Wow. It is not only wierd that the lightning struck that particular rock rather than a tree or something, but also amazing that it actually burned that hole where it struck.
I have a healthy respect for lightning. We stay inside when there is a thunderstorm. A couple of years ago lightning struck the telephone box on the outside of the house. Having our landline through the cable company everything is interconnected with coaxial cable. It blew the plastic box off the house. The box is where the phone company line used to hook up. It had been transformed somehow to allow the signal to go from the cable company coax to the inside phone wiring. It blew the plastic as far as 20 feet from the house, and somehow fed back through the cable and fried our tv. We have surge protectors on all of our electronics, but the cable guy said that the fact that it traveled via the coaxial cable rather than creating a power surge in our electrical system, the surge protector didn't protect the tv. He said it was a miracle that the coaxial cable carried it without melting and starting a fire. They replaced all of the interior coaxial cable. I don't know why it didn't fry my computer. I am lucky I guess.
Many years ago when my oldest son was in high school, a couple of his classmates were electrocuted by a lightning strike while sleeping in a tent. I don't remember the specific details but I remember how he and his VVS classmates were devastated by the tragedy.
The coax connects to my router which attaches to the computer. It didn't damage the router either. I don't really understand the circuitry. We have since changed providers and everything comes over a fiber optics line rather than copper coax to the house and into some sort of device they installed on the outside. From there it connects to the phones, internet connection, and cable tv already in the house.
Best protection means that coax connects low impedance (ie less than 10 feet) to earth ground BEFORE entering a building. No protector does protection. Due to a missing or compromised earth ground connection, one might have been blown off the side of a building.
Since all coax and telephone wires must make a low impedance (ie hardwire has no sharp bends) connection to earth (as required by code), then surges rarely enter on that path. Wires that are not required to have effective protection (ie AC electric) are most often an incoming path. Since this is electricity, an outgoing path also must exists at the exact same time.
Incoming on AC mains. Destructively through electronics (TV, computer and router, etc). Then outgoing to earth ground via that properly (or poorly) earthed cable. Damage is often on an outgoing path.
Many use wild speculation to assume the outgoing path was an incoming path. Then blame a TV cable, telephone, satellite dish, etc for damage. Why would that coax cable not suffer damage? Because a surge was incoming on AC mains and outgoing via interior wires.
If any one wire enters without a connection to that same earth ground, then all protection is compromised. It explains why some have suffered damage to their optical network terminator (ONT) and other network devices. Fiber does not guarantee protection. Only correctly installed connections to properly earthed electrodes does.
Why did lightning strike that rock? It is always about how a cloud (ie three miles up) connects to earth borne charges (maybe four miles distant). Underlying geology says so much about why a tree or a nearby mountain is not struck. Apparently that rock made a best connection to distant earthborne charges. That electrical discharge is always about both an incoming and outgoing path. Apparently it found that rock as a better outgoing connection to distant charges. So it need not find a better (destructive) connection via household appliances.
Wow. Thanks for the extremely informative and educational explanation Westom. Are you and electrician, an electrical engineer, or are you just well versed on all things electrical? I have become reasonably adept at most home related skills, including carpentry and plumbing, but electrical is something that I leave to a professional other than replacing a switch or a wall plug where I have the old item in front of me and can either label the wires as I disconnect them or am able to move one wire at a time.
Are you and electrician, an electrical engineer, or are you just well versed on all things electrical?
As an engineer, I have yet to build anything that worked the first time. No matter how careful and how many times I check, still, it never works the first time. Marking everything reduces the number of complications. But there is always something new to learn.
We traced surges to learn / confirm why damage happens. In every case, it is defined by what Ben Franklin demonstrated over 250 years ago. We are all taught this stuff. And then so many ignore science to do only what hearsay, advertising, wild speculation, and subjective reasoning recommend.
Most of this stuff was learned by having damage. Then going back to investigate / discover what human mistake made damage happen. Engineering knowledge helps. But far more is learned by that strategy.
Protection from direct lightning strikes is routine. A protector is only as effective as its earth ground. Damage occurs when a human mistake has compromised well proven science.
I guess science is not one of my strong points. I do recall now that when I was working for the 485th EIG at Griffiss, a group whose mission was to install and maintain communications towers and radar antenna sites all around the US, Greenland, the Azores, and all over Europe, that they used some heavy, long and fairly large diameter copper rod coupled with copper sheeting or matting buried in the ground to provide protection from lightning for large antennas and towers.
I am one of those who fell prey to the myths, speculation, and hearsay, with little attention ever paid to the scientific facts. Thanks for expanding my knowledge. One of the wonderful advantages of being retired is that with the internet and social media allows us to delve into something new and learn whenever our curiosity is aroused.
The 485th presence in Thule Greenland was almost constant. They worked with the Danish to support the mission there. I know that they performed much of their work on the glacier so I am relatively certain that they encountered the challenges you describe not only with frozen earth, but also with the ice pack.
My familiarity with the grounding materials is based not so much in seeing very much of the material. My normal field of expertise was transportation. I did spend period of time during my career working at our headquarters at Tinker AFB in Oklahoma as an "installation resources manager." One of the resonsibilities of the position was to coordinate with other logisitics functions to insure that materials supplied by vendors were delivered to the jobsite and were available when the installation team arrived on site to perform the installation. The responsibility included support for not only units not only in the US, but also in Europe and South Korea, as well as supporting the missions of Air National Guard units throughout the US. In short, I was pretty familiar with the materials used in grounding, but seldom saw any of it.
Last Edit: May 15, 2019 10:21:28 GMT -5 by Clipper
LOL. My field was transportation management, although over the years I have put a lot of miles on charter buses and tractor trailers as a part time driver, and after Griffiss closed I spent the last 4 yrs that I worked before retirement as an over the road truck driver. I held a class A commercial driver's license for over 35 yrs. My only experience that could be counted as "ice road trucking" would be a winter spent hauling paper in Minnesota. We used to travel from International Falls and Fort Francis Ontario to Dryden Ontario over a 125 mile long former logging road. There was not a house or building for the entire 125 miles. We often would travel the entire 125 miles and only pass one or two of our own company trucks going the other way. For safety reasons we traveled in pairs