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LIGHTNING STRIKES
Read more on - Polity | Economy | Schemes | S&T | Environment
- Death by lightning: While natural disasters will continue to unleash their fury on earth, there are several ways to reduce our own risk of injury and death. In developed nations, the fatality rate from lightning has decreased, thanks largely to widespread awareness programs. For instance, in the US, only 16 people died of lightning in 2017, compared to 432 deaths in 1943.
- How it starts: The formation of a thunderstorm involves rapid movement of air at low temperatures, the cloud particles becoming charged in the process. Negatively charged particles gravitate to the bottom half of the cloud. At the same time, opposing charge builds up on the ground far below. Because air is a poor conductor of electricity, initially nothing happens, and electrical charges continue to build up further. This can be likened to the gradual stretching of a rubber band.
- And then it breaks: Just as a rubber band that is slowly getting stretched will break abruptly in the end, the attraction between the opposing charges eventually overcomes the air resistance and the charges rush towards each other completing the electrical circuit. This massive spark of electricity is seen as lightning. In addition to cloud-to-ground lightning, it is also common for lightning to travel between clouds—this is called cloud-to-cloud lightning. Occasionally, it can travel upwards from tall structures on the ground to the clouds.
- What is thunder: The sudden discharge of electricity in the form of a streak of lightning heats up the adjacent air to temperatures over 50,000 F, which is even hotter than the surface of the sun. As a result, a large number of superheated air molecules gets pushed sideways, colliding with other air molecules in the area. This generates a deafening noise, which we hear as thunderclap. The rumbling effect is created as sound waves get generated at multiple points along the length of the lightning streak.
- How dangerous: Surprisingly, although the amount of electricity discharged is massive, most people who get struck by lightning will survive. Some are left with nerve damage, others with scars on their body. As it can interfere with the electrical circuitry of the heart, a common reason for death by lightning strike is cardiac arrest. Prompt resuscitation can save such a person’s life.
- What precautions to exercise: Given ahead is a list of things to do, and not to do.
- Avoid being outdoors: Lightning is nothing but a large spark of electricity that is trying to find the easiest and shortest path to the ground. Logically, it could hit the highest point, typically an isolated tall tree, telephone pole or a person who is standing up. For example, if we are walking in an open field without trees during a thundershower, then we are the tallest structure, and could potentially become a target for lightning.
- Do not take shelter under tall trees: It is unsafe to take shelter under an isolated tall tree, as it could attract lightning and pass it on to us. If caught in a forest, it is better to be either in a clearing or near the shortest trees—these are less likely to attract lightning.
- Avoid high altitudes: For the same reason, being at a hilltop or rooftop at such a time is considered risky. If caught in such a situation, we should quickly move to low-lying areas whenever possible. Lightning travels along vertical surfaces to seek the ground, hence standing just below the overhanging edge of a cliff is also considered dangerous. That being said, for a lightning bolt that is traveling to the ground at extreme speed from a height of several thousand feet, it is unlikely that small heights such as five or fifteen feet will make any difference on where exactly it hits the ground. Experts say that the bolt can hit anywhere on the ground, not necessarily at the tallest point.
- Do not lie down on the ground: It is dangerous to lie down on the ground in an attempt to escape from lightning, as the electric charge from a nearby strike will spread horizontally along the ground.
- Avoid fences and wires: Lightning can also reach us through ‘conduction’, which is from contact with metallic objects such as a wire fence, plumbing or landline that is connected to the telephone pole. Staying away from such objects is therefore important.
- Keep those feet together: Ground current affects cattle and deer the most. This is because their feet are wide apart, creating a voltage gradient as lightning travels horizontally along the ground after a strike. The flow of current damages the heart as it enters through one leg and exits by the other, causing death. When there is threat of ground current, keeping our feet close together will reduce injury. This is because the shorter the distance is between our feet, the smaller will be the voltage difference, and the less likely that our heart will be electrocuted.
- Safest place is indoors: Most thunderstorms last 30 minutes or less, and the safest place to be at that time is deep inside a solid, fully enclosed building. It is wise to stay away from windows, avoid touching any metallic objects or wires and avoid leaning on concrete walls. Bus shelters, open sheds and tents are unsafe options.
- No landlines: It is dangerous to talk on a wired telephone (landline) during a thunderstorm, as they are directly connected to outdoor posts that might easily be struck by lightning. Mobile phones must be unplugged from their chargers. Using mobile phones is safe during lightning as they are not connected to telephone post.
- Unplug electrical devices: If lightning strikes an electric post outside, the current can travel through the wires and hit us if we are using an appliance that is plugged in to the electrical outlet. Hence, it is unsafe to operate equipment such as the electric iron during thunderstorms. At least a few people would be hopeful that surge protectors will prevent damage to electrical equipment during a lightning strike. Unfortunately, this is false. In fact, the huge blast of electricity from a lightning strike effortlessly jumps air-gaps and gets past fuses and circuit-breakers—almost as though they did not exist. So unplugging is the only certain way to prevent damage to expensive equipment such as TV or computers during a thunderstorm.
- Distance of strike: At only 343 metres per second, sound travels much slower than light. This is why we get to see the lightning first, and then hear the thunder. The longer it takes for us to hear thunder after a flash of lightning, the farther away the strike is. We can easily calculate how far away the lightning occurred simply by counting the number of seconds of delay between the flash and the sound. If we divide the delay in seconds by 3, we can calculate the distance in kilometres. For example, if there is a 30 second delay after seeing the lightning flash to hear the sound of thunder, it means that the incident occurred 10 km away (30 divided by 3).
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