The good news is that the chance of being struck by lightning this year is less than one in a million. Even better news is that 90% of people struck by lightning survive. Even so, it is always advisable to avoid risks when we are talking about atmospheric phenomena as violent as these.
Lightning strikes cause both fear and fascination, a fascination that sometimes leads us to ask questions about the nature of these immense electrical columns.
What is lightning
Lightning is an electrical discharge (each lightning can generate several discharges), generally of very high power, that occur in clouds. These are meteorological phenomena that, although they have its origin in the atmospheresometimes they reach the surface of the Earth.
We usually associate lightning with storms and cyclones, but these discharges can occur in other contexts, for example during volcanic eruptions, during fires of a certain intensity or when nuclear weapons are detonated.
How lightning is formed
Lightning usually occurs in stormy conditions and, the truth is that we do not fully know how. We know that under certain conditions, clouds can go accumulating electrical charges both positive and negative. In these cases, the air acts as an insulator between areas of positive or negative accumulation, as well as between these areas and the Earth.
At a certain point, the accumulation of these charges exceeds a threshold that causes this insulating capacity of the air to give way. So all that accumulation of charges generates an electric current capable of traveling long distances (even several hundred kilometers). The discharge allows the electrical charge to balance, but the charges can accumulate again until the next lightning strike.
What remains a mystery to us is the beginning of this process, how positive or negative charges accumulate in certain regions. The main hypothesis suggests that the origin of this accumulation is in tiny hail particles (also called graupel) that grow as they encounter supercold water droplets (in a liquid state but with temperatures below freezing).
In thunderstorms, these icy particles would frequently collide, colliding with other icy particles. These collisions would cause the charges of the different particles to gain charge of one sign or another.
Difference between lightning, thunder and lightning
Electrical shocks are usually invisible to the human eye and they also do not generate noise, but this is not the case with lightning. Lightning generates not only a flash of intense light, but also a significant roar.
We call the zigzag luminous path of lightning lightning. As it passes through the atmosphere, the electrical discharge causes the air to heat up to exceed temperatures of 27,000º Ceslius, a temperature higher than that observed on the surface of the Sun. This causes the air to become incandescent, generating lightning.
Such rapid and intense heating of the air has another effect, making it “explode” outwards. This rapid movement of air is responsible for the second element that makes up lightning, sound or, in other words, the thunder.
Light and sound move through the atmosphere at very different speeds. This is what makes us see lightning even seconds before its sound reaches our eardrums. This gap gives rise to an old trick to measure the distance at which the storm is from us. If we count the seconds of lag between light and sound and divide the result by three, we can estimate the distance in kilometers at which the lightning occurred.
Types of lightning
Cloud flashes and cloud-to-cloud
Among conventional rays we can distinguish various types depending on the location of the points they join. The first of the groups that we can distinguish is that of the cloudy flashes. Most lightning strikes never reach the ground, in fact it is common for them not to even escape the cloud in which they occur. These rays are also often called intra-cloud rays.
Within the category of lightning that never reaches the ground, there are some whose path partially escapes the cloud and even some that start in one cloud and reach another different cloud.
Cloud-to-surface
We distinguish these cloudy flashes and rays from those that do manage to reach the Earth’s surface. These types of discharges occur from the top down, at least when they happen naturally.
The rays that join cloud and surface can be both negative and positive depending on where the respective negative and positive charges are located. Negative rays are the most common rays (they represent around 95% of impacts). In these rays, the clouds accumulate a negative charge and the Earth has a positive charge. When lightning opens the channel, the negative charge moves from the cloud to the ground, hence the name.
The positive rays They are less frequent but at the same time more powerful. The reason is that these originate in higher areas of the cloud, so they must travel further. This in turn means that they accumulate more energy before discharging.
Other unique events
However, there is a different category that we call transient light events, or TLE (transient luminous events). These phenomena are much less frequent, more difficult to observe and, as a consequence, much more mysterious.
How powerful is lightning?
The strength of lightning can vary considerably depending on atmospheric conditions and the Earth’s surface. As explained According to the United States National Weather Service, a “typical” lightning strike can discharge about 30,000 amperes with 300 million volts.
However, we pointed out before that a positive ray can transport much more energy. According to NOAA (National Oceanic and Atmospheric Administration), the organization on which the American meteorological service depends, these types of discharges can be an order of magnitude higher, discharging 300,000 amperes with 1,000 million volts.
Many will wonder Why don’t we take advantage of this energy? and the answer is that, today, there are too many difficulties to make this technology a reality. First, we must keep in mind that lightning is a transitory phenomenon that can occur in different places: to obtain its energy we would have to move towards the storm.
Secondly, this impermanence and uncontrollability means that we could not simply let the discharge flow into the electrical grid but would have to store it and then use it in a controlled way. To do this we need adequate and much more resistant equipment than what we have today: the enormous power of the discharge, which could “fry” many of the devices that we should use to capture these discharges.
Image | Dmitry Zvolsky
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