Re: [Phys-l] volcano, lightning, frontiers of physics

[Brian Whatcott <betwys1@sbcglobal.net>]

John Denker wrote:
> Here's a cool picture of Eyjafjallajokull, showing lava, 
> billowing ash, and lightning:
>   http://inapcache.boston.com/universal/site_graphics/blogs/bigpicture/eyja_04_19/e01_23056097.jpg
>
> I mention it in this forum because
>  a) It's a cool picture, and
>  b) There is some physics in it.
>
> I recommend this topic as an answer to any student who 
> gets the idea that the frontiers of physics have receded
> to the point where ordinary mortals cannot understand the
> questions, let alone the answers.
>
> This is an example where the question can be understood
> by anyone:  How is lightning produced?
>
> The answer is probably not even very complicated.  We just
> don't know what it is. /snip/

"We", kimosabe?

Friction on a moving insulating belt, or jostling in a powder stream are 
in a similar
class, I suggest. Yesterday, my return from Amsterdam involved a far 
Northern
track towards Norway, turning West to the North of Iceland, and south 
west across
Hudson's Bay before heading to DFW. The dust plume that the track was (I 
suppose)
arranged to avoid was not visible to the eye, though it had again halted 
flights in
Northern England on the day before.   Those silicate particles are hard 
on engines,
no doubt. Reminded me that the story of the four engine flame out in an 
earlier
volcanic plume has been somewhat dramatized, in the retelling.
"They tried and tried to restart, as the airliner plunged from 8 miles 
up..." kind of thing.
The issue is that the restart envelope for a jet involves adequate air 
density and
temperature - so that a restart at 12000 feet is not unexpected - at 
least, if you have
any compressor blades left.   :-)

Brian W