There is an old saying that lightning doesn’t strike the same place twice. People use it to comfort and reassure* someone who has had bad luck.
Unfortunately, the saying isn’t true.
Lightning does often strike the same place twice and a new international study shows how, solving a big mystery.
Scientists used a specially made telescope to look inside thunderclouds and watch what happens when lightning strikes.
The research team identified what they call ‘needles’. These become a channel between the clouds and the strike place for the electricity to move through. These ‘needles’ store a negative charge along the main lightning channel. The negative charge attracts more lightning and so causes repeated strikes.
The research team led by the University of Groningen in the Netherlands and involving a scientist from The Australian National University (ANU) used a radio telescope to crack the long-running lightning mystery.
WHAT IS LIGHTNING?
Clouds are made up of water and ice. Air currents push up and gravity pushes down and the water and ice are compressed, or squashed together.
The particles in the clouds collect an electrical charge from all that pushing about, just like the electrostatic charge you create when you rub a balloon on your hair.
Lightning strikes when so much electricity builds up in a cloud it is strong enough to break out of the clouds and into the air. The lightning bolt travels through the channel and hits the ground within a fraction* of a second after passing through a channel.
WHAT IS THUNDER?
The sound of the air collapsing back into the channel the lightning has just passed through makes the sound of thunder. We see lightning before we hear thunder because light moves much faster than sound.
If you hear thunder at the same time or very soon after you see lightning, the storm is close by.
According to the Bureau of Meteorology (BOM), lightning causes up to 10 deaths every year in Australia.
ANU Emeritus* Professor Harvey Butcher said the research team studied the development of lightning flashes, creating extremely high-definition 3D images of how the lightning forms and strikes.
“The reason why a lightning channel is reused had been a mystery until now,” said Professor Butcher, a former Director of the ANU Research School of Astronomy* and Astrophysics.
“This new research shows the negative charges inside a thundercloud are not drained all in one flash but are, in part, stored alongside breaks in the main lightning channel.
“This happens in structures called needles that have never been described before. Through these needles, a negative charge may cause a repeated discharge* to the ground.”
Professor Butcher led the development of the telescope used by the team. The radio telescope, LOFAR (LOw Frequency ARray), is made of thousands of simple antennas spread across Northern Europe.
These antennas are connected with a central computer, which means they can operate together to form a radio camera able to focus on both the distant Universe and on phenomena* — such as lightning — in the Earth’s atmosphere.
The findings are published in the science journal Nature.
Lead author Dr Brian Hare from the University of Groningen said the information collected by LOFAR allowed the team to detect lightning activity within clouds and the surrounding environment at a scale where, for the first time, scientists can properly understand what is happening.
“From these observations we see that a part of the cloud is recharged, and we can understand why a lightning discharge to the ground may repeat itself a few times,” he said.
“The use of radio waves allows us to look inside the thundercloud, where most of the lightning resides*.”
This is an edited version of a story by ANU, reproduced here with permission.
- STAYING SAFE AROUND LIGHTNING
Stay indoors and move away from windows, doors and skylights.
- If you are outdoors, move indoors or into a solid-top (not convertible) car that is not parked under trees.
- If far from shelter, crouch with feet together, preferably in a low spot such as a ditch. Don’t lie down flat but avoid being the highest object.
- If you hear buzzing from nearby rocks or fences or your hair stands on end, move away.
- Don’t fly kites or model aeroplanes with control wires or use umbrellas, fishing rods or golf clubs.
- Don’t ride a bike or a horse.
- If swimming, leave the water immediately.
Source: Bureau of Meteorology
- reassure: say or do something to remove doubts
- fraction: small part of
- emeritus: retired professor
- astronomy: science of objects in space, such as planets and stars
- astrophysics: physics and chemistry branch of astronomy
- discharge: allow something to flow out from where it has been
- phenomena: things we observe, particularly things we can’t easily explain
- resides: where something lives or is
- What is thunder? Why do you hear it after lightning?
- The radio telescope used is made up of thousands of what?
- Where does Dr Hare say most of the lightning is during a thunderstorm?
- Should you stay indoors or go out if there is a thunderstorm?
- Explain two of the safety tips.
LISTEN TO THIS STORY
1. Thunder and Lightning
Sketch a landscape including thunder clouds and lightning bolts and surround your picture with dot points explaining how thunder and lightning are generated. Try and keep your language simple so other children can understand and make your landscape picture interesting and colourful to grab people’s attention.
Time: allow 20 minutes to complete this activity
Curriculum Links: English, Visual Arts, Science
Under the heading “Lighting CAN Strike Twice”, write a list using dot points of why lightning is likely to strike more than once in the same location.
Time: allow 10 minutes to complete this activity
Curriculum Links: English, Science
Create a visual poster of all the ways you can stay safe around storms and lightning.
Use your VCOP to uplevel some of the language used to caption your visual picture. You may want to add more information to your caption to be more effective.
HAVE YOUR SAY: Is anyone you know frightened of thunderstorms?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.