What is Lightning?
Lightning is not a rare event. The US Lightning Detection Network registers over 20 million earth-bound lightning flashes per year. Worldwide, approximately 860,000 lightning flashes occur each day and during the time it takes for you to blink, several thousand lightning bolts strike the ground or water somewhere. Lightning is a frequent and random weather phenomenon.
The weather services can’t predict where lightning will strike. But they can warn whenever thunderstorms are likely to develop. Then it is up to you to take the appropriate precautions.
The Oxford Dictionary defines lightning as: ‘… the occurrence of a natural electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud, accompanied by a bright flash and typically also thunder.’
How does lightning form? Scientists aren’t very sure, but support one popular theory. Strong turbulence within a thunderstorm cloud forces raindrops and ice crystals to collide. The drops and crystals stick together and grow bigger. They can’t always sustain their size in the turbulent air and often split again into smaller fragments of unequal size. Experiments show different charges in the fragments. The smaller pieces are negatively charged whereas the larger pieces are positively charged. Updrafts and downdrafts take the fragments to different parts of the cloud, thus creating an imbalance of electrical charge within the cloud and between the cloud and the ground. Sparks will fly, literally, when the opposing forces are able to overcome the insulating property of the air. And what sparks they are. A lightning flash is the result of around 200 million volts’ potential difference, and discharges in a current of several thousands amperes.
Most lightning occurs within the clouds. Only about 20% strike the surface. Because air is a good insulator, the lightning tends to take the shortest route towards a high object on the surface or a path with least resistance. If you are on a boat with your new graphite fishing rod in your hand, you are likely to be the highest point and an ideal target for a strike – a lightning strike, that is.
With lightning comes thunder. A lightining bolt heats the air in its path to over 40,000°C, causing it to expand rapidly and send out a strong shock wave. Your ear receives the change in air pressure and registers it as a loud noise.
Lightning injuries, damage and death
With population growth, lightning damage to property increases. The US National Weather Service (NWS) estimates an annual cost to US society of A$70 million. The National Lightning Safety Institute, however, takes into account the indirect costs of bushfires, power blackouts, aircraft mishaps, and estimates a damage bill of around A$10 billion per year.
Do you play lotto? The odds that your six numbers are drawn from the 49 tumbling balls is around one in 14 million. You have a much better chance to be hit by lightning – less than one in half a million.
The US weather service reports approximately 100 deaths and 500 injuries per year from lightning strikes but other agencies believe that, due to under-reporting, the number of fatalities should be around 450. Australia has up to 10 deaths and well over 100 injuries per year. Conservative estimates put the worldwide toll at 1,000 deaths and 5,000 injuries annually. This makes lightning deadlier than tornadoes.
Nevertheless, the numbers show that you won’t necessarily die when you are hit by lightning. If you use the US figures, the mortality rate is 20%, whereas the Australian rate is 10% of all lightning hits. But some studies suggest that, due to frequent underreporting of lightning injuries, the rate should be below five per cent. In other words, the survival rate is very high.
When you imagine a strike, you probably picture a lightning bolt enter a person’s head and leave via the feet – a direct strike. Of course, this is the most deadly form of lightning strikes. Eighty per cent of victims don’t survive. Fortunately, direct strikes are rare.
More common are indirect hits. Lightning often seeks a prominent object on the ground such as a tower or tree. The current enters a person in contact with the object – contact potential – or arcs a short distance to a person nearby – side flash. Sometimes the current travels through the soil and enters the body parts in contact with the ground, step voltage. In all cases, the object or the ground takes the brunt of the energy and the person has a good chance of survival.
Metal is a good conductor of electricity. It is, therefore, no surprise that a person in contact with or in proximity of electric cables, water pipes, household appliances or the telephone can become a victim of a lightning strike – surge propagation. Death is rare, but injuries are relatively common, in particular while using the telephone.
Lightning doesn’t leave your remains in a pile of smoking ashes. Cardiac arrest is the main cause of death. Quite often, though, the heart automatically begins to beat again, but lack of oxygen, caused by a paralyzed breathing mechanism, may stop the heart for a second time. A direct hit often causes horrific burns or scalding from evaporating moisture on the skin and in the lungs. In most cases, however, the human body acts like the shell of a car. The current flashes along the outside into the ground. Like the metal exterior of a car, the skin of a human protects its contents. In this case, survivors sometimes have no physical problems and clinical tests show normal results. They may see their physician with other serious after-effects, though.
Lightning injuries are different from household or industrial electric shocks and often misunderstood by the medical profession. Specialists in keraunomedicine study the effects of lightning strikes.
Apart from being deadly, a lightning strike can cause a number of injuries and disorders. Some of the known effects are:
> External and internal burns and scalding
> Chronic pain
> Severe headache
> Severe ear damage, hearing loss, tinnitus
> Stiffness in joints, muscle spasm, numbness
> Sleep disturbance
> Memory loss, attention deficit
> Depression, inability to cope, irritability
> Dizziness, coordination problems, confusion
> General weakness, chronic fatigue
> Reduced libido
Lightning is random and, therefore, very unpredictable. You as an individual must take responsibility for yourself and persons in your care. All tips and safety measures are only designed to minimize the risk, not to provide absolute protection. Take the following precautions:
- Listen to warnings. While no forecaster can predict the place of a ligthning impact, he or she can issue a warning that thunderstorms will occur in your region. This is the time to plan your activities accordingly.
- Recognize the danger. Large clouds extending high into the atmosphere with a dark and flat bottom and a feathery anvil-shaped top are most likely thunderstorm clouds (cumulonimbus). Soon you either see the first flashes or hear some distant rumbling. Estimate the distance by counting the time between a flash and the arrival of the thunder. For every kilometer the sound takes about three seconds to travel. This doesn’t work if you have a serious of flashes and you can’t associate a single flash with the arriving thunder. When the thunderstorm has passed, suspend all activity for another 30 minutes. Lightning may still be present in a dying thunderstorm. Statistics prove that the most dangerous times for lightning injuries are just before and at the apparent end of storms.
- Seek shelter. Electricity likes to flash around the outside of an object. With exceptions, of course, a car or a house provides good protection. Avoid shelter under trees or any other tall and free-standing structure.
- Outdoors. If you are the coordinator of an outdoor event, plan the evacuation and safety measures well in advance. Suspend activities when you see lightning or hear thunder. Whether you are a group or a single person, avoid high ground, open spaces, water, and metal objects. Definitely don’t be the highest point in the surrounding space.
- Indoors. Lightning can enter your house via electric wiring, phone lines or water pipes. Do not use electric appliances and avoid phone calls. Don’t take a bath or a shower.