where the density of molecules is lower. This is why lightning has a jagged shape – it bypasses obstacles at the molecular level.
When the leader gets within 100–200 meters of the ground, something interesting happens. From tall objects like trees, buildings, and lightning rods, a streamer rises to meet it. This is the upward leader, which moves much more slowly, at a speed of about 10,000 meters per second.
The Moment of Contact
«When the leaders meet, the real show begins», the physicist comments. At the point of contact, a conductive channel, 2–5 centimeters in diameter, forms instantly. An enormous return stroke rushes through this channel from the ground back to the cloud at the speed of light – 300 million meters per second.
It is this return stroke that we see as lightning. It carries a current of 20,000 to 200,000 amperes. For context: a standard light bulb uses less than one amp, and a welding machine uses about 200 amps.
The channel's temperature instantly rises to 30,000 °C – five times hotter than the surface of the Sun. The air expands explosively, creating a shockwave that we hear as thunder.
The entire process – from the first movement of the leader to the completion of the return stroke – takes about 0.2 seconds. But a person only perceives the last 0.0002 seconds, when the main channel is illuminated.
Why Lightning Strikes a Specific Spot
As children, we were told lightning strikes the highest point. That's true, but it's not the whole story. «Height is only one factor», Steinmüller explains. «The electrical field also considers the object's shape, material, and the humidity of the surrounding air.»
Pointed objects create a stronger electric field at their tips – a physical phenomenon known as the point discharge effect. This is why lightning more often hits spires, antennas, or solitary trees. But it can also strike a flat surface if the conditions are right.
The material's conductivity is also important. Metal structures attract a discharge more strongly than wooden ones. Moist soil conducts electricity better than dry soil. Therefore, the probability of a strike in a specific location increases during rain.
Interesting fact: lightning can strike the same spot multiple times in a row. The famous Empire State Building in New York is hit about 25 times a year, sometimes several times during a single thunderstorm.
What Happens to the Current in the Ground
After a strike, the electrical current doesn't just disappear – it spreads radially across the ground from the point of impact. «The current looks for a way back to the cloud through any conductive objects», the physicist explains. «Metal pipes, tree roots, underground cables.»
Within a 30-meter radius of the strike point, the voltage can reach several thousand volts. This explains why it's dangerous to be near a place that has been struck, even if the discharge didn't touch you.
Step voltage is especially dangerous – the potential difference between two points on the ground's surface that are one step apart. If you stand with your feet at different distances from the strike point, a current will flow through your body.
This is why rescuers recommend crouching with your feet together during a thunderstorm. This minimizes your contact area with the ground and the chance of being affected by step voltage.
Different Types of Lightning
What we usually call lightning, physicists classify into several types. The most common are negative lightning strikes, which transfer a negative charge from the cloud to the ground. They account for about 90% of all discharges.
Positive lightning is rarer but more powerful. The current can reach 300,000 amps, and the duration of the discharge can be up to half a second. They strike from the upper, positively charged part of the cloud and can travel distances of up to 25 kilometers.
«A positive lightning strike can come from what looks like a clear sky», Steinmüller warns. «The thunderstorm cloud may be far away, but the discharge strikes dozens of kilometers from it.»
There are also intracloud lightning strikes – discharges between oppositely charged regions of the same cloud. They are not visible from the ground, but they make up to 75% of all electrical discharges during a thunderstorm. And intercloud lightning, which connects neighboring storm cells.
Rare Forms of Discharges
Besides common lightning, more exotic electrical phenomena occur in the atmosphere. Sprites are red flashes above storm clouds at altitudes of 50–90 kilometers. They were only discovered in 1989 because they last for a few milliseconds and are only visible from space or very long distances.
Elves are circular flashes at an altitude of about 100 kilometers that spread at the speed of light and reach a diameter of 400 kilometers. Blue jets shoot upward from the tops of storm clouds to altitudes of 40–50 kilometers at a speed of about 100 kilometers per second.
«We're discovering new types of discharges every few years», says Steinmüller. «The atmosphere is a more complex electrical system than we thought just 30 years ago.»
The Energy of Lightning: The Myth of Practical Use
You often hear the idea: what if we could harvest the energy from lightning? The numbers seem impressive: a single discharge carries from 1 to 5 billion joules of energy. But there's a catch.
First, most of the energy is dissipated as heat, light, and sound. Only about 250 kilowatt-hours reach the ground – about as much as an average German home consumes in a week.
Second, lightning is unpredictable. You can't know in advance when or where it will strike. Third, the peak power of a discharge is enormous, but it only lasts for microseconds. Existing technologies don't allow for the effective storage of such energy.
«Trying to use lightning energy is like trying to fill a glass from a fire hydrant», the physicist explains figuratively. «Theoretically possible, but practically pointless.»
Lightning Protection: How a Lightning Rod Works
Benjamin Franklin invented the lightning rod in 1752, and its principle hasn't changed. It's a metal rod placed at the highest point of a building and connected to the ground by a thick conductor.
«A lightning rod doesn't 'attract' lightning», Steinmüller clarifies. «It provides a preferential path for the discharge.» When a stepped leader approaches the building, an upward streamer rises from the pointed tip of the lightning rod. The lightning strikes the rod, and the current safely travels into the ground.
The protection zone of a lightning rod is cone-shaped with an angle of about 45°. A 20-meter-tall building needs a lightning rod at least 2 meters above the highest point of the roof.
Modern lightning protection systems include not only rods but also a grid of metal conductors that cover the entire building. This system is called a Faraday cage and provides protection even in a direct lightning strike.
Lightning and Humans: Survival Statistics
Contrary to popular belief, a lightning strike is not always fatal. According to the U.S. National Oceanic and Atmospheric Administration, the survival rate is about 90%.
«The human body is a poor conductor of electricity», says Dr. Steinmüller. «The current more often passes over the surface of the body than through internal organs.» This phenomenon is called external flashover.
The most common consequences of a lightning strike are skin burns, temporary paralysis, and heart rhythm disturbances. Serious internal damage occurs when the current passes through the body – for example, from hand to foot.
Interesting fact: some people have survived lightning strikes multiple times. Roy Sullivan, a park ranger in Shenandoah National Park, was struck by lightning seven times between 1942 and 1977 and survived all seven.
How to Predict Lightning
Modern meteorologists can predict a thunderstorm 6–12 hours in advance, but the exact location and time of a lightning strike can only be predicted seconds before. This is done using detectors of electromagnetic pulses.
«Every lightning strike emits radio waves across a wide range of frequencies», Steinmüller explains. «A network of detectors registers these pulses and calculates the location of the discharge using triangulation.»
In Europe, the EUCLID network operates, which includes over 160 detectors. The accuracy of location determination is about 150 meters, and processing time is less than 10 seconds. The data is used to warn aviation, power companies, and organizers of public events.
Personal lightning detectors, sold to hikers and athletes, work on the same principle. They detect electromagnetic pulses up to 65 kilometers away and warn of an approaching storm 8–20 minutes in advance.
Myths and Misconceptions
A lot of myths have formed around lightning. «Lightning can't strike the same place twice» is false. On the contrary, a place that has been struck once has a higher chance of being hit again.
«Rubber shoes protect you from lightning» is also a myth. At a voltage of millions of volts, a few millimeters of rubber play no role.
«It's safe in a car because of the rubber tires» is inaccurate. The car is protected not by the rubber but by the metal frame, which acts as a Faraday cage. The current passes through the metal and goes to the ground via the tires.
«Lightning prefers metal objects» is partially true. Metal doesn't attract lightning, but it provides a better path for the current. Therefore, tall metal objects are struck more often.
Lightning on Other Planets
Earth isn't the only place in the universe where electrical discharges occur. The Cassini spacecraft detected lightning on Saturn. Some of them lasted for over an hour and were a thousand times more powerful than Earth's.
There is more lightning on Venus than on Earth, despite its dense atmosphere of carbon dioxide. On Jupiter, thunderstorms can be the size of Earth and last for months.
«Lightning is a universal phenomenon wherever there is an atmosphere and gas movement», the physicist comments. «Studying lightning on other planets helps us understand the physics of electrical discharges in extreme conditions.»
As I was leaving the laboratory at the Max Planck Institute, storm clouds were gathering outside the window again. Now I looked at them with new eyes – understanding what a complex physical machine was at work up there, getting ready to put on one of nature's most impressive shows.
Every flash in the sky is the result of billions of particle collisions, precise electrical field calculations, and the instantaneous heating of the air to the temperature of a star. And it all happens in a time frame that a human doesn't even have time to comprehend.
