4 ms·

How does the striking mechanism work? Doesnt the current go through the tallest object around or not nevessarily?

saiya-jin 7y ago
Well not necessarily, in many cases tree stuck (and burned to rather beautiful pile of ashes) can be an insignificant one deep in the valley, while the ones on top of the hill will keep standing. Or folks getting struck through open window in their room, while building has proper protection. We all have seen the pictures of real lightning, never straight path, rather sum of local optimums which may end up being a rather un-optimal path overall
- segfaultbuserr 7y ago
  > sum of local optimums which may end up being a rather un-optimal path overall The best summary of lightning safety I've ever read!
segfaultbuserr 7y ago
Not necessarily, lightning is an extreme electrical phenomenon. I'm no way an expert, but from what I've read... 1. Lightning doesn't have to hit the tallest object. Electricity doesn't flow into the lowest-impedance path either. It's just probability at work - lightning is more likely to hit the tallest object, and when an object gets a hit, more current flows into the lowest-impedance path, but other path will receive their shares. "Electricity finds the path of least resistance" is only a rule-of-thumb when the resistance of one path is two order-of-magnitude smaller than other path, then approximately 99% of the energy is applied to the short circuit. But when you have a lot of different path with impedance of similar order-of-magnitude, every path will receive some energy. If the object is a lightning protection system, it has incrediblly low impedance than other objects, so it will do its best to redirect all energy to ground and ensure that the probability of hitting other objections is very low, but still, if there's an unintended high impedance path within the protected system (e.g. two large metal structures are grounded separately, but not connected with a think metal bar, a voltage difference can develop between the two), then some energy won't be redirected to ground as intended and will attempt to flow through other objects with lower impedance, and it'll destroy other objects along the way. It's why we still see damages from time to time. Worse, in nature there's no such conductor designed for lightning protection, all objects are vulnerable, it's just some are a bit more vulnerable to others, like the tallest tree. 2. Lightning doesn't have to hit you directly to cause injury. Recall Electrical Safety 101, if you connect a 110V/220V "hot" wire to a grounded object, the low impedance ground will keep the voltage of such object low to ensure safety. But if it's a HV line, it's another story, the Earth itself is not a perfect conductor, the point closer to the voltage source will have less resistance, thus a voltage gradient forms, there can be a significant voltage difference on Earth between your legs.
tacon 7y ago
Lightning depends on the electric field exceeding the dielectric insulation of the air. Some random charge floating around eventually forms a current, and that is the "random" path the lightning bolt takes to discharge. Lightning rods are designed with very sharp tips, the high curvature of which leads to a higher local electric field. Thus, a lightning rod works to discharge to ground an area of air around the point and prevent a larger buildup of voltage. [0] https://physics.stackexchange.com/questions/184374/why-do-lightning-rods-have-a-sharp-point-at-the-top/184394 https://physics.stackexchange.com/questions/184374/why-do-li...
woeirua 7y ago
No, this is a common misconception. Consider the difference in electrical potential between two trees that are 35 feet tall, and one that's 20 feet tall. Is there a difference? Yes, but it's not a big one, and when you consider the overall path length from the cloud to ground you're talking about a miniscule difference. Additionally, there are other confounding variables. Taller trees are typically older, and have larger root systems. Maybe they're better grounded, relative to younger trees, and so they are better pathways. We just don't know enough yet to say for certain why lightning strikes where it does. The only thing I will say, is that if you're outside and have nowhere to go, the best place is to be in a dense forest, but not close to any particular trees. The odds of you being directly struck in a forest are incredibly small.
- DoofusOfDeath 7y ago
  > The only thing I will say, is that if you're outside and have nowhere to go, the best place is to be in a dense forest, but not close to any particular trees. Your phrasing made me smile, because I could imagine Terry Pratchet writing the same words. It would be some joke about how you needed to stand near some tree, but no particular tree. Golly I wish he were still writing.
wDcBKgt66V8WDs 7y ago
Something I learned recently was that lying on the ground might seem like a good idea, but it isn't the safest position. It is thought, though I think the science is kind of out still, that the safest position is basically squatting and holding your knees. IIRC, lying down increases the chance that a near strike will still send current over you.

Well not necessarily, in many cases tree stuck (and burned to rather beautiful pile of ashes) can be an insignificant one deep in the valley, while the ones on top of the hill will keep standing. Or folks getting struck through open window in their room, while building has proper protection. We all have seen the pictures of real lightning, never straight path, rather sum of local optimums which may end up being a rather un-optimal path overall

segfaultbuserr 7y ago
> sum of local optimums which may end up being a rather un-optimal path overall The best summary of lightning safety I've ever read!

segfaultbuserr 7y ago

Not necessarily, lightning is an extreme electrical phenomenon. I'm no way an expert, but from what I've read... 1. Lightning doesn't have to hit the tallest object. Electricity doesn't flow into the lowest-impedance path either. It's just probability at work - lightning is more likely to hit the tallest object, and when an object gets a hit, more current flows into the lowest-impedance path, but other path will receive their shares. "Electricity finds the path of least resistance" is only a rule-of-thumb when the resistance of one path is two order-of-magnitude smaller than other path, then approximately 99% of the energy is applied to the short circuit. But when you have a lot of different path with impedance of similar order-of-magnitude, every path will receive some energy. If the object is a lightning protection system, it has incrediblly low impedance than other objects, so it will do its best to redirect all energy to ground and ensure that the probability of hitting other objections is very low, but still, if there's an unintended high impedance path within the protected system (e.g. two large metal structures are grounded separately, but not connected with a think metal bar, a voltage difference can develop between the two), then some energy won't be redirected to ground as intended and will attempt to flow through other objects with lower impedance, and it'll destroy other objects along the way. It's why we still see damages from time to time. Worse, in nature there's no such conductor designed for lightning protection, all objects are vulnerable, it's just some are a bit more vulnerable to others, like the tallest tree. 2. Lightning doesn't have to hit you directly to cause injury. Recall Electrical Safety 101, if you connect a 110V/220V "hot" wire to a grounded object, the low impedance ground will keep the voltage of such object low to ensure safety. But if it's a HV line, it's another story, the Earth itself is not a perfect conductor, the point closer to the voltage source will have less resistance, thus a voltage gradient forms, there can be a significant voltage difference on Earth between your legs.

tacon 7y ago

Lightning depends on the electric field exceeding the dielectric insulation of the air. Some random charge floating around eventually forms a current, and that is the "random" path the lightning bolt takes to discharge. Lightning rods are designed with very sharp tips, the high curvature of which leads to a higher local electric field. Thus, a lightning rod works to discharge to ground an area of air around the point and prevent a larger buildup of voltage. [0] https://physics.stackexchange.com/questions/184374/why-do-lightning-rods-have-a-sharp-point-at-the-top/184394 https://physics.stackexchange.com/questions/184374/why-do-li...

woeirua 7y ago

No, this is a common misconception. Consider the difference in electrical potential between two trees that are 35 feet tall, and one that's 20 feet tall. Is there a difference? Yes, but it's not a big one, and when you consider the overall path length from the cloud to ground you're talking about a miniscule difference. Additionally, there are other confounding variables. Taller trees are typically older, and have larger root systems. Maybe they're better grounded, relative to younger trees, and so they are better pathways. We just don't know enough yet to say for certain why lightning strikes where it does. The only thing I will say, is that if you're outside and have nowhere to go, the best place is to be in a dense forest, but not close to any particular trees. The odds of you being directly struck in a forest are incredibly small.

DoofusOfDeath 7y ago
> The only thing I will say, is that if you're outside and have nowhere to go, the best place is to be in a dense forest, but not close to any particular trees. Your phrasing made me smile, because I could imagine Terry Pratchet writing the same words. It would be some joke about how you needed to stand near some tree, but no particular tree. Golly I wish he were still writing.

wDcBKgt66V8WDs 7y ago

Something I learned recently was that lying on the ground might seem like a good idea, but it isn't the safest position. It is thought, though I think the science is kind of out still, that the safest position is basically squatting and holding your knees. IIRC, lying down increases the chance that a near strike will still send current over you.