Lightning strikes aren't *well* understood, but getting better.
Every item, tree, person, etc generates a "leader" which if viewed via photography shows up like a small electrical string of voltage extending upwards from the object to the sky just before and during lightning activity.
The better grounded and the closer to the source (usually clouds, but not always straight up), usually the longer and thicker the leader.
Common theory is that the first leader to reach close enough to the source (down reaching voltage- lightning) draws the lightning to the object.
As such, the 'tires protect you' discussion isn't as simple as providing a gap which the voltage will easily cross (I think it is something like 50kv to jump one inch of air, amps don't matter). It is also related to the leader produced, and how it compares to those produced by other objects.
That's why higher trees, lightning rods, etc usually get hit instead of a person. Also explains why open fields are a bad idea- you are on a tractor maybe 3 or 4 feet higher than the ground, insulated from the ground, but the grass is probably touching other spots on the tractor.
Remember that a static charge travels (resides) on the outside of an object, not through it. That is why rubber is an insulator, but a good conductor of static. (Ever rubbed a balloon in your hair and stuck it to a wall?)
It is also theorized that static charge is a major source of leaders, since there obviously isn't any direct connection between the object and the sky, to make standard voltage.
Yes, for purists, electrical voltage and static electricity are essentially the same, but act very differently. Sort of like different states of the same material. Solid water (ice) moves differently than liquid water, which flows quite nicely. Not the same thing, but helps one visualize the difference.
Anyway, getting pretty deep into this. Didn't intend to make this a course on electrical theory, just wanted people the remember that even though you think you are protected, when in an open field, your leader is competing with BLADES OF GRASS. Which do you think will win?
This also explains why being in a car is a GOOD IDEA in a storm. Usually no blades of grass, etc rubbing against metal of car generating static and the water usually carries the static charges away from the car, so usually not big leaders generated. The common "rubber tires of a car protect you from lightning" advice statistically holds true, but not for the reason most people think.
Oh yeah, sources of lightning aren't all straight up. It may "jump" from sky to top of silo to barn roof to metal sheet wall to tractor next to it to you!
Don't trust it. Sometime look up "blue sky lightning", which occurs without any storm clouds.
For more info about static and just cool stuff, check out "Kelvin's Thunderstorm" on this page. Most of the links are broken now, but scroll down to the diagrams.
http://www.rdrop.com/~cary/html/high_voltage.html
Stay dry, don't die /forums/images/graemlins/smirk.gif
-JC
