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When Lightning Strikes
ctwxman writes "For most of the United States (sorry West Coast), this is the season for lightning. It is as powerful as it is spectacular to look at. It is destructive too - by itelf or through the hail, straight line winds and tornadoes that often accompany it. As someone who forecasts the weather, I'm often asked about lightning. As you might imagine, there's plenty to see about lightning on the Internet. The conditions necessary and a little bit of the physics behind lightning are explained by Jeff Haby, a meteorologist (one of my professors actually) at Mississippi State University. Once forecasters get a handle on what's going on, they put the word out through the Storm Prediction Center. Regular outlooks are issued by SPC for severe storms. Once those storms rear their ugly heads, they're followed with mesoscale discussions looking at the active areas. The Storm Prediction Center is also the place where Severe Thunderstorm and Tornado Watches are issued and storm related damage reports are compiled. Lots of hobbyists like to track lightning strikes on their own, and there's equipment available to do just that. Getting hit by lightning is never fun, though not always fatal. National Geographic chronicled an amazing story of a lightning strike, and rescue, on Grand Teton."
Sorry West Coast ....
Umm.. the constant threat of earthquakes is nothing to sneeze at... while not as loud as thunder/lightning it's sure can be a wild ride.
http://quake.usgs.gov/recenteqs/latest.htm
he was in his pool ans could hear thunder in the distance so he throught he should probably get out, but as the cloud got closer the surface of the pool started to "boil". The huge negative chage in the cloud induced an equal positive charge in the ground underneath it. As this positive charge was attracted to the cloud it made ions in the water making it boil. After pondering that for a minute he jumped ou tof the pool so as not to be killed.
Dear aunt, let's set so double the killer delete select all
I know Im going to get modded down for this; but Ive lived in Wa, Tx, Ak and Az; and out of all of them, its (ironically) been in Az where Ive seen lightening the most intensely (longer duration, and more clearly visible) and also the most closely (within blocks of where I live).
Absolutely breathtaking.
I've never been directly struck by lightning, but I have been "zapped" i guess you can say, by some sort of mild electric shock when a big bolt hit right near my apartment complex.
I ran upstairs to the 3rd floor, to shut a window because it had been raining.. I go to close the window, i'm standing on wet carpet (the whole room is practically soaked) and suddenly BLAM. Big lightning strike, and I got shocked. It almost felt like my whole body was doing a tongue test on those square 9v batteries. Probably the closest i've ever come to being struck.
Has this happened to anyone else? I had previously believed that one could only get struck or zapped by lightning outside of a house.
For even more fun, don't forget about the Jesus actor in the Passion of Christ being struck by lightning during the filming. The assistant director was hit twice. Probably a pissed off God -- mad that it's supposed to be realistic, what with the Aramaic and all, but Mel Gibson used a white Jesus.
And then there's Roy Sullivan. A quick google turned this up:
Roy Cleveland Sullivan was a Forest Ranger in Virginia who had an incredible attraction to lightning... or rather it had an attraction to him. Over his 36-year career as a ranger, Sullivan was struck by lightning seven times - and survived each jolt, but not unscathed. When struck for the first time in 1942, he suffered the loss of a nail on his big toe. Twenty-seven years passed before he was struck again, this time by a bolt that singed his eyebrows off. The next year, in 1970, another strike burned Sullivan's left shoulder. Now it looked as though lightning had it out for poor Roy, and people were starting to call him The Human Lightning Rod. He didn't disappoint them. Lightning zapped him again in 1972, setting his hair on fire and convincing him to keep a container of water in his car, just in case. The water came in handy in 1973 when, seemly just to taunt Sullivan, a low-hanging cloud shot a bolt of lightning at his head, blasting him out of his car, setting his hair on fire and knocking off a shoe. The sixth strike in 1976 injured his ankle, and the seventh strike in 1977, got him when he was fishing, and put him in the hospital for treatment of chest and stomach burns. Lightning may not have been able to kill Roy Sullivan, but perhaps the threat of it did. He took his own life in 1983. Two of his lightning-singed ranger hats are on display at Guinness World Exhibit Halls.
riding round the world on an old motorcycle
I think this will be the season for antennae and wireless shops around the US. With the growing WAN's around the place, and the endless similarity between a lightning rod and those antennae... Ouch!
Fun to watch but expensive to reproduce...
Beta Sucks
Have a look at this, for example.
My wife's best friend was killed by lightning in Houston in 2001. A storm had passed though about a half hour before and it appeard to be clearing. She went into the front yard to do some weeding in a flower bed beside the driveway. Her house was in the middle of a bunch of very large pines. They probably had 2 dozen 75-100' pine trees throughout the yard and the entire lot was under the canopy. Not to mention that there were 2 aluminum light poles within 25 yards of where she was struck. Examining the damage afterwards, a tree was struck. The lightning travelled along the tree for about 15 feet and then must have travelled through the air, through her body and into the rebar in the driveway (or reverse that since lightning supposedly travels up). A neighbor began cpr within 2 minutes and they had her to a hospital within 15-20 minutes. They got her heart working again eventually, but never any brain activity. I kinda like to think that she died immediatly. From what I was told, there wasn't any visible damage to her body except for some blood from her nose and mouth (that was third hand since the neighbor wouldn't talk about it).
I spent a lot of time in the Rockies during Summers of my youth. We were taught that if the hair stood up on any part of our body, ditch the backpack and dive flat. I saw a guy who had three quarters and a pocketknife end up with an entry point of some metal slag who was caught by surprise.
Also, there are different types of lightning & static activity - Tesla seemed to be the master during his lifetime. One of the most baffling types of static|lightning activity is ball lighting. There have been stories for a long, long time beyond FOAF|UL describing a small globe of what appears to be lightning in an orb, having appeared out of nowhere, moving about without a pattern, then disappearing as mysteriously. IIRC, most of the reports involve aircraft. Tesla demonstrated great prowess in creating them, controlling them, and destroying them, to the bewilderment of all. And for all who thought he was a crackpot while he was alive (including the gov't), why did they pack up all of his belongings when he died and send them off to parts unknown?
I am a weather spotter for the national weather service and I have seen some interesting storms here in VA... We once had a storm so intense that the sky was dark enough around 2:00pm that you could see stars in the breaks of the clouds and the moon was "shining." That was freaky - apparently, that storm spawned a "small" tornado that threw individual blades of grass through a telephone pole. In 1985, the southern part of the state, where I am originally from, experienced the "Flood of 85." The Roanoke river crested at a record 23 feet... tons of damage was done, but some amazing stories, like that of an aging Labrador retriever in Eagle Rock that pulled its master to safety out of the rolling waters of Craig Creek, came out of it... Here is a photo of the Roanoke stadium.
A guy I know put an antenna up in a pine tree, about 70 feet, without a ground wire. Needless to say it got nailed, about 2am while he slept. Detonated the antenna, peeling it into 2ft long, thin strips of fiberglass. Boiled his coax, all the way into his house. Electrofried his radio, and set its power cord on fire. (under his bed, where he was sleeping, setting the carpet on fire) Blew the outlet off the wall. Got into the breaker box and destroyed several breakers, two microwaves, and three color TVs. Finally found ground via the phone entrance box on the outside of the house, which was blown off the house. This was the SECOND time he had been hit, the previous time was the same exact scenario, just not as damaging.
A guy down the block got his ham radio antenna hit, blowing the base of the antenna to pieces. (severing the ground connection in the process, unfortunately) The lightning then took out his coax like det cord, which was laid down under one layer of shingles. This shot the shingles that were laid over the coax right off the house. It then took out his radio, followed the power cord into the electrical system in his house, took out all the appliances in his kitchen, and then went underground to his garage and took out three marine radios that were on charge at the time.
A friend and former co-worker had an employee of his arrive late to work. When asked of the excuse, he said he got his truck struck by lightning on the way in. And boy did he. They never found any of the whip antenna. The base of it, solid brass, was melted like ice cream. Blew out the back sliding windows where the coax came into the cab. Blew the radio to pieces. Finally found ground via front left quarterpanel, which was permanently bowed inward from the sudden heating.
I worked on someone's computer recently, they had pictures on their desktop of a relative's car that was struck while going down the highway. It hit the rear mounted stereo antenna, arced into the body of the car, (creating a 1/2" hole in the metal near the antenna mount) and found ground via ALL FOUR TIRES, arcing across the wheel wells and apparently through the steel belts, flattening all four tires in the process. It also blew out the rear window from the concussion.
My car was struck by lightning while on the road too. Took out the headlights and the windshield wipers, which then started working normally a few hours later. (probably tripped the breakers that those items usually are on instead of fuses)
I have a large ham radio antenna at my house as well, which has been struck at least three times so far, you can count the char marks on it. Thanks goes to a 1/4" solid aluminum ground wire and a 10ft copper water pipe for a ground rod, the lightning has never even scratched my radio, which remains plugged in and cabled up 24/7.
Lastly, if you're ever on a beach and run into a patch of what appears like a cross between pavement and sand, that's where lightning has struck the beach and melted the sand into glass. Really weird effect...
I work for the Department of Redundancy Department.
It's a nice thought, harnessing the power of lightning. And it's true that there's a really high power output. However, the duration is so short that the total energy, in terms of kilowatt-hours, is typically on the order of US$0.20 - US$0.30 per lightning flash.
When we in the University of Florida lightning research group trigger a lightning flash, we use a $500 rocket to get that US$0.30 worth of electricity. This alone makes the whole process very cost-ineffective. Add to this the fact that there is not a good way to store that much energy that quickly, and you quickly realize that it's simply not practical to try to store lightning energy.
I'll be glad to share more information, if anyone's interested.
Ce n'est pas un vrai mouvement de robot!
There was a flash very big boom, during which a piece of electrical equipment up the street turned into sparks. A moment later, the sky lit up again, this time not white, but blue.
My office is on the forth floor in a not very big town, so I have pretty good view of a lot of it, and it was lit up as bright as the brightest of sunny days. But blue.
I believe I saw a flashover, which occurs when lightning hits something electrical, and the electricty within, which had previously been happy doing its thing, jumps out and follows the lightning bolt's path. This can continue for several seconds after the lightning has stopped.
My girlfriend was there to see this too--in fact, she dropped to her knees and said "that's the scariest thing I've ever seen." And I agree. Lightning is fascinating stuff, and terrifying.
If you ever get a chance to travel around in the southwest, try to stay at the Lightning Field in New Mexico. It is a rustic stay at the cabins there but it is worth staying there overnight. Even without the lightning strikeing the sculpture it is an awesome site. The field is most active during the summer months past July. http://www.lightningfield.org/ Support the arts!
Humans, on the other hand, don't have as much of a problem, because their feet are so close together.
My own experience with lightning, for the lack of a better word, was simply awesome and I'm glad it wasn't a closer hit. A thunderstorm developed over the neighbouring fields of my parent's farm and slowly made it's way over our fields. It was an extremely hot and humid day, the sudden down pour settled the dust quickly while the temperature dropped several degrees in a few seconds. I watched a lightning bolt strike the ground in the middle of a flat empty field leaving the ground smoking even though it was raining cats & dogs.
I happened to be standing at the patio door: bare foot on a forced-air furnace register (vent) which was effectively well-grounded. The next lightning bolt struck a nearby tree or the house. It didn't really matter where it struck. I could literally feel the charge race through my body and make my hair stand on end. The flash and boom were simultaneous.
A few minutes later we were sitting at the kitchen table. Another close-by strike caused a 6-inch long blue arc that leapt from the electric stove's fuse panel through a stainless pot and grounded out through the stove's element. It also blew out all the lights on that side of the house.
That was by far the scariest storm I have ever experienced.
by pure coincidence I opened my browser to /. while waiting for the voltages to come back up and I see this story up at the top.
We typically see a peak current of about 10 - 30 kA per stroke, with an average of 2 or 3 subsequent strokes per flash. That's the successful triggers, of course. We only get current at ALL about 50% of the time, and about 25% of the time we get actual return strokes.
We often strike a section of de-energized power line, with a (nominal) impedance of 400 ohms. That translates into peak voltage of 10 megavolts as a first approximation, and about 250 gigawatts. But, since the peak duration is no more than a couple of microseconds, that's about 500 kilowatt-seconds, and 138 watt-hours - less than a single kilowatt-hour.
Er - what do you do, to consider 25 kA "not much current"? Just wondering...
Ce n'est pas un vrai mouvement de robot!
Lightening happens around here (west coast) and the coax goes out the window the radios get disconnected from the AC. 10 foot ground rods last about 3 months in this soil. My tower has 4 #10 copper leads anout 10 inches long going to "ground." I am knocking on wood I haven't lost anything to EMF but hams just 2 blocks away have lost rigs and computers to Lightening EMF and leaving stuff connected. Oh and I don't leave the tower cranked up when I am not home or during storms. I hope the path of least ressistance is through the palm tree in my Neighbors yard or the Jupiner in the other ones both which are taller than any antenna usually have up.
If you don't like what I write don't be a CS and mod it down. Refute it.
Yea I can't spell. So what is your point?
So then, what happens to your router?
You may feel safe, but any strong "local" (100m radius) strike will likely induce enough current in the front end of your wi-fi card to fry it regardless.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
About two weeks ago, during an after-school rehearsal of Macbeth, we heard a sharp clap of thunder as the three witches were reciting "Double, double toil and trouble; Fire burn, and caldron bubble....". We were startled at first yet were quickly amused at its timing. One of the actors emerged from the dressing room quite pale and said he saw a flash of light streak along one of the walls.
After the rehearsal, I returned to the computer lab, sat down at my PC, and noticed that it was powered down... and it wouldn't power up. I wandered into our LAN/Server/Broom/Tool/Ex-Bathroom closet and discovered that 2 servers, 4 PCs, our SDSL router, our 24-port Switch, and the Ethernet port on the motherboard of 10 new PCs were all dead. The PCI NIC in my PC had a crater in it. Our PBX was toast and the 25 and 50-pair phone cables between buildings were severely damaged as well..
If you'd like to see a short Flash-enabled gallery of the destruction, go here As usual, click on a thumbnail to see a larger image.
A company that is no longer in business installed our punch-down blocks, and they grounded the blocks to a faucet attached to a copper pipe. The person who did the plumbing on the building said that the copper pipe does not travel far before it continues its run as a PVC pipe. The cable and punch-down block installer did not use a true power ground with a 6-ft spike in the ground. We did have lightning arresters on the blocks, but I found the one connected to our SDSL line charred on the floor. It got blown off the wall (one million volts, 200,000 Amps coming through!) The surge traveled over our data network, not through the AC power supplies.
I've also been looking at web sites that indicate that there's no conclusive proof that lighting rods are effective deterrents even though they're recommended in many building codes.
Having fun in Austin,
A Chief Technical Agonizer
p.s. We discovered today that the light board in our auditorium also got nailed. It's like "Close Encounters" in there without the tones, but then again, we haven't fully tested the sound board yet. Who knows what we'll find tomorrow !!!
The part of lightening study that fasinates me is the discovery of sprites,a part of a lightening strike that moves spaceward.
Here is a pic of a sprite.
This is linked to in a longish article. See under Recent Developments.
The use of a large, really large fixed object such as a really tall tower or a skyhook would allow for the capture of a significantly increased amount of lightning, true. That is a very good point. That doesn't solve the storage problem, though.
Our rockets themselves aren't that expensive, truthfully. And we can usually reuse the rocket proper, we just load a new motor in it. Those are cheap. What's expensive is the spool of wire attached to the rocket. You'd think that getting 700 m of 32 ga wire wrapped on a spool would be cheap, but to get a spool wrapped with 32 ga Kevlar-reinforced wire which will spool off cleanly every time is, in fact, a non-trivial task. That's where most of the $500 figure comes from. That DOESN'T include the costs of site maintenance, personnel, range safety, etc.
The typical successful trigger occurs at something between 300 m and 700 m here in Florida. It may be different elsewhere, where the clouds are higher.
Lightning flashes HAVE been triggered with large lasers. But we don't have one. We could probably get one, if we could find someone to fund the purchase, but then the amortized cost per flash would probably (yeah, I'm just guessing) exceed the cost of the rockets we use now.
Most of my class notes are pretty well encapsulated in the book my profs wrote, Lightning: Physics and Effects by Rakov and Uman. I imagine Amazon has it, but it's real spendy - I don't even own a copy. However, it's pretty much a definitive and comprehensive treatment of the subject. The bibliography alone is worth the price.
Ce n'est pas un vrai mouvement de robot!
Yes, the E field across the ground is bad - I knew a caver who was deep inside a cave, and was shocked by the cave wall when a strike hit the ground above.
That's also why you should NOT lie down on the ground to avoid a strike - instead, you should "become a basketball with feet" - curl up into a ball and balance on the balls of your feet, with your feet as close together as possible (if your balance isn't good enough, then put your feet flat). That way, if a strike hits close to your, the potential across the parts of you in contact with the ground will be at a minimum.
That's also why equipment connected to radio towers should, ideally, be in a Faraday cage (a closed conductive container) - an E field will not penetrate a (perfect) Faraday cage, and will remain on the outside. (Of course, that "perfect" bit is the hard bit, so some field will leak inside, but nowhere near as much as without.)
And as a previous poster pointed out, it is the fact that most cars are pretty good Faraday cages that protects you from lightning in a car, not the rubber tires - the lightning jumped an air gap of several hundred metere, what makes you think a few centimeters of rubber are going to stop it?
Of course, if you are in a modern plastic car....
Even worse, imagine taking a strike in a Prius or other electric/hybrid electric car with a significant amount of battery....
www.eFax.com are spammers
Another amazing video is of a plane getting hit by lightning at a Japanese airport--check it here.
Bottom line: planes can be just like a big hydrometeor from lightning's perspective.