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Lightning is one of nature’s most powerful energy sources. Anyone who has ever spent time in Johannesburg during South African summer knows that there is nothing more spectacular than a Highveld thunderstorm at night. petrichorTorrents of cooling rain, thunderous booms and great lightning bolts across the sky.
These storms are awe inspiring – but also dangerous to people, animals and the built environment. African countriesSome of the most deadly lightning deaths in the world are occurring in Zambia and Uganda. More than 200,000 people have died in South Africa from lightning strikes. 250 people are killed by lightning annually.
The exact number of deaths isn’t clear, due to under reporting, but estimates from 28 countriesAccording to some estimates, there are as many as 24,000 lightning deaths per year in the world.
Deaths can’t always be definitely attributed to lightning because, while its marks are easy to spot on the skin or in the organs, nobody was sure how to identify its marks on skeletonised remains.
This is what our research shows. Our studyPublished in the journal Forensic science International: Synergy. It represents collaboration between specialists from the universities of the universities of the universities in forensic anthropology. WitwatersrandSouth Africa NorthumbriaThe UK, and the Nuclear Energy Corporation of South Africa.
This can help forensic teams determine if people or animals were struck by lightning. It is based on only their skeletons. This can be used to ascribe accidental death in cases that are not obvious and give experts a better understanding of the true incidence of lightning fatalities.
Cause and effect
When a lightning death is suspected, forensic pathologists determine cause of death by looking for signs of lightning trauma in the deceased’s skin and internal organs.
The enormous electrical current can cause neurological damage and cardiac arrest as well as respiratory arrest if a body is struck. The electrical current can cause severe burns on the soles of your feet and ears, bone fractures, and ear drums and bones to burst. Lightning can also create unique marks in the skin called “Lightning Markers”. Lichtenberg figures. These are branching patterns that look like ferns and are caused by electrical damage to the superficial blood vessels of the skin.
However, when a skeletonised corpse is recovered, there are no soft tissues. Lightning cannot be confidently attributed to the cause of death.
Our research began with a simple question about cause and effect: Does lightning leave recognizable traumatic traces or characteristic lesion when it passes through the skeleton. Were unidentified human remains found in the South African bush able to determine if they were victims of a fatal lightning strike?
The laboratory then produced artificial lightning, which was applied to bone samples taken from donors who had died naturally.
Lightning physicistsSet up a high-current impulse generation in our lab at Wits Medical SchoolThese could deliver up 15,000 amps to your bone in just a few seconds.
This allowed us to simulate the effect of lightning passing through a skeleton by creating high impulse currents. Natural lightning can have much higher current levels than artificial lightning, but this experimental setup allowed us to control the flow of electricity better than trying to place human tissue in the path.
Nicholas Bacci, School of Anatomical Sciences, University of the Witwatersrand, Hugh Hunt, Johannesburg Lightning Research Laboratory.
Imaging lightning damage
After the current was applied, we cut into the bone and imaged it with optical microscopy using micro-CT. We saw a pattern of damage that was caused by lightning currents passing through its cells.
Cracks that radiate out from the bone’s centre or jump between cells in irregular patterns were the result of this damage. The overall pattern of damage was quite different from other high-energy traumas like burning in fire.
We observed the same pattern in trauma in animals that had been struck by natural lightning. We compared human results to bone from a wild giraffeIt was well-known that the strike was accidental. The damage pattern was identical, even though human bone has a micro-structure very different from giraffe bones.
Patrick Randolph-Quinney, Forensic Science Research Group, Northumbria University and Tanya Augustine & Nicholas Bacci, School of Anatomical Sciences, University of the Witwatersrand.
The smoking gun
What was the mechanism that caused these microfractures to form in the first place? We believe there are two possible causes of this damage, either in isolation or in combination.
Firstly, the current generates a high pressure shock wave when it travels through bone. This is what lightning experts call barotrauma. It’s when electrical energy literally rips apart bone cells.
Secondly, bone reacts strangely to an electric field. This phenomenon is called a piezoelectriceffect. Collagen, an organic component of bone, can be arranged as fibrils or fibers. When a current is applied, these fibrils reorganize themselves, which causes stress to build up in the mineralised or crystallised bone. This can lead to deformation and cracking.
Both of these mechanisms would lead to fractures. This unique pattern of microtrauma was what we were looking at.
Our research provides a new tool for studying lightning fatality in real-world criminal cases. Global climate change is a pressing issue. may be driving increasesThis tool could be useful in investigating the causes of death by monitoring the intensity and number of lightning strikes and thunderstorms.
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