Each year, the average number of people injured from lightning strikes in the US is around 243, with roughly 27 people dying as a result. With a peak temperature of 27,760°C (50,000°F) – that’s nearly five times hotter than the surface of the Sun – it is, unfortunately, unsurprising that lightning can be so deadly, but what is really happening to the human body when lightning strikes?To understand the effects of lightning strikes, we first have to understand what causes them to occur.How does lightning form?Lightning forms as a result of warm air rising and cooling to make small droplets of water that eventually form a cloud. If warm air continues to rise, these droplets combine to make larger droplets that eventually freeze to become ice crystals. As these ice crystals grow, they become too heavy to be held in the cloud and can fall to the ground as hail.As growing hail stones move around the cloud, they become negatively charged by rubbing against smaller positively charged ice crystals. As the hail collects at the base of the cloud, this area becomes negatively charged, while the lighter ice crystals remain at the top of the cloud with a positive charge.The particles with negative charges are attracted to the Earth’s surface. “Grounding objects” like trees and other tall, conductive structures reduce the distance between the negatively charged particles and the Earth’s surface, making them vulnerable to being struck. When the attraction becomes too strong, the positive and negatively charged particles discharge causing a strike of lightning. The lightning causes a rapid expansion of heat and air, which causes a loud clap of thunder.According to The Met Office, it’s estimated that lightning strikes the Earth approximately 44 times every second with nearly 1.4 billion lightning strikes annually. While rare, lightning striking humans is thought to injure around 240,000 people and kill 24,000 people each year worldwide.Lightning strike injuriesCarrying 10 million volts of energy (for reference, powerlines carry around 100,000 volts), lightning strikes can cause serious damage to most systems within the body. The most commonly affected areas are the circulatory, respiratory, and nervous systems.While lightning strikes can cause brain hemorrhaging, strokes, and deep tissue injuries, the most reported deaths occur as the result of cardiac arrest where the strike’s current has disrupted the natural rhythm of the heart. Counterintuitively, administering another electric shock with a defibrillator after someone has been struck by lightning may increase their chances of survival.Lightning strikes can also cause the respiratory system to become paralyzed as a result of the strong current. To avoid suffocation, artificial respiration is required.Damage to the nervous system can often lead to keraunoparalysis – a temporary paralysis that affects the lower limbs – as well as impaired reflexes and ongoing neurological symptoms like depression and anxiety.Blown eardrums, damage to the eyes, and burns on the skin are also common due to the intense sound, light, and heat that can cause clothes and hair to catch on fire. For those who survive, it’s estimated that 74 percent suffer some form of long-term disability, with brain damage causing changes in mood and memory, and nerve damage causing chronic pain and mobility issues.While experts aren’t entirely sure what causes neurological issues from lightning injuries, it’s thought to be a result of the current causing tissue damage in the brain and the effects of blunt force trauma caused by the abrupt pressure change.“Lichtenberg figures” are also a rare side effect of lightning strikes. Created when electrical discharges pass along the surface of the skin or through insulating materials, Lichtenberg figures, or “lightning flowers”, create intricate tree-like patterns on the skin. They’re thought to occur as a result of fluid leaking into the surrounding tissue from damaged blood vessels.Types of lightning strikeThe effects of being hit by lightning can differ depending on the type of strike that impacts the victim. Categorized into five variants, some lightning strikes can be significantly more common, and more deadly, than others.Direct strikes are the least common, making up between 3 and 5 percent of strikes, but the deadliest. During a direct strike, part of the current passes through the body and part passes over the skin’s surface (called flashover). While flashover causes burns to the skin, the current that passes through the body causes the most serious damage as it travels through the cardiovascular and nervous systems. This strike tends to occur to victims who are standing in open areas where their body is the main lightning discharge channel.Side flashes, also called a “side splash”, occur when a taller object near the victim gets struck and a portion of the current jumps from the object to the person, “short-circuiting” the current. This strike tends to occur when a person has taken shelter under a tree or other large object and is within a foot or two of it.Ground currents occur when an object or the ground is struck, the current continues to travel along the ground’s surface, so anyone outside in the vicinity of a strike is at risk of being affected by the ground current. The lightning enters the body at the contact point closest to the strike point and travels through the body, exiting at the contact point furthest from the strike. The larger the distance between the contact points, the more severe the injury, making larger animals more at risk of death through ground currents. As they can affect multiple individuals at once, ground currents are one of the most common causes of lightning injury and cause the most lightning deaths. Side flashes and ground currents together make up 80 percent of lightning trauma cases.Conduction accounts for around 5 percent of lightning injuries and can affect people both inside and outside the home. They happen as the result of lightning striking something metal. While metal does not attract lightning, if it picks up any of the current from a strike it can conduct it for as long as the metal chain goes uninterrupted. This means people can be shocked through metal fencing or even a building’s plumbing and electrical systems.Streamers account for the remaining 10-12 percent of cases and can cause death and serious injury. Streamers occur when positively charged electrical forces on the ground become attracted to the negatively charged currents in the storm clouds. As the clouds release a “leader”, it typically approaches the ground and is met by a streamer to form a lighting channel. When a leader is discharged, however, all the surrounding streamers will also discharge, and if a person is part of one of the discharged streamers they can be killed or injured regardless of whether the lightning channel was completed between the streamer and the cloud.        A 2020 report also found that men make up a larger percentage of lightning strike victims, speculating that men “are unwilling to be inconvenienced by the threat of lightning, are in situations that make it difficult to get to a safe place in a timely manner, don't react quickly to the lightning threat, or any combination of these explanations.”The report looked at lightning deaths in the US between 2006 and 2019, of which there were 418 cases. Despite the common belief that golfing is the activity that puts you most at risk of lightning strikes, the report stated fishing is actually the deadliest activity with 40 deaths, followed by being at the beach, camping, and boating. Men accounted for 79 percent of all fatalities and women had fewer deaths than men in every category.For most people, there’s only a roughly 1 in 1.2 million chance of getting hit by lightning in any given year in the US, but not for ex-park ranger Roy C. Sullivan of Virginia, USA. Sullivan is the only known person to be struck by lightning seven times, between 1942 and 1977, and he survived each one.To stay safe from lightning strikes, remember that if you can hear thunder you’re probably in striking distance. Keep low, avoid tall objects, and get inside a building or car.

Five hundred million years ago, the Earth was a whole lot of sea. Underwater, the Cambrian Explosion was bringing a flurry of differentiation that laid the foundations for modern animal phyla. The new creatures were not just multicellular blobs, but had many of the distinguishing features of animals today: eyes, legs, shells, and mandibles. One of these creatures appears to have been not only a pioneer in body shape, but also in lifestyle. It has been called a submarine and a taco, but its name is Odaraia alata.Odaraia had been first found 100 years ago in the Burgess Shale, a rich fossil deposit in the Canadian Rockies. It contains some of the oldest fossils of soft body parts (500 million years old!), providing many insights into what the Cambrian world looked like.Most Cambrian animals were part of the benthos, the ecosystem of the seafloor, but Odaraia with its 20-centimeter (7.9-inch) long body may already have been swimming up the water column – to hunt. By studying 150 fossils of Odaraia, Alejandro Izquierdo-López and Jean-Bernard Caron could create a detailed reconstruction of what this arthropod would have looked like, and how it probably fed.“The head shield of Odaraia envelops practically half of its body including its legs, almost as if it were encased in a tube,” said lead author Izquierdo-López in a statement. Its taco-like appearance is only one of the remarkable features of Odaraia. Of particular interest to the researchers are its mandibles and the many spines along its body.In this fossil, Odaraia reveals her taco shell.Image credit: photo by Jean-Bernard Caron, Royal Ontario Museum.Mandibles are ubiquitous in the world today, with almost half of all species having them, but they were a rarity in the Cambrian. The mandibles of Odaraia appear lined with teeth, and with divots for the muscles to attach and control them. This evidence secures Odaraia a spot among the pioneers of this body part.Even more useful in prey-capture than the mandibles are the spines. Along the length of the body of Odaraia, the researchers found 30 sets of legs with small spines that could have created a mesh to capture prey with. This suggests that Odaraia could have been a suspension feeder, capturing prey similar to mesozooplankton in the net of its spines and then moving it to its mouth.Oh, and they also found that Odaraia had a tooth shaped like a trident at its mouth opening. They suggest this resembles a gastric tooth, which amazingly is a tooth that lobster and crabs have inside their stomachs.The authors highlight “the role of recovering anatomical information to improve ecological reconstructions”.This study is published in the Proceedings of the Royal Society B: Biological Sciences. 

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