Yes. A rapid expansion and collapse of air pressure would most definitely be inseparable causes.
~Kyle
On Wed, Feb 6, 2008 at 10:30 AM, Andy Farnell padawan12@obiwannabe.co.uk wrote:
Yes. That's part of it.
According to Ribner and Roys first paper the vacuum collapse model is refuted - well, they don't use that exact word - more like they suggest it is replaced...
"As recently as the late 1800's, four theories of thunder were in competition: The vacuum collapse theory, the explosive electrolysis theory (recombination of electrolyzed water), the steam expansion theory, and the Ohmic heating theory (resistive heating and consequent expansion due to heavy current discharge). The last, proposed by M. Hirn in 1888, is now accepted, being supported by a large body of consistent experimental data and theory."
However I disagree, since it is one necessary flip side of the favoured primary cause - collapse happens after the expansion (in a remarkably short time frame) Therefore the vacuum collapse theory must be incorporated into a complete model, being responsible for the negative impulse of the N-wave.
"One prevailing theory proposed that thunder was produced when lightning, passing through the air, caused a vacuum to form. When this vacuum collapsed, the air rapidly rushing back in produced a thunderous explosion."
http://www.islandnet.com/~see/weather/elements/thunder1.htm
As I see, the unipolar vacuum collapse theory only makes sense, if there is a chemical reaction that removes CO2, H2O, O2 or N2 from the atmosphere, (and one assumes no matter is transformed to energy) - well NO2 and O3 are produced, but that doesn't account for the volume.
Vacuum collapse theory ?? (< 1800) Steam theory of R.V. Reynolds (1903) Electrolysis theory R.S. Mershon (1870) Ohmic heating theory M. Hirn in 1888
In a 1888 article in Scientific American, M. Hirn advanced the theory that
"thunder is due simply to the fact that the air traversed by an electrical spark, that is, a flash of lightning, is suddenly raised to a very high temperature, and has its volume, moreover, considerably increased. The column of gas thus suddenly heated and expanded is sometimes several miles long, and as the duration of the flash is not even a millionth of a second, it follows that the noise burst forth at once from the whole column, though for a observer in any one place it commences where the lightning is at the least distance....the beginning of the thunderclap gives us the minimum distance of the lightning, and the length of the thunder clap gives us the length of the column."
So, in summary, there is no single cause and all these theories are sensibly incorporated into the process.
Least likely is perhaps Mershon - but in a plasma we know the gasses are monatomic and there is still a lot of stuff to be discovered in plasma physics, so he may have been on to something after all.
Reynolds clearly contributes something sensible, because water vapour has the highest thermal expansive coefficient.
And the vacuum collapse theory _must_ be incorporated if the Ohmic expansion theory holds.
a.
On Wed, 6 Feb 2008 16:00:58 +0100 plessas@mur.at (Peter Plessas) wrote:
- Andy Farnell padawan12@obiwannabe.co.uk [2008-02-05 23:33]:
You're spot on there. I will develop the stereo image as I work on the environment model.
But interestingly enough, lightning _is_ an explosion, one hell of a big explosion. The plasma is as hot as the Sun for an instant and that's why the air expands, the energy in a lightning bold makes most bombs seem like little fireworks. The difference is, and this is unusual, it radiates in a cylinder not a sphere, and sound comes from a simultanoeus extent (because the bolt moves at the speed of electricity which is closer to the speed of light than the speed of sound)
Isn't the noise happening when the light/plasma channel is collapsing after the lightning happened?
regards, Peter
PD-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
-- Use the source
PD-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list