By Steff Gaulter 

Many of us enjoyed a free visual spectacular on Wednesday last week. Lightning raged above Doha for several hours. Most people I know seem to like lightning, especially those of us who live in Qatar. I suppose part of this is because it’s relatively rare here, but personally I’m always impressed by the power of nature.                                                 

Most of us know that lightning is the discharge of electricity, just an electrical charge trying to neutralise itself, but it may surprise you to hear that even in this day and age, the processes that cause lightning aren’t fully understood. We know that the electrical charge builds up as particles within the cloud rub against each other, but the exact details are still unclear.

It is thought that the smaller particles tend to acquire positive charge, while the larger particles acquire negative charge. Being lighter, the smaller particles then rise to the top of the cloud, whereas the negative particles collect at the base.

The charges continue to build up until eventually electricity shoots through the air, creating a huge flash of lightning. A lightning bolt is usually about 5km (3 miles) long, but only about a centimetre (less than half an inch) wide. However, despite its narrow size, it can raise the temperature of the air by nearly 20,000 Celsius (50,000 F).

That is three times the temperature of the surface of the sun; no wonder getting struck by lightning can be so hazardous! The thunder that accompanies lightning is caused by the air expanding explosively, under the intense heat. This compresses the surrounding air, creating a ‘shock’ wave. The wave spreads out in all directions, and it is this which creates the noise that we hear as thunder.

Both lightning and thunder are generated at the same time, but usually they don’t always reach us at the same time, because light travels much faster than sound. We see lightning almost as soon as it happens, because light travels so fast. The exact speed of sound varies, depending on the temperature of the air and the amount of moisture in it, but it’s always much slower than the speed of light. On average it travels about a kilometre in three seconds (or a mile in five seconds).

Therefore in order to calculate how many kilometres away a storm is, we would just need to count the seconds between seeing the flash and hearing the thunder and divide by three (or five if you want to know the distance in miles). If you see the lightning and hear the thunder at the same time, then make sure you take cover! This means the storm is directly above you.

Most of the time the lightning simply rumbles away within the clouds. The negative charges at the bottom of the cloud find a path to the positive charges at the top of the cloud. This means the lightning simply illuminates the skies, and is beautiful without being harmful. However, lightning can also happen between the cloud and the ground, and this is obviously the dangerous kind!

If you saw a lightning strike in slow motion, you would see one stream of light reach down from the clouds, whilst much smaller, weaker beams of light reach up from the earth. When they meet, there is the huge flash of light, as current flows between the earth and the cloud. This is then followed by a series of strokes, sometimes as many as seven, until the electricity has completely discharged.

Obviously being hit by lightning is incredibly dangerous and can be fatal. However, it may surprise you to hear that a direct lightning strike isn’t quite as terminal as you might think. Only about 10%  of people who are struck by lightning are actually killed, and strangely, if you are hit when it is absolutely teeming with rain, you may well fare better than if it were dry. That’s because water is a good conductor of electricity, so the electricity will go through the water around your skin, rather than through your body.  

However, it’s not just a direct hit from lightning that can be dangerous. It’s important to remember that when the lightning strikes the ground, the electricity doesn’t simply stop. Many people who are injured by lightning are struck as the current moves in and along the ground. This is why standing next to a tall tree is not such a good idea during a thunderstorm!

There’s also the risk of being struck by lightning before the thunderstorm has even arrived. Most lightning originates from the bottom of the cloud, where the charge is negative, however, occasionally lightning can stem from the top of the thunderstorm. This is the area that carries a large positive charge, and ‘positive lightning’ usually occurs as a thunderstorm is petering out.

Although the storm is weakening, positive lightning is the most dangerous type of lightning, because people often don’t realise they’re at risk. Positive lightning has been known to strike as far as 16 kilometres (ten miles) from the storm.

Cases of injury from lightning in Qatar are, thankfully, very rare. However, knowing more about this natural wonder can help us all to appreciate its power and beauty.

 


 

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