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I was reading an article from abcnews about Why so many people survive being struck by lightning. Later in the article it says the following:

But direct strikes make up only a minuscule portion of all lightning strikes, said Cooper.

"The vast majority of deaths are caused by ground current, where lightning hits a distance away and then travels through the ground in all directions. And if you're close enough to the point it hit the ground, then you get an electric charge," Cooper added.

I understand that rubber shoes might not provide protection against direct lightning strikes. However would shoes with rubber soles provide any form of protection against cloud-to-ground lightning strikes (where the electrical current goes through the ground)?

Drago
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1 Answers1

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Yes, rubber shoes would reduce the amount of current that flows through your body. Here's a rough model for ground-splash: Assume the ground is flat and of uniform conductivity. With no one standing on it, lightning that hits the ground will produce a voltage on the ground $V(r)$ which depends only on the distance from the location of the strike. Wet ground is typically pretty conductive, so let's assume that the amount of current flowing through the dirt is much greater than any amount of current that might flow through your body. We can then add a human to the situation without changing the potential field much. We can model the human as a resistor of resistance $R$ with feet at locations $r_1$, $r_2$. The current that flows through you is then $$I = \frac{|V(r_1) - V(r_2)|}{R}$$ and the total power dissipated in your body and shoes is $$ I^2R = \frac{(V(r_1) - V(r_2))^2}{R}$$ Rubber shoes increase $R$, so they decrease the amount of current you carry and the amount of energy you dissipate. (Also, energy dissipated in your shoes is probably less harmful than energy dissipated in your torso). This model also demonstrates another very important lightning safety tip: Keep your feet together.

Other answers seem to assume the amount of current you carry is fixed. This might be approximately true for a direct strike, but is probably not true for ground splash. If your body has very low resistance or the soil has very high resistance, I think we can model the situation as a current divider to see that the rubber shoes still help.

Exercise for the reader: How does the resistance of your body compare to that of the dirt between your feet? Helpful links: https://en.wikipedia.org/wiki/Soil_resistivity https://pubmed.ncbi.nlm.nih.gov/10593226/

Daniel
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