# Lightning's Lethality

## Main Question or Discussion Point

Does anybody know why lightning doesn't kill any living thing it touches if it is supposed to be four or five times hotter than the sun and has a huge amount of voltage? The heat alone should be able to kill living things instantly, right?

Related Biology and Medical News on Phys.org
ZapperZ
Staff Emeritus
Does anybody know why lightning doesn't kill any living thing it touches if it is supposed to be four or five times hotter than the sun and has a huge amount of voltage? The heat alone should be able to kill living things instantly, right?
Wait, what? There have been reports of people killed by lightning! What do you mean that it doesn't kill any living thing it touches? Where do you get such an idea?

Zz.

berkeman
Mentor
I think (but am not sure) that he is asking how come it doesn't *always* kill whatever it strikes.

If so, it just depends on how much of the current goes through the critical parts of the body (brain and heart). If for some reason most of the current bypasses the person's core (or animal's core), then they may survive the strike...

I think (but am not sure) that he is asking how come it doesn't *always* kill whatever it strikes.

If so, it just depends on how much of the current goes through the critical parts of the body (brain and heart). If for some reason most of the current bypasses the person's core (or animal's core), then they may survive the strike...
Yes, that is what I meant. Sorry for not phrasing the question right.

I get what your saying. I was wondering the exact process though. I understand that all the current doesn't travel through the body, even with a direct hit by lightning, but if the lightning is so hot, that should be independent of the current, right? The heat should have exploded the water inside your body the same way it explodes clothes outside the body and inside trees, destroying them.

Unless when they say that the temperature of a lightning bolt is five times the sun, they really mean that it has the potential to reach five times the heat of the sun if the current is allowed to move freely through whatever it touches.

Just trying to sound it out, but when I think about it a lightning strike is not that much more lethal than a gunshot unless the survivors simply aren't ever hit by a direct lightning bolt. That would explain some things.

Pythagorean
Gold Member
Just like if you take a blow torch to your hand, it doesn't kill you, it demolishes your hand. With lightning, the heat only spikes where the current travels, so of it doesn't hit vitals, it's less likely to kill you.

Lightning can take different paths depending on where it finds ground, or the lowest potential path.

Evo
Mentor
Damage to the human body:
Lightning affects the many electrochemical systems in the body. People struck by lightning can suffer from nerve damage, memory loss, personality change, and emotional problems. There is a national support group for lightning and electric shock survivors.

An example is some single nerve cells, such as those extending from the brain to the foot, can be as long as 6 feet or more. These types of cells are most prone to lightning damage due to the instantaneous potential difference across the length of the cell as lightning begins to enter the body.

The intense heat of the lightning stroke can turn sweat instantly to steam and the tremendous pressure of the steam has been known to blow people's boots, shoes, and clothing off them. In places where metal is in contact with or close proximity to the body, such as jewelry or belt buckles, burn marks are found. Likewise, burn marks are found in places where the body had been sweaty, such as the feet, underarms, and chest.
http://www.nssl.noaa.gov/primer/lightning/ltg_damage.html

I read through that link and it instructs to take safe shelter, but it doesn't really describe safe shelter.

If I'm up on a mountain, what should I do to be safe? It says stay away from trees, but I know you also don't want to isolate yourself.

I know from a physical perspective, lighting will strike the path of least resistance. Air has a very high resistivity compared to most solids/liquids, so being higher up is therefore dangerous. I'd guess that human resistivity is lower than that of wood, or rock, so you'd need to be significantly lower than the surrounding wood/rock, so that your elevation difference will outweigh the lower resistivity of your body.

Evo
Mentor
I read through that link and it instructs to take safe shelter, but it doesn't really describe safe shelter.

If I'm up on a mountain, what should I do to be safe? It says stay away from trees, but I know you also don't want to isolate yourself.

I know from a physical perspective, lighting will strike the path of least resistance. Air has a very high resistivity compared to most solids/liquids, so being higher up is therefore dangerous. I'd guess that human resistivity is lower than that of wood, or rock, so you'd need to be significantly lower than the surrounding wood/rock, so that your elevation difference will outweigh the lower resistivity of your body.

For example that page links to this one for safety.

Level-3: When lightning threatens, go to a safer location. Do not hesitate. The lightning casualty lore is replete with tales of persons just about to make it to safety when they were struck. Even a few extra minutes lead time can be life saving.

What is a safer location? The safest place commonly available during a lightning storm is a large, fully enclosed, substantially constructed building, e.g. your typical house, school, library, or other public building. Substantial construction also implies the building has wiring and plumbing, which can conduct lightning current safely to ground. However, any metal conductor exposed to the outside must not be touched precisely because it could become a lightning conduit. Once inside, stay away from corded telephones, electrical appliances, lighting fixtures, ham radio microphones, electric sockets and plumbing. Don’t watch
lightning from open windows or doorways. Inner rooms are generally preferable from a safety viewpoint.

If you can’t reach a substantial building, an enclosed vehicle with a solid metal roof and metal sides is a reasonable second choice. As with a building, avoid contact with conducting paths going outside. Close the windows, lean away from the door, put your hands in your lap and don’t touch the steering wheel, ignition, gear shifter or radio. Convertibles, cars with fiberglass or plastic shells, and open-framed vehicles are not suitable lightning shelters.
continued...

http://www.ametsoc.org/POLICY/Lightning_Safety_Article.pdf

I've often wondered this too why lighting doesn't kill you with the heat if nothing else. My guess is that perhaps this is the temperature directly on the lighting arc itself. Air has very high resistance, people have less resistance so not as much heat would be generated passing current through you.

Also air is very low density so it may burn you where the lightning hits you but it would dissipate quickly like tin foil coming out of the oven.

I think I've heard people indeed do have burn where the lighting goes in and out which would make sense.

Also I've read they're often burnt where they had moisture on their bodies from the moisture vaporizing. While it burns them it also probably protects them from more serious injury by throwing off the heat.

It reminds me of trying to strike an arc with a stick welder and sticking the rod the arc strike instantly melts the metal and sticks the rod and the base metal together. If you leave it there for a couple seconds it'll get hot from the current flow but not that hot because the real heat comes from the current passing through the air gap between the two metals.

Evo
Mentor
I've often wondered this too why lighting doesn't kill you with the heat if nothing else. My guess is that perhaps this is the temperature directly on the lighting arc itself. Air has very high resistance, people have less resistance so not as much heat would be generated passing current through you.

Also air is very low density so it may burn you where the lightning hits you but it would dissipate quickly like tin foil coming out of the oven.

I think I've heard people indeed do have burn where the lighting goes in and out which would make sense.

Also I've read they're often burnt where they had moisture on their bodies from the moisture vaporizing. While it burns them it also probably protects them from more serious injury by throwing off the heat.

It reminds me of trying to strike an arc with a stick welder and sticking the rod the arc strike instantly melts the metal and sticks the rod and the base metal together. If you leave it there for a couple seconds it'll get hot from the current flow but not that hot because the real heat comes from the current passing through the air gap between the two metals.