Looking around my big-city neighborhood, none of the houses have visible lightning rods. Why not?
Well, the Master himself has a number of articles on the subject, and there’s some evidence that they don’t work at all.
It’s a little bit of a hairy topic. First of, Franklin’s theory of how they worked was wrong. Others have improved on the theory, and method, for example Tesla. There are other methods to protect a building, using terrain, and even pine trees apparently.
If they’re not installed properly, they do more harm than good. And that’s a lot of power – the Mythbusters have pointed out, we can’t generate, store, and release synthetic lightning with the same amps that the sky can generate, so any testing is hard to do.
Then again, people have been putting spikes on top of buildings since forever, and those buildings (anecdotally) survive better.
My wag – we have fire departments and fire insurance nowadays. Lightning rods were more important in olden times.
Houses are grounded. Every house has a copper stake driven into the ground near the electric meter. That should transfer some of the electrical power, from a strike, into the ground.
That’s still not the same as having a lighting rod on the roof. It seems those are only found on taller buildings.
I was surprised to discover that the data center where I work has a lightning rod. The facility engineer took us on a tour of the roof and made a point of showing it to us. It makes sense, considering the nature of our business, but it wasn’t something I expected to see.
Most houses have a metal sewer vent that acts as ground. This is what TV antennas were grounded to. If not for this ground, the static electricity of a nearby lightening bolt would be picked up and transmitted to the TV. The effect would be that of a cheap sci-fi movie with sparks shooting off the back of the set. Experienced that at my parent’s house when the grounding strap corroded off.
Not many houses built in the last 40 years - they’re pretty much all PVC.
That happened to us when I was young. A lightning bolt either hit the house directly or a nearby power line. It blew out almost all of the appliances in the house but we were watching TV at the time and it basically just exploded sending sparks everywhere and almost caught on fire itself. Our nanny was watching us at the time just sat on the couch and did nothing. She said “When lightning hits, I sits”. It was some of the best advice I had heard in a while.
I woke up to the sounds of a massive thunderstorm this summer that ended in a circa 1814 church right down the street being partially destroyed. I wish something like a lighting rod could have saved it the steeple. I hate lightning. It is pure evil.
http://www.boston.com/news/local/breaking_news/2009/07/lightning_strik_1.html
If the houses are in a big city neighborhood odds are they don’t need to worry about having their own lightning rods. They have those big city skyscrapers nearby to soak up the lightning blows.
I occasionally deal with houses that have been hit by lightning. Some of the more expensive hilltop homes that get hit frequently have installed lightning rod type grounding. It does help with some strikes but even on those homes occasionally I’m there after a serious strike that still resulted in something exploding(in my case the usually the water pump)
We have a series of lightning rods on the barn; the farm is at the top of a hill and is the highest ground in about a mile’s radius. I’m actually not sure if there’s a lightning rod on the house, but they are definitely in use in rural areas of Ontario.
We have a couple on our 105 year old farmhouse.
wood or any part of your house looks equally good as the earth to a lightning bolt that has just traveled many miles through air which is not very conductive.
They certainly do still use them – my brother-in-law’s business is largely installing lightning rods.
Older theories about lightning rods are certainly wrong, but I’m surprised at suggestions that the rods don’t work. It’s not as if they haven’t been tested a lot by places like General Electric. They’ve even built lightning generators to produce lightning for such tests. Plots of lightning strikes around rod-protected structures using these devices show that properly-installed rods do, indeed, prevent the lightning from striking nearby structures or the ground – by taking the lightning hit themselves, rather than by dissipating electrical charge. (See Peter Viemeister’s The Lightning Book for plots of such strikes http://www.amazon.com/exec/obidos/ASIN/0262720043/ref=nosim/weisstein-20) The Wikipedia page tallks about the difficulty of locating lightning strikes in the Real World (Lightning rod - Wikipedia ), but these laboratory scaled-down tests do indeed show protection.
As for the thing about sharpened points, let me point out once again one of my favorite physics papers, The Lightning Rod Fallacy by Richard Price and Ronald Crowley in American Journal of Physics Vol. 53 (9) 843-848, September 1985. The usual statements about the electric field being strongest where the radius of curvature is tightest on a conductor and shown to be incorrect and misleading, and they give copious counter-examples to the basic case and to attempts to refine the statement. Lots of EM theory fun for all.
Lots of church steeples have them. Seems to be a lack of faith.
It’s really bad advertising when God smites your church with lightning.