A building in Pune has been struck by lightning for the second time in one monsoon, in what residents describe as a “direct insult” to one of the country’s most trusted sayings.
“Lightning never strikes the same place twice,” said Mr Vinod Bhalerao, 58, standing on the terrace of the building’s twenty-third floor in a thunderstorm, holding an umbrella. “I have organised my whole life around this. After the first strike, I came up here every storm. It was the safest place in the city. Now what am I supposed to do?” He was gently led inside by his neighbours, who confirmed that the umbrella’s metal tip had been, as one of them put it, “really not helping”.
Scientists, approached for comment, said the saying was “wrong in the most dangerous possible direction”. Lightning does not keep a record of where it has been. What it has is a strong preference, the same every time, for whatever is tallest and pointiest underneath it.
A thunderstorm, they explained, is a giant electrical machine. Inside the cloud, ice crystals and soft hail collide in violent updrafts, and the collisions strip charge from one to the other, until the bottom of the cloud is heavily negatively charged. That charge pulls positive charge up into the ground beneath it, which collects most strongly on anything that sticks up: trees, towers, and the corners and railings of tall buildings. Points are especially good at this. The electric field around a sharp tip is much more intense than around a flat surface, which is why sparks always jump from the corner of something, never the middle.
When the cloud finally discharges, a faint, branching channel of charge feels its way down from it in jumps. As it gets close, the intense field at the tips of tall objects below launches sparks upwards to meet it. Whichever upward spark connects first completes the path, and the main stroke, the blinding flash, races along it. A twenty-three-storey building with a steel railing sends up its spark long before the ground around it does. It will do so in every storm, for as long as it stands.
“Tall buildings get hit all the time,” said one scientist. “The Empire State Building in New York is struck around twenty or twenty-five times a year. That is not bad luck. That is geometry.”
This is also why the building has a lightning rod, a pointed metal conductor on the roof, connected by a thick cable to a metal plate buried in the ground. The rod doesn’t summon lightning from anywhere it wasn’t going to strike. It gives the current, tens of thousands of amperes for a tiny fraction of a second, a path with very low resistance straight into the earth, instead of through bricks, wires and residents. Both strikes this monsoon, the society secretary confirmed, went down the rod, and the only damage was to Mr Bhalerao’s confidence.
Mr Bhalerao says he has accepted the science and will no longer stand on the roof. He has instead identified a new safe spot, under the tallest tree in the society garden, “since the tree has never been hit”. Neighbours are gently leading him inside again.
Try it yourselfMake a tiny lightning bolt
- In a dark room, shuffle your feet across a carpet, or rub a woollen jumper hard against yourself.
- Slowly bring the tip of the key towards a metal door handle or tap.
- Watch closely for a tiny spark, and listen for its crack.
- Try again with your fingertip instead of the pointed key. Which gives you the less painful spark?
What's going on?
You have charged yourself up, like a cloud. As the key nears the metal, the electric field at its point grows strong enough to tear electrons from the air and make it conduct, and charge jumps across as a spark. Points concentrate the field, which is why the key sparks more easily, and why lightning so often finds the tallest, sharpest thing around. The tiny crack is a very small thunder.
Safety Only use a key or spoon and a metal tap or handle. Never try this with sockets, appliances or anything plugged in.