Ask A Scientist Weather Archive

name         Michael C.
status       other
age          40s

Question -   I know your web page states the speed of lightning is
about 186,000 miles per sec, however there are other web sites that
claim half the speed of light and even one third the speed of light. I work at
a news station and a debate goes on here over the speed of lightning.
Any light you may shed on this would be most appreciated.
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I believe that the response of 186,000 miles/sec is a misunderstanding,
and refers to the "speed of light" which is very different than what I think
you are asking about. I assume that you mean what is the speed of a
lightning discharge from cloud-to-ground, ground-to-cloud, or
cloud-to-cloud. That is a much more complicated question to answer because
it depends upon the path and speed that the atmospheric plasma advances and
that depends upon many factors. The web site:
http://wsx.lanl.gov/Publications/lightning_bolt.html
gives a rather in-depth analysis of the question.

Vince Calder
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Michael,

Actually, someone asked this question of our
web site a while ago and the answer is posted.

However, the speed is normally no more than half
the speed of light, usually substantially less.

The process that creates a lightning stroke is
not light transfer, but is the transfer of
electrical energy (charge) through
the air. Much like an electrical cable, the air,
even though it is ionized, has some resistance
to charge transfer. The speed of the stroke is
impeded by having to transfer the energy from
molecule to molecule along the way, in the process
literally exploding the molecules into atoms.

David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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Michael C.,

Per the MEDICAL MYSTERIES LIGHTNING STRIKES video put out by the Discovery Channel 
(2000 Publication), it states that lightning travels at a rate of 60,000 miles a second.  
I hope that this helps.

Sincerely,

Bob Trach
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