Vince_Condella's Blog

With the fire at St. Stephen Catholic Church on the south side of Milwaukee probably due to a lightning strike, it is appropriate that we wrap up our severe weather myth series of blogs on the topic of lightning.  At any one time there are about 2,000 to 3,000 thunderstorms in progress around the world and hundreds of thousands of lightning bolts.  Some of the bolts travel from cloud-to-cloud, others are intracloud (within the same cloud), and still others are cloud-to-ground.

Technically the initial lightning bolt travels upward, with subsequent flashes pulsating down to the ground.  The base of the cloud sends down a bunch of negative charges in a stepped leader.  This trail of electrons travels in steps of about 50 yards in length, with each step taking less than a millionth of a second.  The stepped leader is very fast and impossible for us to see.

As the stepped leader reaches down to the ground, a trail of positive charges moves upward to meet the negative charges.  These postive charges usually gather at the tip of a tall object.  Once the two trails connect, the path has been cleared for electrical current to run from ground to cloud and back again.

The bright return stroke then moves from cloud to ground in 100 millionth of a second.  This is what we traditionally think of as the lightning bolt.  Because it is so bright, its image is burned into our eye and we perceive it to last much longer than it really does.  So the stepped leader travels downward, meets the positive charges moving up from the ground.  Once the path is established, the visible return stroke heads back down again.  It's quite a process.

But are you safe if you are inside a car?  It depends on the car.  Here's the myth-buster: you are not safe because the rubber tires insulate you from the electrical current.  Rubber is a good insulator but so is air.  The lightning bolt just travelled through 1/2 to 1 mile of air to reach your car, so those measely little tires won't stop the surge.  You would need tires about a mile thick to protect you.

Often the tires of a car will melt if it is hit by lightning.  You are protected if the car is metal, all of the windows are closed, and you are not touching any metal objects inside the car.  If the car is hit by lightning, the electrical current will travel around the outside "skin" of the metal car.  Cars made of fiberglass or plastic, or cars that are convertibles, may not offer the proper protection.

Here are links to two You Tube videos that deal with cars being hit by lightning.

Link 1            Link 2

The first link is about 2 minutes long and is from a news report in Canada.  The second link is about 5 minutes long and is from a BBC television show.  Both are interesting, although the Canada report hints that the rubber tires saved the family inside the van.  That is incorrect.  The BBC report claims a car acts as a Faraday cage, but technically that is not true.  The occupants of a car are safe because of the "skin" effect of the automobile.

For a brief but technical explanation of the skin effect, go HERE.

Don't worry, there won't be a test on any of this.  :)  But the whole "rubber tires keeping you safe" myth is one that comes up time and time again.