I had an acquaintance refer to crouching to prevent being hit by lightning. Now, my opinion is, “If you can see it, it’s already missed you,” but back to the question. . .
He said that by crouching and standing on one foot, you are safer than standing fully erect on both feet. I understand that higher objects are better targets, but I don’t get the “one foot” part. A cursory Google search indicated a question where they mentioned “step potential,” and that standing with the two feet together is safer, but anyway. . .
What is the physics (if any) behind being safer having both feet together or only standing on one foot when you’re the target of a lightning strike?
Lightning can cause severe exit wounds. I suppose the theory is that if you were to rest on both feet you might lose both feet, but if you rest on only one, you’d lose only one. See here which, though electrical and not an actual lightning strike mentions 7" exit wounds.
I was taught to lie down flat or simply crouch down with my head between the knees. The idea being that if struck, the lightning would enter at my shoulders and pass directly to my lower legs bypassing the brain and the heart.
I think this is confusing some good advice about downed power lines. If you find your self near a down power line, you want to keep you feet as close together as possible, because the potential difference from one foot to another could be enough to kill you. I don’t know if this has ever happened, but it makes sense.
Lightning causes a massive electrical gradient in the earth, starting at the strike point and radiating out. This gradient (depending on earth resistance) can vary by thousands of volts per metre, and can cover a wide area. So if your feet are wide apart, the voltage difference between the two can allow a massive voltage to flow via your body between the two points - zap.
Feet together, guys. And crouched down, to minimise the vertical gradient (though that is in air and not as bad). Don’t lie down, though.
This would be the aforementioned gradient, which exists in the earth in the area around a strike. If you’re lying down, and lighting strikes anywhere near you, the top and bottom of your body might be at vastly different potentials within the gradient. The last thing you want to do is create a potential difference of several thousand volts between your face and your feet.
In other words, feet together/one foot is only to help protect you if the lightning strikes NEAR you. It doesn’t do squat (heh) for you if you’re hit directly.
I just came up with a li’l theory:
I believe there might be another reason to stand on one foot, allthough it is pretty theoretical, and would have virtually no importance in real life.
If you stand on both your feet you provide two different routes which the electricity might take through you, thereby reducing the electical resistance of your body, compared with if you only stand on one foot, and the current only has one way to go to reach the ground. Of course, more resistance means less likeliness of being hit.
Though, as I said, this would likely have no real significance except in theory.
No, that’s not going to make any difference worth mentioning. The difference in resistance between one leg and two in parallel won’t have any practical effect at the kind of voltages and amperages we’re talking about.
The “two feet” problem is that in a nearby lightning strike, the big danger, with respect to this question, is that the charge, radiation outward, hits one foot, travels thru the body, and exits the other foot. I get that.
So, on one foot/feet tight together, what happens? The charge still goes thru the person, doesn’t it. So where does it “exit,” so to speak, and why would that theoretically be less traumatic in theory.
You mis-understand. Electrical current flows from a high potential to a lower potential, and ground (i.e. physical earth) is the lowest potential state you can find.
With feet apart, the potential gradient from the strike creates a differential. Your left foot is at 1100V (say) and your right foot is at 100V (say). If your personal internal resistance is substantially less that the internal resistance of the ground (and humans are full of water and electrolytes and make reasonable conductors under these conditions), then a large current will flow via the contact points.
With feet together, there is no current path to earth, so no current will flow through the person at all. The feet are at a really high potential, but there is nothing leading back to earth, so no current flows. There is a risk of vertical gradients, but these are minimised by crouching.
