Water and Lightning
When lighting hits water (ocean) how many miles are
effected by the electrical path
This is a very good question, which is not easy to
answer. I know of no measurements of this. However,
the horizontal distance that the lightning energy would
travel across the surface would depend on the intensity
(current) of the lightning and how deep the water is
where the stroke hit the water. Water is a fairly good
conductor of electrical energy. If you dropped a 120 volt
AC line into an 18 foot diameter, 3 foot deep home swimming
pool, you very well may be killed. In the case of lightning,
multiply the electrical current by thousands, and for the ocean
multiply the volume by as much as millions.
My guess is that the average lightning strike would electrify
a few hundred feet worth of water from it's strike point
sufficiently to electrocute someone. However, some current
is probably for up to a mile before it is fully dissipated.
Great question. Thanks Brian.
Lightning researcher at Argonne National Laboratory
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Update: June 2012