please explain the logic of a lightning strike - PeachParts Mercedes-Benz Forum

JB3 · #1 06-28-2011, 04:57 PM

During that big storm the other week, the tenant of a house I am renting out calls me and tells me that lightning struck right outside the house. Check out these pics.
The lightning blew a big hole in a rock wall, which is 4 feet from the side of the house, 2.5 stories high with a peaked attic. It blew dirt and mud up onto the roof of the house and there are mud splatters on the second story windows and whole side of the house. I found mud splatters 30-40 feet away. Im amazed that it avoided both the lightning rod on the roof, and the A/C unit 3 feet away.

Why would the shortest path be through this low stone wall? it is right next to the house, and also on the bottom of a hill, apart from the walk, its actually the lowest surface in the area, probably for over 50 feet.

Im pretty happy that all I have to do is get another bush for right there, and repair the wall vs fix a huge hole in the roof, replace the A/C unit, or be dealing with fire damage, but Im curious how with all the other far more conductive things in the immediate area, the stone wall is whats destroyed

MTI · #2 06-28-2011, 05:05 PM

gotta love the randomness of nature sometimes. Makes fools of humans, particularly engineers, all the time.

leathermang · #3 06-28-2011, 05:07 PM

One of the advantages of a proper lighting rod system....is that is bleeds off the build up of electrical differences between the air and the ground... where it can not bleed off it comes to neutral the hard way..
But I must say that is an ugly stone wall and I understand why the lightning was trying to dismantle it...

www.arpapress.com/Volumes/Vol7Issue3/IJRRAS_7_3_08.pdf

Check out this one... the place in AFrica where lightning hits the most...
much has to do with the composition of the soil... clay being the more dangerous type ..

http://www.wonderquest.com/where-lightning-hits.htm

JB3 · #4 06-28-2011, 05:21 PM

Quote:

Originally Posted by leathermang

But I must say that is an ugly stone wall and I understand why the lightning was trying to dismantle it...

lol, thanks for the links, very interesting.

its a mostly dry field stone wall, one of several billion in the new england area built by farmers for the last 300 years. The section that was hit had recently been put back together with concrete in a squarer shape. Sorry we are not up the the stone wall standards of texas.

There are 9 of these old walls here and there on this 2 acre rental property. If you wanted to eradicate your property of field stones, you would die of old age before you got them all. These walls add to the local feel of the area. Most of them have been around for two hundred plus years.

865sp300e · #5 06-28-2011, 05:46 PM

The tallest objects in a storm don't always get struck by lightning. It's true that taller objects are closer to the clouds, but lightning can strike the ground at a close distance to a tall object. Taller objects may have a higher possibility of a strike, but where lightning is concerned, the strike path is not predictable.

There are usually many separate paths of ionized air stemming from a cloud. These paths are typically referred to as step leaders. As the step leaders approach the earth, objects on the surface begin responding to the strong electric field. The objects reach out to the cloud by "growing" positive streamers.

Next to occur is the actual meeting of a step leader and a streamer. The streamer that the step leader reaches is not necessarily the closest streamer to the cloud. It's very common for lightning to strike the ground even though there is a tree or a light pole or any other tall object in the vicinity. The fact that the step leader does not take the path of a straight line allows for this to occur.

After the step leader and the streamer meet, the ionized air (plasma) has completed its journey to the earth, leaving a conductive path from the cloud to the earth. With this path complete, current flows between the earth and the cloud. This discharge of current is nature's way of trying to neutralize the charge separation. The flash we see when this discharge occurs is not the strike -- it is the local effects of the strike.

When a leader and a streamer meet and the current flows (the strike), the air around the strike becomes extremely hot. So hot that it actually explodes because the heat causes the air to expand so rapidly. The explosion is soon followed by what we all know as thunder.

tbomachines · #6 06-28-2011, 06:02 PM

^ Great summary!

http://www.youtube.com/watch?v=2XwFF5idD_0

lightning has always fascinated me, every storm I try to get out and photograph some even though my camera is not very good. We had a strike last year, my brother and father were sitting the storm out in their car after returning from the store when it struck a tree about 30ft away. The current went through the tree and continued on to our house, evidenced by the explosion of dirt and fire (soaking wet grass burning, neat!) 20 feet to the foundation of the house. It created a ditch of burned dirt and caked the house in mud.

MTI · #7 06-28-2011, 06:19 PM

If only we can get it to the flux capacitor!

Chas H · #8 06-28-2011, 06:30 PM

Lightning struck our garage to which the family dog was chained. The lightning followed the chain out to the dog and melted the choke collar off its neck. The chain links were fused to gether in pieces about 4-5 ft long.
The dog survived and lived for many years after, but was not ever quite the same as before.

MTI · #9 06-28-2011, 06:45 PM

awww, poor Sparky!

leathermang · #10 06-28-2011, 06:55 PM

Quote:

Originally Posted by Chas H

.., but was not ever quite the same as before.

He was not the same because he had received therapy...

http://en.wikipedia.org/wiki/Electroconvulsive_therapy

DeliveryValve · #11 06-28-2011, 07:10 PM

Holly cow, that's crazy!

Here some lightning facts..
http://www.lightningsafety.com/nlsi_pls/probability.html

Quote:

Lightning Strike Probabilities

1. ASSUME -

4 CG flashes/km2/yr/average

House is 10 X 20 m2 = 200 m2

Direct strike to house when lightning hits within 10 m

Predicted strike (1200 X4)/1 000 000 =

4.8 X 10 -3 or once ea. 200 years

Therefore - 1 out of 200 house will be struck per year.

2. ASSUME -

USA population = 280,000,000

1000 lightning victims/year/average

Odds = 1 : 280,000 of being struck by lightning

.

Chas H · #12 06-28-2011, 08:17 PM

Quote:

Originally Posted by leathermang

He was not the same because he had received therapy...

http://en.wikipedia.org/wiki/Electroconvulsive_therapy

McMurphy didn't change, much.

Skippy · #13 06-28-2011, 11:07 PM

I had a boss who had been struck by lightning once. We had an outdoor job, and the first sign of lightning meant we were done for the day. I didn't mind.

leathermang · #14 06-28-2011, 11:57 PM

Quote:

Originally Posted by Chas H

McMurphy didn't change, much.

Most dogs are very well adjusted... so he did not need much changing .... just a few electrons realigned in his telencephalon.

http://www.ehow.com/about_6765749_anatomy-dog-brain.html

The Swede · #15 06-29-2011, 12:01 AM

Jebbus doesn't like stone walls.