It was a stormy night; the winds were howling, the trees were doing a macabre dance as they bent and swayed violently in the gust of winds. It was pitch dark, so dark you could not see your outstretched palm.
Suddenly, the whole night was eerily illuminated, and you instinctively braced yourself for the loud crack that would follow. Sure enough, the entire house reverberated from the ensuing aftermath of the lightning. You just witnessed lightning and thunder or thunder and lightning as most people call it. Isn't it odd though that lightning which comes first is placed second in most literature?
Pixabay: Lightning
What causes lightning?
Remember static electricity? It is ok if you do not, but recall that shock you get when you walk across a carpet and touch a metal doorknob. That is static electricity at play.
Our body is made up of atoms, and these atoms have negative and positive charged electric particles. But if the negatives cancel out the positive we would have the body at electrical "neutral".
But if an imbalance occurs (you have more positives than negatives or more negatives than positives) you have set yourself up for a zap when you touch a metal object, e.g. the doorknob.
The zap is merely the imbalanced charges being shared between you and the other object ( in this case a doorknob). In other words, static charges look for an opportunity to discharge.
The same static charge plays a role in thunder and lightning.
The cloud as it moves accumulate electric charges. The positively charged part of the cloud rises to the top because it is lighter, while the heavier portion of the cloud that is negatively charged sinks to the bottom.
Electrical insulation is provided by air and other dielectric materials in the atmosphere.
Wikipedia Creative Commons: Postively and Negatively Charged Cloud
But once this insulation is broken down, ZAP! Lightning occurs!
Remember the doorknob that gave you a shock when you touched it that I described earlier? It would come into play right now. The lightning here would look for a similar "doorknob" to discharge to.
A Lightning Path
The negative charge could be seen from this slowed down gif initiate descent known as the step leader. As it descends to the ground, an upward positive charge referred to as streamer could be rising.
These two channels connect to showcase a lightning strike. You can watch the animated slowed down lightning process detailing the meet between negative charge step leader and the positively charged streamer lighting here.
How strong is a bolt of lightning?
The thunderstorm creates a massive amount of electric voltage in the neighbourhood of two hundred thousand volts (200,000V) to five hundred thousand volts (500,000V) and packing between 1200 amperes to 200,000 amperes in electric current.
The temperature of the air around a lightning stroke is superheated to about 20,000-degree Celsius. That may not seem like much till you realise the surface temperature of the sun is 5,500-degree celcius.
How about the often terrifying sound that trails the lightning referred to as thunder?
As lightning follows a path that is about an inch in diameter, it superheats this air making it expand. As the air cools it contracts. Then surrounding air vibrates due to the supersonic shockwave.
Some Safety Tips During Lightning and Thunder
Outdoors are not safe during lightning.
Stay off the water. Bodies of water such as pool, beach, etc. are never a good area to stay during thunderstorms. The reasons are simple, water is a poor conductor of electricity but still a conductor.
- Try not to be the tallest object in the vicinity. Avoid seeking shelter under tall lone trees. If you stand under a tall tree during lightning, the trees are more susceptible to lightning strikes due to its pointed tip ( electric field are strongest at the tip of every conductor). But trees are not good conductor as our bodies. The lightning current may easily cross over to you and follow the path of least resistance (your body) to the ground. If out on a hike on a mountain, it is safer to head downhill. Taller objects are more likely to be hit by the lightning stroke, but that does not make you safe if you are not the tallest. For example, if a man is standing beside a 5m pole and lightning strikes at that point, the lightning would strike at that 5m pole leaving the man safe. If however, the man is standing more than 5m away from the 5m pole, there is a chance for him to be struck. This distance of five meters, in this case, is called the distance of influence and is roughly equal to the taller object.
Lightning stroke is initiated very high in thunderstorm clouds. Objects on the ground have very little influence on its travelling path, until the stroke comes to a distance very close to the ground. It is true that taller object is more susceptible to lightning because of shorter air gap between the lightning stroke and the object. However, for any attraction effect to come into play, the lightning stroke has to be very close to the object. The distance of influence is roughly equal to the height of the object. For example, a 4-metre pole can only attract lightning strokes which are less than 4 metres away. Therefore, do not assume that you are safe from lightning even if you see something else tall in your vicinity.Source: HongKong Weather Observatory
Stay off tents/open shelter as the frames are usually made of metal which is a conductor of electricity. That is also applicable to stay off objects during thunderstorms such as power lines, chainlink fences, bathtubs, sinks, etc.
Cars are safer. If caught in a thunderstorm staying inside your car is safer since the metal body of the car acts to disperse lightning to the earth. Though not entirely safe, but better than waiting outside.
This infographic has a lot of useful tips on staying safe during lightning.
