Naked Science Forum
On the Lighter Side => That CAN'T be true! => Topic started by: bezoar on 22/05/2022 00:01:00
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I just read that 90% of people struck by lightening survive. Considering that a lightening bolt I’d 50,000 degrees F how can this happen? Seems like even a second at that temperature would fry a person.
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90% of the people survived, that doesn't mean that they were feeling all that great.
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Most people who are impacted by lightning suffer due to Earth Potential Rise, which affects a radius of many meters around the lightning strike.
- This causes a high voltage between the feet, which causes a current up one leg, and down the other - avoiding major critical organs.
- The affected people can be seemingly hit at random - if both feet are equidistant from the strike, there will be no potential difference.
There is something called the "skin effect" in wires, where high-frequency components tend to stay in the outer skin of the wire.
- In the rarer case where a person is directly hit by lightning, "skin effect" takes on a dual meaning - with waveform time constants around 10μs-50μs, there are a lot of high-frequency components, and much of the current tends to flow around the skin rather than the core.
However, even in the survivors, long-term neurological problems often occur, as well as short-term problems like damaged eardrums and burns also occur.
https://en.wikipedia.org/wiki/Lightning_strike#Strikes
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Seems like even a second at that temperature would fry a person.
It doesn't last a second.
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I have a friend who has been struck by lightning twice. His only visible oddity is an amazing Afro hairstyle which he ascribes to those misadventures.
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evan_au, I can think of a couple of critical organs between the legs that might be in the path of the lightening as it travels up one leg and down the other, which then leads me to wonder if people who experience that sort of strike are rendered sterile. But my main question is how can a human body tolerate that amount of heat, even if only for a nanosecond?
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But my main question is how can a human body tolerate that amount of heat, even if only for a nanosecond?
Time is actually a very important factor here. If the exposure time is short enough, a normally fragile substance won't absorb enough heat to burn even if the temperatures are very high.
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how can a human body tolerate that amount of heat?
The human body is largely composed of water, which has a very high heat capacity.
The water is slightly salty, which makes it slightly conductive
- Probably slightly more conductive than a tree-trunk, so don't lean on a tree trunk in a storm!
- But the voltage drop across 2 meters of ionised air is very low, so some of the energy may bypass the human body (at least, in survivors)
even if only for a nanosecond?
Standard lightning test waveforms have a rise time of 1μs, and a fall time of 50μs.
So you could loosely say that the average duration of a lightning impulse is around 50μs, or 1/20,000 of a second.
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That is amazing. Seems like we see a lightening strike for longer than that. I had a patient once who was struck by lightening. Entrance wound on the head and exit wounds on them feet. Needless to say, he was not one of the 90%.
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I can think of a couple of critical organs between the legs that might be in the path of the lightening
If the Earth Potential Rise is (say) 30,000 Volts, and it dissipates over a distance of (say) 100m, that is 300 Volts per meter in the soil.
A typical pace might be 0.5m, so 150 Volts between the legs will produce an electric shock, but not anything like the voltage of a direct lightning strike.
- The ground resistance will also provide some series impedance to the current in the legs
- If you are standing, the distance between your feet might be closer to 0.2m
- If you are walking, half of the time, there will be only 1 foot on the ground (ie perhaps a small current in one foot, but nothing up the legs - and that one foot may have a plastic-soled shoe on it)
- If you are running, most of the time there will be only 1 foot on the ground
The human condition is much better than for (say) a cow. The distance between front and rear feet is more like a meter (300V in the above scenario), and there are some very electric-sensitive organs between these locations, like the heart and spinal cord.
- Most of the time, cows have at least 2 feet on the ground, and no shoes
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According to a book on aerial design and practical implementation for low frequency systems(which disappeared in a liquidation-I can't even remember it's name), lightning can produce currents of up to a max of 175ka. This was rather old and I would imagine this was before the recognition of positive strike lightning. According to Wikipedia positive strike can go as high as 400ka and it's duration is longer. I wouldn't fancy that at all. I have had a few close shaves when working on transmission towers and as a result i'm scared of lightning. In the states most lightning casualties involve landline use and are most likely not direct strikes.
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Hello, I'm from Barcelona, and I was struck by lightning on top of a mountain 6 years ago, I don't know what % i entered, but it entered through my head and came out through my feet or vice versa, nobody knows what order it had The fact is that i suffered deep 2nd degree burns throughout torso, head and both feet, in addition to bilateral rupture of the 2 eardrums that today after 3 failed operations are still open. Also cranial hemorrhage and broken cheekbone due to impact with a rock after lightning.
The question is not how it is possible for people to survive lightning, because as they have said, there is a high survival rate.
The problem is the late side effects derived from this event, especially neurological ones.
Balance problems and dizziness, severe migraines, deafness, memory and concentration problems, cataracts, dry eyes, etc.
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For me it's not weird that they survive but the fact that there are so many people on earth who get struck by lighting multiple times. I think this is crazy