Lightning: The Misery Causing Mystery

 
Descending like a silvery stream from the dark heavens, lightning surely is an alluring view to behold. Yet, from the very beginning of life, humans have always feared this phenomenon,knowing the grave dangers concealed in it. Thus, it’s of paramount importance that we take proper measures to avoid the undesirable consequences of lightning strikes.

Therefore, in order to give you a proper understanding about lightning, we thought of unfolding its consequences and means of safe guarding against it, through an interview with one of the most reputed high voltage specialists in Sri Lanka, Emeritus Professor J. R. Lucas of the University of Moratuwa, Sri Lanka.

Professor, let’s start from the very basics. Could you please tell us what lightning really is?

Okay… If you go down to the very basics, it is a huge discharge.Have you heard that small pieces of paper get attracted to your comb after combing your hair, especially when the air is dry? That is due to the electrostatic charges piling up in the comb due to the rubbing action.

The same scenario occurs within thunder clouds due to air movement and charges building up inside the clouds. When the field increases beyond a certain value, about 10kV/cm, then a discharge can occur. Most of the time, these discharges take place within the cloud (a cloud, by the way, is normally few kilometers thick), between clouds or just to the air. Only about 10% of these come to the earth, and that is the lightning we are afraid of. Most lightning occurs from the negative charge centers towards the bottom of the cloud. 

Does lightning occur only during rains? 

Well, lightning and rain are not necessarily related, but in a tropical country like ours, lightning normally occurs during rain, especially when it originates from the lower part of the cloud. 

In rare instances, the thunder cloud may be a few kilometers away and you may still find that lightning occurs from those far away clouds, which you may not see.

Have you heard of the expression “lightning from the blue”? 

As a cloud is normally a few kilometers thick, when the positive chargers at its top causes lightning discharges, then it might come from fairly far away, and you may not be able to see the cloud, and you might think that the lightning is coming from the blue sky without clouds. Then again, keep in your minds that not all rain clouds cause thunder.

Sir, lightning strikes are dangerous and that’s a well-known fact. But why?

(Making a serious face)

The main reason why lightning is dangerous is due to the enormous amount of energy that it carries. You may be able to light your room lamp for a whole year from the energy of one lightning strike: And, this energy is dissipated within a small fraction of a second. Thus, the currents encountered can be of the order of twenty thousand amperes and higher, while the temperatures can be even hotter than the sun. These alone make lightning a very dangerous phenomenon.

Moreover, once lightning strikes the ground somewhere, currents start to flow through the ground, like the roots of a tree. This gives rise to a potential difference on the surface of the ground. So, if you keep your feet apart, then a potential difference (i.e. a voltage) may appear between your feet, which in turn may cause currents to flow through your body. This can be lethal. This is illustrated in the figure.

Therefore, not only a person directly struck by lightning, but people in the vicinity could also be killed. This adds to the gravity of lightning strikes. The picture obtained from the internet shows many cows dead under a tree, due to the ground potential rise caused by lightning.

On average, how many deaths are caused by the lightning strikes in Sri Lanka?

Well, that’s not an easy question to give an exact answer. Sometimes, unless directly stuck, one may not know that someone was killed by lightning, especially if he was working in the field. People might even think that he got a heart attack. So, these kinds of deaths are not reported and facts are not available. According to records, around 40-50 deaths are reported to occur every year. Including the unreported ones, it is estimated that about 70 people die per year due to lightning in Sri Lanka.

Professor, not everybody gets struck by lightning. So, based on years of your experience, can you conclude the individuals who are more susceptible to lightning strikes?

First and foremost, you must understand that normally, the probability of being hit by a lightning strike has no direct relationship with individuals as such. Anybody is susceptible to lightning strikes, depending on various facts. 

If you are the tallest object in an open field, then you are more exposed to lightning because of the higher field. That is why farmers working in paddy fields, fishermen sailing in the sea and rangers wandering in open areas, become common targets of lightning strikes. So, try to avoid open areas when there is thunder.

 

Most importantly, if there’s only one tree in an open land, never go under it for shelter, because that is the most likely place to get struck by lightning. If the tree is struck, the potential of it increases and from the tree, flash-overs might occur putting you at a grave danger.

Moreover, the use of electrical appliances, though maybe safe, is not encouraged when lightning activity is high. Because, during lightning, the potential of the plug point might go up, and anybody touching the outer metallic part of an electrical appliance might experience an electric shock. 

Sir, if we are in an open field during thunder, and if the field is so large such that there’s no place to run to, then what can we do to save ourselves?

In a such a situation, what you can do is to position yourself such that the effects of lightning on you is minimal.

Try to reduce contact between your feet and the ground as much as possible - keep your feet touching each other at the heel. Crouch down, lower your head and body as much as possible and cover your ears from hands.  Once you are crouched down, you might not be the tallest object around. As you are keeping your feet touching each other, the voltage difference between them are minimal (step voltage reduces and the effect from the currents running along the ground can be reduced). A lightning discharge normally encounters a considerable amount of sound. By covering your ears, the harm done to the ear drum can be reduced to a minimum.

Never lay on the ground in order to reduce your height, because that’s probably the worst thing that you can do. As the contact area with the ground goes high, so does the currents flowing through your body.

What is the safest place to stay when it is lightning?

(Thoughtfully) 
A fully enclosed metal box I might say. You are quite safe there from lightning strikes, but soon will suffocate to death and it will turn to a metal coffin.(Laughing)

(Making a serious face)

Well, my advice is to stay within a well constructed building. But make sure that you are not near to open doors, windows and not in the open areas such verandahs, balconies or courtyards.  If you cannot find a building, then the next best would be a metallic vehicle.

Some think that vehicles are much safer than buildings, because they are on top of rubber tires, which is a misconception. If lightning could have come a few kilometers from clouds, few inches are not going to make any difference.  The tires in fact help to retain charges on the vehicle body. However, fully covered metallic vehicles act as “Faraday Cages” and prevent us from being struck by lightning strikes. However, if you sit near to a window, you might experience some effects of the lightning flashes that may penetrate some millimeters in the non-metallic portions.

Most importantly, you must avoid getting in or out from a vehicle, when the lightning activity is high. This is because, the vehicle can be charged to a higher potential due to lightning and can be discharged through your body when stepping in or out. So, if you are in a vehicle, wait till all the lightning is over before you step out. If it’s urgent to come out, jump off the vehicle with both feet, without touching any part of the vehicle and be mindful not to step out one foot at a time.

Containers are said to be safe, for the same reason as that of vehicles. But practical containers, where people usually stay inside, such as those you find in construction sites, have large openings for ventilation. While containers, being metal structures, attract lightning strikes, there might be flash-overs at the openings unless a metal mesh is connected across openings. So, my advice to you is to even avoid a metal container if a substantial building is available close by when there is thunder.

Is it okay to use mobile phones and land phones when it is thundering?

When it comes to lightning, mobile phones and land phones behave very differently.

The use of land phones is not advisable as surges can come through the communication wires and harm you. However, it’s quite safe to use a mobile phone, if you do not go to the verandah or other open area to getter better reception, or it is not plugged in to a socket outlet for charging.

Sir, can we use a laptop during lightning?

Of course you can! But make sure that you have removed its power, network or any other cable. If

In short, you can use normal household appliances during lightning, as long as they don’t have any wired connection to the electricity or communication networks. That means if they are supplied by batteries.

you want to connect to the internet, use a dongle.

Professor, all this time you emphasized that we must make sure our appliances do not have wired connections, if we are using them during lightning. What is the rationale?

A good question!

Power lines and communication lines are prone to lightning strikes. Even if they are not directly struck, lightning can induce surges in them. These surges travel along these lines and eventually reach electrical equipment to harm them as well their users.

Many people think that their equipment are safe as long as they are turned off. But that is wrong.  Lightning can harm even these equipment as long as they are wired to the power or communication networks.

So, make sure that your electric appliances are disconnected at the socket outlets and no network cables are connected, if you are using them when the lightning activity is high.

Professor Lucas, we could learn quite a lot of interesting facts about lightning. Thank you very much for your cooperation!

So, this marks the end of the first part of our interview with Prof. J.R.Lucas.

Keep in touch with us to discover many other interesting facts related to lightning.

Interviewed and presented by:   

Dilini Darmawardana
Himali Lakshika
Nisala Amarasekara

Watch Lightning strikes footballers

Posted in: Utility and Social