Date: 02 Oct 2006 08:19:53
From: Paul Schlyter
Subject: Lightning Strikes Observatory
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In article <ebmpco$1mf9$1@merope.saaf.se >, pausch@saaf.se says...
>In article <3o7td256dgm02h2ji96q3dd9g6mtbicbh2@4ax.com>,
>Chris L Peterson <clp@alumni.caltech.edu> wrote:
>
>> On Sat, 12 Aug 2006 22:25:47 -0500, William Hamblen
>> <wrhamblen@comcast.net> wrote:
>>
>>> I would think that the voltages present in lightning would exceed the
>>> breakdown voltage of the dome, making the dome no protection at all
>>> except to keep the rain out. Lightning could blow a hole in a light
>>> weight metal dome.
>>
>> Lightning does blow holes in thin metal- it is fairly common with
>> airplanes, for instance. But it isn't likely to pass through the dome
>> and arc into the interior of the observatory. The current travels on the
>> surface of conductors. That's why you are generally safe inside a car
>
>....except that one isn't quite as safe inside a car as commonly believed.
>True, the metal in the car protects from a lighting strike, but if you're
>unlucky, the gas tank of the car might explode. So if you really want
>to be safe, empty the gas tank first, then ride out the thunderstorm inside
>the car.
Now it happened again: yesterday in Sweden, lightning struck a car with two
people: http://www.aftonbladet.se/vss/nyheter/story/0,2789,897435,00.html
The two people in the car, who felt safe because they sat inside the car,
both lost their hearing, and one of them also got burnt. The dor said
they were lucky to survive. The car started burning.
The lighning expert Vernan Coonray, from Uppsala university, says it's just
a myth that a car is a safe place in a thunderstorm. If a car is hit by
lightning, it's not uncommon that the gas tank explodes or that the front
window gets crushed. The safest place during a thunderstorm is a stone
building with properly installed electric wires which can divert the
lightning into several directions. A barn without electricity gives no
protection at all, the lightning just goes through the roof.
>> (or an airplane) when it is hit by lightning. Even the fiberglass dome
>> affords some protection, since the lightning might find the path of
>> least resistance via the surface. People are not usually hit by
>> lightning inside their houses, even if they have thin, non-conductive
>> roofs.
>> _________________________________________________
>>
>> Chris L Peterson
>> Cloudbait Observatory
>> http://www.cloudbait.com
>
--
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at saaf dot se
WWW: http://stjarnhimlen.se/
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