Wednesday, June 30, 2010

Our house was hit by lightning

Believe it or not, our house was struck by lightning! It happened a few days ago, as a cold front swept over, bringing with it some intense but short-lived thunderstorms.

I was working on my computer when I heard a loud POP sound of a spark, behind me, in the utility closet. At the same time my computer went blank, and there was insanely loud thunder clap. My poor son was on the toilet at the time and told me he was so startled that he jumped high in the air and almost fell in! Fortunately, none of us were hurt.

The strike destroyed our central 16-port gigabit ethernet switch, 3 out of 4 LAN ports on my FIOS NAT box, a couple power supplies and one netcam. It also fried the device I use to read the electrical (charging, inverting) data from the solar panels in my back yard, but the solar panels themselves, including the thick copper ground wires designed to "guide" lightning into the ground and away from the house, were all fine, as well as the charger, inverter and batteries. My 1-Wire network, which I use to measure various indoor & outdoor temperatures, is also still dead. My wife's computer immediately shut down and rebooted, several times (spooky), but apparently unharmed. My computer seemed to lose both ethernet ports, but then after much rebooting and testing plug-in ethernet cards, they came back to life.

A large tree branch in our neighbor's yard fell down; the neighbors across the street called the fire department; yet another neighbor saw bright sparks in his basement and also lost a bunch of electronics.

Almost certainly this was not a direct strike for us; otherwise things would have been vaporized instead of simply dead. Instead, the sudden immense electro-magnetic field created at the direct strike radiates outward, creating the local equivalent of an EMP bomb. This EMF then induces high voltage and current in any wires it crosses; the closer you are to the direct strike, and the longer your wires are, the more damaing the induced voltage and current is. In my case, apparently, the extensive network of ethernet wires in my house cause most of the damage. This is a good reason to use WiFi!

I will now buy myself something to try to prevent this from happening again.

Lightning is crazy stuff. The process the lightning goes through in seeking the path through which it will dump insane amounts of current is fascinating. National Geographic has a great facts page; for example, talking on your land-line telephone is the leading cause of lightning injuries inside the home. I suspect we may have been hit by positive lightning, because we seemed to be hit, out of the blue, well before the storm itself seemed to arrive.

Lightning strikes are apparently rather common; in just my immediate family this has now happened twice to me, and once each to my brother, father and grandparents!

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