A little late with this because I have been in New York City at a meeting.  It was an important enough meeting that I missed the race on Sunday.  I was sad to read Monday that a race fan was killed by a lightening strike (and nine others were injured) at the Pocono racetrack after the race.  Outdoor sports face a very specific threat from lightening that is difficult to manage.  Here’s why:

Lightning

Lightning is an extremely powerful phenomenon that arises because  there are two types of electrical charge and they don’t like being separated for very long.  An atom can have a negative charge (which means more electrons than protons) or a positive charge (which means fewer electrons than protons).  During a thunderstorm, charges within a cloud can be forced apart, creating a large electric field between the top and the bottom of the cloud, and a slightly smaller field between the bottom of the cloud and the ground.

As charge continues to separate, the charges start to feel crowded – remember that like charges repel, so the charges move as far away from each other as possible – but they are limited because they can’t escape the cloud.

Charges need a path in order to flow.  Electricity flows through some materials much better than through other materials.   Electrons flow in a circuit because copper wire offers very little resistance to their motion.  The electrons would much rather move along the copper wire than through the rubber that covers the wire — or through the air.  Air, in fact, is a really good electrical insulator.

So the charges keep building up and building up on the cloud.  Eventually, they build up so strongly that they can overcome the resistance of the air and travel from the cloud to the Earth.

This is the same phenomenon (in principle, not magnitude) as when you shuffle your feel along a carpet in the winter and get a shock from the doorknob.  The shuffling (rubbing your shoes or foot along the carpet) charges you up.  When you’re standing in the middle of the room, the charges aren’t capable of getting through the air.  When you reach for a doorknob, you get to a point where there is so little air between you and knob that the excess charges on your fingers jump from you to the metal doorknob and you get a shock.

Think about a doorknob in the winter.  You shuffle your feet along a carpet, which causes charges to build up on your skin.  The more you shuffle, the more charges you add and the more unhappy the charges are being crammed together.  When you reach for a doorknob, you can get close to the doorknob and the charges can literally jump from you to the doorknob.

The same thing happens with a charged cloud.  At some point, the charges have just had it with each other and they have to find some way to get away.  About 3/4 of the time, the charges are redistributed within the cloud.  The other 1/4 of the time, the charges head for the ground.  We’re talking enormous numbers of charges.  A typical lightening bolt has a current of 30,000-100,000 Amperes at more than a billion Volts.   The biggest circuit breaker most of us have in our houses is 40 Amps.  The power contained in a lightening storm is 30,000,000,000,000 Watts, which is 30,000 GigaWatts (GW).  That is the power of 30 billion 100-W light bulbs.  In comparison, the average power consumption of the first stage of the Saturn V rocket is 190 GW and the average hurricane has 50,000 to 200,000 GW.  Lightening is not trivial, nor should it be ignored.

Be Safe

Understanding how electricity works helps you understand how to avoid danger.

• For example, you may have noticed that you get shocked in the winter only when you touch a metal doorknob and not a glass door knob.  Electricity likes electrical conductors, like metals, much more than electrical insulators, like rubber or air.
• Electricity looks for the shortest path.  The closer something is to the cloud, the easier it is for electrons to make the jump from the cloud to the object
• Electricity like points.  The best explanation I’ve seen of this fact uses the analogy of a choir distributed along a piece of wire, with the choir being electrons and the sound being the electric potential.  What’s important for the rest of the argument is that electrons like points.

Consider the situation at left, which a cloud just about to let loose.  Which one of those targets looks the most likely to be struck?  Probably the lightening rod at the top of the tall building in the middle.  If that building weren’t there, it would be the tree.  Look at the three points above and you’ll understand why lightening rods are shaped and positioned the way they are.

The key to safety in a storm is making sure that you are not the tallest object in the area.  And that you are not standing under the tallest object in the area.  Avoid trees, utility poles, and anything metal.  Also stay away from water because, although water is not a good electrical conductor compared to rubber or air, it is still an electrical conductor.  Especially when you’re immersed in it.

Hopefully you now understand why ground crews at airports are removed from the tarmac when there is possible lightning in the area.  Standing around a bunch of metal planes with pointy flaps in a lightning storm is a good way to get killed.

Racetracks and Other Sporting Events

A racetrack is a large building with metal grandstands and lots of pointy metal things like flagpoles and billboards jutting into the air.  Fans put up antenna and flagpoles on their RVs and park under lights supported by giant, pointy metal poles.  The fan that was killed was reportedly with their car and had a pop-up canopy (probably metal) behind the vehicle.

It’s just an inherently hard situation in which to protect people from lightning. It’s made more difficult because there are so many people in a relatively small area that you can’t get everyone moved quickly.  There’s also the added danger of people in a panicked crowd trampling each other.

Lightning has long been recognized as a danger at golf courses, and professional tours have rules about the conditions under which play must stop.  NASCAR is re-examining its policies for stopping races due to weather, which has to be done cooperatively with each track.  Personally, I never feel comfortable trusting my safety to someone else.  So if you’re at the racetrack, here’s my advice.

• If you can hear thunder, there is lightning.  You may not see the lightning, but thunder means it is there.  Go indoors.  A number of track promoters have mentioned that no one is going to hear thunder of the cars – and no one is going to hear an announcement from the track over the cars either.
• If you’re in the grandstands, get away from the highest points and take cover indoors.  Bathrooms are good all-purpose shelters.
• If you’re at your car, get in it.

The last one seems wrong, doesn’t it?  A car is metal and often has a pointy antenna, so how does that fit in with the rules outlined above?  The car becomes what we call a Faraday cage.  When you surround a space with a conductor, the charges redistribute themselves all over the surface of the conductor, which means no electricity inside the car.

Weather is an impossible situation to control and we saw the worst case last week.  The folks at Pocono Raceway have set up a fund for the family of Brian Zimmerman and the eight other injured people. Whether you’re at a race track or a picnic, use your head and stay safe.