Re: Lightning without thunder?

On Tue, 25 Jul 2006 22:48:34 GMT, Ron Hardin <rhhardin@xxxxxxxxxxxxxx>
wrote:

Al Deveron wrote:

Is there any known kind of lightning flash that doesn't have
accompanying thunder?

I was camping out a few nights ago, and for about 45 minutes, during
the night, I saw intermittent lightning flashes, but saw no lightning
bolt and heard no thunder. The location was in the South West of
England in a rural area on the coast. The lightning flashes were
bright, white, and powerful and seemed in close proximity. It was the
sort of lightning flash that would normally be quickly followed by a
loud crack of thunder.

TIA

Al Deveron

Sound is refracted by for example temperature changes, and there
may be no path for it from the lightning to you.

You get a mathematical surface with sound on one side and no sound
on the other, the sound side hearing two different paths at once.
Called a caustic surface. What happens in its vicinity requires
a wave solution of the acoustic equations (rather than ray tracing).

The refraction is why a jet plane sounds intermittently loud and soft,
as rays of sound are focussed on you and then defocussed as the ray
passes various thermals refracting it.

And then there's what locals here in the Upper Great Lakes of the U.S.
call "heat lightning", where you see the flashes but don't hear the
thunder. "Heat lightning" is really just someone else's thunderstorm,
but you get to see the display and can't hear the cheer. Thunderheads
can be seen, at various latitudes, from in excess of 150km away, and
all of the lightning may be caught up in that after sunset. Pretty
obvious, as brilliant as these displays can be, that sound does not
travel with the same efficiency or distance as light.

Not disagreeing with the above poster, just offering a simpler
explanation.
.

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