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During part of
our regular lightning shows the demonstrator raises the cage so that
it will be struck by the sparks. We do this to demonstrate why it is
safe to be in a car during a lightning storm. Most people believe
that the reason has to do with the rubber tires, rubber being an
insulator. Air is also an
insulator, however, and almost as good a one as rubber! If a
lightning bolt has just travelled two or more miles through air, an
inch or two of rubber will not make much difference. Indeed, it has
been calculated that you would need solid tires about a mile thick to
be safe!
However, that
is not needed as there is a more effective protection involved. In a
car you are sitting in a metal box (this is not true in a convertible
or plastic/fiberglass car, and these are not safe). That is
the source of your safety. Many people who know that it is the metal
not the tires assume that the car forms a Faraday
Cage, but that is also not the reason. Faraday Cages work with
static electricity, lightning
bolts are anything but static! The real reason is something called
the skin effect.
In fact, not
only are you safe inside the car, even the inside of the metal car
BODY is safe, a fact we demonstrate by touching the inside of the
cage bars while it is being struck. The outside is not safe,
however, so if your hand were to go through the bars you would get
struck (something that has happened to several of us at one time or
another--it hurts a lot, like hitting your funny bone but about ten
times worse--though the current
is so low that there is no permanent damage. The hardest thing for
the demonstrator in such cases is to remember not to say something
bad since the microphone is still on!
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