Do trains get hit by lighting if so what happens

[Anonymous]

Perhaps some of you folks have walked along the tracks, and noticed regularly spaced pits in the rail often mistaken for " Burn-outs" from a slipping locomotive (s).
Chances are, those are the result of a lightning strike on the train. A slipping locomotive will leave smooth grooves on the rail head. When you see regularly spaced "divots" with pitting, and irregularity, THAT is the result of lightning.
Anybody familiar with "arc-welding", knows that as little as 100 amps will melt steel. I am not an expert, but I'm sure that a lightning strike packs a hell of a lot more than that.

[Anonymous]

Perhaps some of you folks have walked along the tracks, and noticed regularly spaced pits in the rail often mistaken for " Burn-outs" from a slipping locomotive (s).
Chances are, those are the result of a lightning strike on the train. A slipping locomotive will leave smooth grooves on the rail head. When you see regularly spaced "divots" with pitting, and irregularity, THAT is the result of lightning.
Anybody familiar with "arc-welding", knows that as little as 100 amps will melt steel. I am not an expert, but I'm sure that a lightning strike packs a hell of a lot more than that.

[Mookie]

QUOTE: Originally posted by dharmon

Well, for those of you that have served, remember, the two most useless ranks, O-1 and O-4 (Ensign/2LT and Lieutenant Commander/Major) are gold and the rest of the ranks are in silver....so there must be some merit to that argument

I learned the AF ranks many years ago, so this really cracked me up!

La Mook [:D]

[Mookie]

QUOTE: Originally posted by dharmon

Well, for those of you that have served, remember, the two most useless ranks, O-1 and O-4 (Ensign/2LT and Lieutenant Commander/Major) are gold and the rest of the ranks are in silver....so there must be some merit to that argument

I learned the AF ranks many years ago, so this really cracked me up!

La Mook [:D]

[dharmon]

Well, for those of you that have served, remember, the two most useless ranks, O-1 and O-4 (Ensign/2LT and Lieutenant Commander/Major) are gold and the rest of the ranks are in silver....so there must be some merit to that argument

[dharmon]

Well, for those of you that have served, remember, the two most useless ranks, O-1 and O-4 (Ensign/2LT and Lieutenant Commander/Major) are gold and the rest of the ranks are in silver....so there must be some merit to that argument

[adrianspeeder]

I was taught that pure silver was a better conductor than gold, but it tarnishes so fast in air, that its resistance will increase greatly in time. I want to be an electrical engineer so I would like to know if this is true, because I feel it is important.

Adrianspeeder

[adrianspeeder]

I was taught that pure silver was a better conductor than gold, but it tarnishes so fast in air, that its resistance will increase greatly in time. I want to be an electrical engineer so I would like to know if this is true, because I feel it is important.

Adrianspeeder

[Anonymous]

Hey, Kev - no problem.

I was just trying to clarify some of the involved phenomena - those two web sites I gave links for pretty much describe it.

- - - - - - -

As for signals - I don't know how they do it today, or in other locations, but when I was in college (late '60s) we knew of a grade crossing near Ann Arbor Michigan where shorting one rail to the other near the crossing set off the signals. (OK - I was one of those "kids" I mentioned.) Indeed, with metal wheels and axels, trains "short" the two rails... complete a connection ( just like turning on a light switch completes a connection) for the signal-control and the signal goes off. We walked up and down the rails, and found the point beyond where the signal no longer went off when shorted - there was a point there where the rail continued on after a small gap formed by the two rail sections not quite touching. I'm sure there was a similar gap a similar distance away from the crossing in the other direction, leaving this section of rail several hundred yards either direction from the crossing which was connected by a wire to the signal control box (we located the wire) and the opposite rail also was connected by another wire to the box.

Then they put a relatively low voltage difference on the two wires, and anything shorting the rails completed the circuit and current flowed (through a relay no doubt back in 1965 - perhaps an electronic circuit today) and the crossing signal activated. We didn't measure the voltage - we should have to make the experiment complete.

I expect the presence of a train in a block is sensed in a similar way, so the dispatcher's displays and the block signals can react appropriately.

Hey, now - it wasn't vandalism. We were young Electrical Engineering majors, it was a low-traffic area, and it was late at night. We were conducting "experiments" to see how it all worked. :-)

- - - - - - -

In the late '70s I worked for Dayton Power and Light Company - I know they have arrestors on the power lines. Have you ever noticed in a thunder storm when you are in your house and lightning strikes somewhere in your neighborhood and your house lights go off for a fraction of a second? That's the arrestor shorting the lightning pulse (and the power-company-supplied AC) to ground momentarily. After the lightning strike dissipates, the arrestor opens up (simple power-company-supplied AC isn't enough voltage to arc the gap) and you resume receiving AC to your house.

- - - - - - -

Page two, paragraph three of the NASA site I referred to has the 3x temperature of sun's surface item (the paragraph on thunder).

- - - - - - -

You guys keep posting the marvelous train-related info here! This is a fascinating board. I've been a radio/electronics/computer/photography nut for most of my 58 years, but only recently bitten by the railfan bug - I got it from my grandson. I kick myself for not paying attention to trains when I was young - steam was still in regular commercial service and I was oblivious! What a shame.

Chuck Somerville

[Anonymous]

Hey, Kev - no problem.

I was just trying to clarify some of the involved phenomena - those two web sites I gave links for pretty much describe it.

- - - - - - -

As for signals - I don't know how they do it today, or in other locations, but when I was in college (late '60s) we knew of a grade crossing near Ann Arbor Michigan where shorting one rail to the other near the crossing set off the signals. (OK - I was one of those "kids" I mentioned.) Indeed, with metal wheels and axels, trains "short" the two rails... complete a connection ( just like turning on a light switch completes a connection) for the signal-control and the signal goes off. We walked up and down the rails, and found the point beyond where the signal no longer went off when shorted - there was a point there where the rail continued on after a small gap formed by the two rail sections not quite touching. I'm sure there was a similar gap a similar distance away from the crossing in the other direction, leaving this section of rail several hundred yards either direction from the crossing which was connected by a wire to the signal control box (we located the wire) and the opposite rail also was connected by another wire to the box.

Then they put a relatively low voltage difference on the two wires, and anything shorting the rails completed the circuit and current flowed (through a relay no doubt back in 1965 - perhaps an electronic circuit today) and the crossing signal activated. We didn't measure the voltage - we should have to make the experiment complete.

I expect the presence of a train in a block is sensed in a similar way, so the dispatcher's displays and the block signals can react appropriately.

Hey, now - it wasn't vandalism. We were young Electrical Engineering majors, it was a low-traffic area, and it was late at night. We were conducting "experiments" to see how it all worked. :-)

- - - - - - -

In the late '70s I worked for Dayton Power and Light Company - I know they have arrestors on the power lines. Have you ever noticed in a thunder storm when you are in your house and lightning strikes somewhere in your neighborhood and your house lights go off for a fraction of a second? That's the arrestor shorting the lightning pulse (and the power-company-supplied AC) to ground momentarily. After the lightning strike dissipates, the arrestor opens up (simple power-company-supplied AC isn't enough voltage to arc the gap) and you resume receiving AC to your house.

- - - - - - -

Page two, paragraph three of the NASA site I referred to has the 3x temperature of sun's surface item (the paragraph on thunder).

- - - - - - -

You guys keep posting the marvelous train-related info here! This is a fascinating board. I've been a radio/electronics/computer/photography nut for most of my 58 years, but only recently bitten by the railfan bug - I got it from my grandson. I kick myself for not paying attention to trains when I was young - steam was still in regular commercial service and I was oblivious! What a shame.

Chuck Somerville

[edblysard]

By the way, Kev,
One of the ways you can tell who a real gentleman is when he is man enough to reconize he has made a mistake, and how he goes about rectifing the mistake.
Good job, Sir.
Ed

[edblysard]

By the way, Kev,
One of the ways you can tell who a real gentleman is when he is man enough to reconize he has made a mistake, and how he goes about rectifing the mistake.
Good job, Sir.
Ed

[Anonymous]

okay it seems i have come under fire with my posts, Rereading the comments of... Csomervi i took one of his statements as a personal attack and got well somewhat angry.. or very angry and started name calling, which i should not have done.. seen where trhis goes before mine as well make up amenze before i get too many people angry at me.

Life is to short to be angry at people, And to become so angry at A misunderstood coment really brings to light the immaturity still in me, I use no excuse to justify that behavior, nor am i going to pin the blame on a misunderstanding.

And i tell you all who read this, you should all go out AND DESTROY your enemies right now! Abraham Lincoln, Once said, "I destroy my enemies by making them my friends." That is the only way to Destroy your Enemy.

on that note, i offer my apologies too... CsomeRVI.. i am sorry for misunderstanding you, and taking your coments in a completely opposite way for which they were originally intended.

[Anonymous]

okay it seems i have come under fire with my posts, Rereading the comments of... Csomervi i took one of his statements as a personal attack and got well somewhat angry.. or very angry and started name calling, which i should not have done.. seen where trhis goes before mine as well make up amenze before i get too many people angry at me.

Life is to short to be angry at people, And to become so angry at A misunderstood coment really brings to light the immaturity still in me, I use no excuse to justify that behavior, nor am i going to pin the blame on a misunderstanding.

And i tell you all who read this, you should all go out AND DESTROY your enemies right now! Abraham Lincoln, Once said, "I destroy my enemies by making them my friends." That is the only way to Destroy your Enemy.

on that note, i offer my apologies too... CsomeRVI.. i am sorry for misunderstanding you, and taking your coments in a completely opposite way for which they were originally intended.

[Puckdropper]

If you watch sometimes, lightning will flash 7-8 times in a row. This means it's found a good place to ground...

[Puckdropper]

If you watch sometimes, lightning will flash 7-8 times in a row. This means it's found a good place to ground...

[edblysard]

Wow,
Hey Kev, take a deep breath and chill for a minute.
You know me, sorta, so you know I dont tell lies.
My train was hit, twice within seconds.
Down here on the gulf coast, we see summer thunderstorms almost daily.
We were pulling a track out to switch, and a bolt hit a UP reefer twice, once on the frame that holds the compressor and heat exchanger, and once on the roof.
It tripped the ground relay on the locomotive, and blistered the paint off the roof of the car. The frame had a small piece, about two inches long, that looked like a drunk welder tried to cut it off.
And it was quick, all we heard was a double boom! and the locomotive quit loading.
At first, we though we had busted something in the engine, but when my engineer reset the ground relay, every thing worked fine.
It wasnt until we were shoving back into the yard that the yardmaster told us we had been hit, (he had seen it from the tower) and which car had been hit.
Down here, all the high power line pylons have a additional ground rod attached to them, because their legs sit in huge concrete pileings and do not offer a good ground.

Was watching a program about lightning on the Discovery channel a few weeks back, and part of the program discussed the fact that, occasionaly the earth sends up a small charge they refered to as a leader or feeler charge, as if it was trying to attract a strike.
They captured this on film, it shows up a micro scecond before the strike, reaching upwards like a small ribbon about 4 to 6 feet long.
Without going into a lot of the techno poop, it seem that some clouds create a large magnetic field which makes electrons line up underneath it in some objects. This in turn creates a static charge opposite the charge of the cloud, and as the cloud get closer or lower, the charge flows up any object it can, trying to get to the cloud from ground, creating the feeler or leader.
They captured this several times, coming from trees, the edge of buildings, and power poles.
One of their examples was of a old oak tree in a farm yard.
Lightning struck it, instead of the higher grain silo right next to it, because the tree had built up a stronger charge, and sent out this feeler, which offered a better ground for the lightning that the silo.
Which do you think lightning would strike, the concrete silo, or the oak tree thats already sending up a weak opposite charge?
Which might explaine why the guy who posted that his plum tree was hit, while the oak nextdoor wasnt, the plum tree had a charge already.

Yes, lightning does strike the same place twice, in fact, most lightning strikes are multiple strikes in the same place, the lightning pulses or cycles like A/C, not only is the cloud discharging, the ground or earth is also discharging its charge up the path of least resistance.

And once lightning had moved through the air, its path offeres a new path of lesser resistance for following strikes, most of the air and rain(water) molecues have been moved out of the way already, so the cloud, if its charged enough, will discharge down that path again.

It was a very interesting program, one I would recommond anyone who works outdoors watch, it even covered whats know as clear air lightning, where a lightning strike occures out of a almost cloudless sky. They had a young lady on the show, who was sitting on the edge of a small rise in her desert home, and was hit out of the blue by a bolt of lightning.
Seems that enough charge had built up in the single cloud in the sky to the point it discharged into the highest thing on the ground, which happened to be her.

Wow, another reason not to take up golf!

Ever been out in the rain, and feel all the hairs on your arms and the nape of your neck suddenly stand up?
According to the guys on the show, you have built up a good static charge, or are standing on or in a static charge, and are offering the highest point for the static charge to reach up towards the oppositely charged clouds.
Which makes you a pretty good target for a lightning strike, a human lightning rod, so to speak.

Wow, a second reason not to take up golf!

Stay Frosty,
Ed

[edblysard]

Wow,
Hey Kev, take a deep breath and chill for a minute.
You know me, sorta, so you know I dont tell lies.
My train was hit, twice within seconds.
Down here on the gulf coast, we see summer thunderstorms almost daily.
We were pulling a track out to switch, and a bolt hit a UP reefer twice, once on the frame that holds the compressor and heat exchanger, and once on the roof.
It tripped the ground relay on the locomotive, and blistered the paint off the roof of the car. The frame had a small piece, about two inches long, that looked like a drunk welder tried to cut it off.
And it was quick, all we heard was a double boom! and the locomotive quit loading.
At first, we though we had busted something in the engine, but when my engineer reset the ground relay, every thing worked fine.
It wasnt until we were shoving back into the yard that the yardmaster told us we had been hit, (he had seen it from the tower) and which car had been hit.
Down here, all the high power line pylons have a additional ground rod attached to them, because their legs sit in huge concrete pileings and do not offer a good ground.

Was watching a program about lightning on the Discovery channel a few weeks back, and part of the program discussed the fact that, occasionaly the earth sends up a small charge they refered to as a leader or feeler charge, as if it was trying to attract a strike.
They captured this on film, it shows up a micro scecond before the strike, reaching upwards like a small ribbon about 4 to 6 feet long.
Without going into a lot of the techno poop, it seem that some clouds create a large magnetic field which makes electrons line up underneath it in some objects. This in turn creates a static charge opposite the charge of the cloud, and as the cloud get closer or lower, the charge flows up any object it can, trying to get to the cloud from ground, creating the feeler or leader.
They captured this several times, coming from trees, the edge of buildings, and power poles.
One of their examples was of a old oak tree in a farm yard.
Lightning struck it, instead of the higher grain silo right next to it, because the tree had built up a stronger charge, and sent out this feeler, which offered a better ground for the lightning that the silo.
Which do you think lightning would strike, the concrete silo, or the oak tree thats already sending up a weak opposite charge?
Which might explaine why the guy who posted that his plum tree was hit, while the oak nextdoor wasnt, the plum tree had a charge already.

Yes, lightning does strike the same place twice, in fact, most lightning strikes are multiple strikes in the same place, the lightning pulses or cycles like A/C, not only is the cloud discharging, the ground or earth is also discharging its charge up the path of least resistance.

And once lightning had moved through the air, its path offeres a new path of lesser resistance for following strikes, most of the air and rain(water) molecues have been moved out of the way already, so the cloud, if its charged enough, will discharge down that path again.

It was a very interesting program, one I would recommond anyone who works outdoors watch, it even covered whats know as clear air lightning, where a lightning strike occures out of a almost cloudless sky. They had a young lady on the show, who was sitting on the edge of a small rise in her desert home, and was hit out of the blue by a bolt of lightning.
Seems that enough charge had built up in the single cloud in the sky to the point it discharged into the highest thing on the ground, which happened to be her.

Wow, another reason not to take up golf!

Ever been out in the rain, and feel all the hairs on your arms and the nape of your neck suddenly stand up?
According to the guys on the show, you have built up a good static charge, or are standing on or in a static charge, and are offering the highest point for the static charge to reach up towards the oppositely charged clouds.
Which makes you a pretty good target for a lightning strike, a human lightning rod, so to speak.

Wow, a second reason not to take up golf!

Stay Frosty,
Ed

[Anonymous]

i am by far no expert however i do know, believe it or not lightning strikes 2 ways one of from cloud to cloud the other is from the ground up yeah thats right lightning strikes up not down remember electron flow the earth has a negative charge you must also remember lightning like any other voltage is realative to somehting. static electricity looks for a diffrence of potential thats how it can go from cloud to cloud they may both be positive compared to the earth however one may be negative when compared yo the other, hence the diffrence of potential. i agree train tracks are not the best ground being located on a bed of gravel and the main part touching the ground is the wooden tie however i do know lighting hit the 779 and i dont doubt that it hit the AC 4400 dkemd mentioned i do not know why it strikes where it does i dont know why it struck a 15 foot peach tree in my back yeard instead of a 70 foot oak in my neighbors it is however one of natures most intriguing phenomena ask a golfer. i hear they get struck by lighting 300 times a year or more i wonder how many lighting strikes a pair of golfers pants are good for ?

[Anonymous]

i am by far no expert however i do know, believe it or not lightning strikes 2 ways one of from cloud to cloud the other is from the ground up yeah thats right lightning strikes up not down remember electron flow the earth has a negative charge you must also remember lightning like any other voltage is realative to somehting. static electricity looks for a diffrence of potential thats how it can go from cloud to cloud they may both be positive compared to the earth however one may be negative when compared yo the other, hence the diffrence of potential. i agree train tracks are not the best ground being located on a bed of gravel and the main part touching the ground is the wooden tie however i do know lighting hit the 779 and i dont doubt that it hit the AC 4400 dkemd mentioned i do not know why it strikes where it does i dont know why it struck a 15 foot peach tree in my back yeard instead of a 70 foot oak in my neighbors it is however one of natures most intriguing phenomena ask a golfer. i hear they get struck by lighting 300 times a year or more i wonder how many lighting strikes a pair of golfers pants are good for ?

[Anonymous]

I agree with zardoz and cosmi. I was a welder for 7 years and that short lillte arc (between 200 and 650 amps...mig, submerged arc is even higher in amperage) can be in excess of 10,000 degrees F.
Kev, chill out. I tend to be a little fiery myself, but, when I flame an old head, I usually end up looking like the ***.
Ken

[Anonymous]

I agree with zardoz and cosmi. I was a welder for 7 years and that short lillte arc (between 200 and 650 amps...mig, submerged arc is even higher in amperage) can be in excess of 10,000 degrees F.
Kev, chill out. I tend to be a little fiery myself, but, when I flame an old head, I usually end up looking like the ***.
Ken

[dekemd]

QUOTE: Originally posted by kevinstheRRman
[ top line emeits a magnetic field, and whats this Bull about a static electricity, which plays no role, FOR THE RECORD, power lines are the least likely to get struck by lightning

Lightning is static electricity. It's like walking across carpet then getting zapped by the door knob, just on a much, much larger scale.

Derrick

[dekemd]

QUOTE: Originally posted by kevinstheRRman
[ top line emeits a magnetic field, and whats this Bull about a static electricity, which plays no role, FOR THE RECORD, power lines are the least likely to get struck by lightning

Lightning is static electricity. It's like walking across carpet then getting zapped by the door knob, just on a much, much larger scale.

Derrick

[zardoz]

Kevin-
FYI
Regarding the temperature of lightning, the statement about lightning being three times hotter than the sun is a conservative number. The surface of the sun averages about 10,000 degrees Farenheit, whereas the temperature of lightning can reach 50,000 degrees Farenheit, FIVE times hotter than the surface of the sun.


And your derogatory comments directed towards the other posts that you quoted are quite unnecessary and are not welcome. [V]

Come on Kevin, you've done some quality posts and comments before, why resort to name calling?

[zardoz]

Kevin-
FYI
Regarding the temperature of lightning, the statement about lightning being three times hotter than the sun is a conservative number. The surface of the sun averages about 10,000 degrees Farenheit, whereas the temperature of lightning can reach 50,000 degrees Farenheit, FIVE times hotter than the surface of the sun.


And your derogatory comments directed towards the other posts that you quoted are quite unnecessary and are not welcome. [V]

Come on Kevin, you've done some quality posts and comments before, why resort to name calling?

[Anonymous]

QUOTE: Originally posted by csomervi

It's not about "magnetic" charges - it's "static" electricity - electrical potential - voltage differences - between the cloud and ground.

The voltage necessary to generate that huge (3 times hotter than the sun) arc discharge between cloud and ground is hundreds of thousands (or even millions) of volts.

Three times hotter then the sun? Never heard that before evn on the discovery channel!

QUOTE:

Power lines are indeed struck with some frequency - they are often higher than the surrounding conductors, and regardless of what charge the power company puts on them (which is by the way AC not DC so it's neither always positive nor always negative)

top line emeits a magnetic field, and whats this Bull about a static electricity, which plays no role, FOR THE RECORD, power lines are the least likely to get struck by lightning

QUOTE:

Tracks might as well be ground. Whatever signal-activating voltage is there is low (24 volts or less is my guess - kids don't get electrocuted shorting tracks together with a length of wire to see the crossing signals go on)

Wow, that is Stupid, see Trains have Axels, and the wheel one one track is connected to the wheel on the other track, if those were opposite charges, we'ed be crap out of luck and be shorting everyhting out every time a train goes over the tracks.. Wow, obviously not troubled with the smarts are we?

QUOTE:

The anecdotes 2 or 3 others have posted here about lightning-struck engines in their shops within the last few months would seem to indicate it happens a bit more frequently than lottery winning. From NASA... "Typically, more than 2,000 thunderstorms are active throughout the world at a given moment, producing on the order of 100 flashes per second."

[red] you know, i may not like Cabforward a heck of alot, but what Him and I do know is that the chances of a train being struck by lightning are slim to none, okay jack sprat?

[Anonymous]

QUOTE: Originally posted by csomervi

It's not about "magnetic" charges - it's "static" electricity - electrical potential - voltage differences - between the cloud and ground.

The voltage necessary to generate that huge (3 times hotter than the sun) arc discharge between cloud and ground is hundreds of thousands (or even millions) of volts.

Three times hotter then the sun? Never heard that before evn on the discovery channel!

QUOTE:

Power lines are indeed struck with some frequency - they are often higher than the surrounding conductors, and regardless of what charge the power company puts on them (which is by the way AC not DC so it's neither always positive nor always negative)

top line emeits a magnetic field, and whats this Bull about a static electricity, which plays no role, FOR THE RECORD, power lines are the least likely to get struck by lightning

QUOTE:

Tracks might as well be ground. Whatever signal-activating voltage is there is low (24 volts or less is my guess - kids don't get electrocuted shorting tracks together with a length of wire to see the crossing signals go on)

Wow, that is Stupid, see Trains have Axels, and the wheel one one track is connected to the wheel on the other track, if those were opposite charges, we'ed be crap out of luck and be shorting everyhting out every time a train goes over the tracks.. Wow, obviously not troubled with the smarts are we?

QUOTE:

The anecdotes 2 or 3 others have posted here about lightning-struck engines in their shops within the last few months would seem to indicate it happens a bit more frequently than lottery winning. From NASA... "Typically, more than 2,000 thunderstorms are active throughout the world at a given moment, producing on the order of 100 flashes per second."

[red] you know, i may not like Cabforward a heck of alot, but what Him and I do know is that the chances of a train being struck by lightning are slim to none, okay jack sprat?

[Anonymous]

It's not about "magnetic" charges - it's "static" electricity - electrical potential - voltage differences - between the cloud and ground.

The voltage necessary to generate that huge (3 times hotter than the sun) arc discharge between cloud and ground is hundreds of thousands (or even millions) of volts.

Power lines are indeed struck with some frequency - they are often higher than the surrounding conductors, and regardless of what charge the power company puts on them (which is by the way AC not DC so it's neither always positive nor always negative) they are close to ground compared to the charge the cloud is unleashing. They have spark-gap lightning arresters which arc over and take the brunt of the strike to ground (so most of it does not end up coming into everyone's house).

Tracks might as well be ground. Whatever signal-activating voltage is there is low (24 volts or less is my guess - kids don't get electrocuted shorting tracks together with a length of wire to see the crossing signals go on) and is not relevant to the attractiveness of them as a ground-like target. They have 6" metal spikes driven into the dirty and wet (it's raining, remember) ties sitting on dirty and wet ballast sitting on ground. It may not exactly be zero ohms from the point of contact on the rail to earth, but the rails conduct and those spikes and ties up and down several hundred yards of the line make a pretty good ground. The lightning struck through a few thousand feet of air so that last few inches of ties and ballast looks pretty good as a conductor by comparison. Put a metal, 16-foot-high, steel-wheeled train on those rails and in open areas it's a juicy target.

The anecdotes 2 or 3 others have posted here about lightning-struck engines in their shops within the last few months would seem to indicate it happens a bit more frequently than lottery winning. From NASA... "Typically, more than 2,000 thunderstorms are active throughout the world at a given moment, producing on the order of 100 flashes per second."

Clouds are usually negative and the ground under them becomes positive in response so the strokes are "down" but a non-trivial minority of strokes are between positive cloud tops and correspondingly negative ground below.

Two good references follow. The first is long but thorough - the 2nd of its 4 pages is particularly descriptive. The second reference is shorter if you don't have patience for the first.

---

http://thunder.msfc.nasa.gov/primer/

http://www.lightningsafety.noaa.gov/science.htm

---

- Chuck Somerville