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    Saturday, 29 October 2016

    Lightining, the terror of summer; understanding and dealing with it

    SUMMER is with us now and everyone is eagerly expecting some rainfall as evidenced by the upsurge in the number of people clearing the land on the countryside and the sudden materialisation of stockpiles of seed in the shops resulting in a number of people emerging from the said shops carrying seed packs towards home.
    Rainfall is the key to a wide range of business enterprises, the success of the Agrarian Reform rests on adequate rainfall let alone skilful management
    Rainfall, however, is accompanied by one, if not the greatest and least understood terrors of mankind; LIGHTNING. In this expose, I shall endeavour to explain from a Geographic-Scientific background, the physics of lightning, magnitude of damage to man and animals. I shall explain the speed of lightning, its benefits to man and the environment and attempt to suggest practical precautions.
    Beliefs about lightning
    Lightning as a natural phenomenon has had numerous explanations by different cultures, races and religions. The nature of electricity has always been a mystery and remains so regardless of the vast strides made in the knowledge of the atom and the remarkable strides in electronics.
    Plutarch tells us that Anaxagorus thought lightning to be little flames escaping from the stars. Seneca who seemed more observant thought it was caused by the collision of clouds. In Greek mythology they regarded lightning as the flaming spear of their great god Zeus and in the Netherlands it was the flashing hammer of Thor whose rambling chariot caused the thunder. Even until recently, electricity was thought to be a kind of universal fluid, something akin to the all-pervading other, the mythical substance of space.
    The Bantu people have a particular fear of lightning. In the seventies it was anathema or taboo to wear a red item of clothing when there was a lightning storm and thunder. In the classroom groupmates would abandon a group where a mate wearing a red colour would attract lightning and when the person is struck then the shrapnel would rebounce on them killing them too.
    The Bantu still believe that anyone struck by lightning is thought to have incurred the wrath of the Great Spirit and is regarded as unclean. If the victim survives, he must go through an elaborate cleansing ceremony, if he dies, he is buried immediately. It is believed that livestock killed by lightning is not used for food.
    A curious belief still prevalent among the traditionalists is, that a kind of thunderbird is responsible for the phenomenon of lightning and, when trees are struck, areas surrounding the hit spot are searched meticulously for the eggs of that bird which, they believe, with lightning phobia, might later hatch out and cause further mischief.
    Witchcraft practitioners are usually credited for directing thunderbolts to their enemies. In numerous cases, people have been accused of possessing an armoury of lightning.
    In January 1991, I was deployed by choice to Siabuwa Secondary School in Binga. I arrived on a rainy Monday of the schools' opening week and there was news of a man who had been hit and killed by lightning on that very day.
    In the second week of my stay at Siabuwa Secondary School someone was struck by lightning on a Tuesday.
    In the third week someone was struck dead on a Wednesday. In week four, the victim was a woman who was struck a hundred metres from a form three classroom where I was conducting an English language lesson. The rains arrived about fifty minutes after the death of the woman.
    During week five, a man was hit on a Friday and luckily he survived the ordeal. World spread that the owner of the lightning was boasting that the trade testing of his weapon imported from Zambia was a successful.
    The physics of lightning
    Lightning in nature is just electricity caused by the positive and negative charges of electricity formed by the friction occurring among air particles between the clouds and between the clouds and the earth.
    Normally clouds called "The Weather Factory" in the USA, or commonly called the Cumulonimbus clouds are the fertile grounds for lightning to occur. These clouds form where atmospheric conditions are such as to cause rapid heating and violent air currents over either large or small areas.
    These currents cause clouds with bases at 600m to 2000m from the ground. The tops of these clouds may reach to as high as 20km. Friction between air, ice crystals and air molecules produce static electricity with negative charges collecting at the bottom or base of the cloud and positive charges collecting at the summits of the clouds.
    When it is raining the raindrops contain some potential energy in them which, when they fall produces positive charges of electricity at the top of the weather factory and a negative charge at the base of the cloud. The ground subsequently becomes positively charged.
    When the above situation occurs, then we automatically have a fully charged power station. Lightning is caused by a small local discharge that occurs when the positive charge touches the negative charge thereby causing a short circuit. When that occurs elections are released which then travel in a series of steps each about 50metres in length. Each step takes less than a microsecond with the time between steps of about five microseconds, so that the total microsecond's journey to earth takes about 20milliseconds. When the stepped ladder nears the ground, a corresponding positive charge concentration occurs in the ground especially at elevated points. The stream of electrons in the ladder rapidly contacts the elevated point and the negative charges are violently squeezed out of the ladder, causing a large current flow near the earth.
    This loss of negative charges above the ground and the phenomenon is rapidly propagated up the ladder. Where the current is heavy, the air becomes luminous, it glows, and and so the flash travels from the ground to the cloud at a speed which is about one tenth of the speed of light. Light travels at approximately 330m per second. This process may be repeated several times at the same spot. Lightning hits from the ground to the air or sky.
    The flash may produce temperatures of up to 15000 degrees Celsius to 35000 degrees Celsius which is several times the temperatures of the surface of the sun. This sudden heating of the air causes the air to expand rapidly and create a shock wave which we hear as thunder. When the strike hits a tree, the tree acts as a conductor and it bursts apart burning having reached an extreme coefficient of expansion.
    Effects of man
    Lightning kills in the following techniques
    1. If a person is standing in the open then he is the tallest object around and is likely to receive a direct strike to the head with the electrons having travelled from the soles of feet to the head.
    2. If one is standing next to a tree he may represent a lower resistance than the tree and so a side flash may pass from the tree trunk to his head.
    3. Inside a hut, a man possesses a lower resistance than the mudwalls and hence rebouncing electrons strike him.
    Causes of death
    A man may be killed by a current as low as 220 volts no wonder why people may be electrocuted by the domestic mains.
    1. When current from lightning passes through the brain particularly the respiratory centre at the back of the neck, respiratory centre at the back of the neck, respiratory failure occurs and breathing stops, the heart might still be beating and a quick certifical respiration may save life.
    2. When current passes through the heart, the pumping muscles may be disturbed or damaged causing to the stoppage of blood circulation which is oxygenated. Death occurs within minutes unless the heart is push started by means of a hard chest punch.
    3. When the strike hits a hut some people might be shocked and become unconscious then get burnt when the hut catches fire.
    4. Touching a charged object like a fence, metal tools and others may cause severe to fatal electronic shocks.
    Mans' benefits from lightning
    If only man could harness lightning then Africa especially could have been far ahead of the world in technology. Fields could be cleared of forests without any cost. Man could also be blasting granite for sale and open cast mining could have been in the hands of those with the arsenal. Nature however has been able to regenerate itself by means of lightning.
    1. Lightning fixes nitrogen into the atmosphere by burning atmospheric nitrogen and mixing it with oxygen.
    2. A lightning flash releases fixed nitrogen from the air, and every year millions of tonnes of this valuable fertilizer are deposited on the land by thunder rains when atmospheric nitrogen is suddenly heated by a flash of lightning rendering it soluble in rain water no wander why the crops look healthier every time after a thunderstorm.
    3. Nitrogen accounts for eighty per cent of the atmospheric gases and when a flash of lightning passes or touches the atmosphere the nitrogen becomes chemically united with oxygen in the atmosphere thereby acquiring a characteristic that enables it to be consumable by plant life.
    Precautions against lightning
    1. Avoid exposing self to empty self to empty exposed places during lightning storms. If caught in a storm squart with the feet together without touching the ground with your hands.
    2. Do not seek shelter near or under isolated trees. If you shelter in a woodland, be between the trees not under the tallest.
    3. Do not stand close to lightning conductor or walk along a fence.
    4. Shelter inside a car or bus with metal all around you. A metal tin house is only safe if the floor is metal as well.
    5. Do not bath or shower in lightning storm even washing kitchen utensils.
    6. Wear shoes with rubber soles in rain.
    7. Fix lightning conductors above homes use, (4mm) conductors with the end buried one and a half metres deep in the earth. For homes a horizontal wire should be mounted at least six metres high and you will be safe
    1. Karimanzira P.R., Marsh et al 19986 Lightning Deaths in Zimbabwe.
    2. ZESA 1986 "Hut Deaths and Lightning Protection"
    3. Law-Brown DC 1983: Lightning and Protection
    Lightining, the terror of summer; understanding and dealing with it
    Bishi Chikomo writes on his own capacity and can be contacted on 0774 055 081
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