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From: jimb@amd.UUCP (Jim Budler)
Newsgroups: net.physics,net.misc
Subject: Re: Those funny lines
Message-ID: <412@amd.UUCP>
Date: Thu, 11-Oct-84 19:51:12 EDT
Article-I.D.: amd.412
Posted: Thu Oct 11 19:51:12 1984
Date-Received: Sat, 13-Oct-84 07:18:46 EDT
References: <170@hocsj.UUCP>
Organization: AMD, Santa Clara, CA
Lines: 40

...
> I have seen a fair amount of documentary footage showing above ground
> nuclear explosions.  Some seem to have some peculiar vertical, white
> vapor trails before and after the explosion.  The usually go off to the
> left of where the bomb goes off and are very much evenly spaced. 
...

Air can only move and compress at a limited rate when compared to
the speed of the shock wave from the nuclear explosion.  As a result
standing waves ('pressure fronts') are created in the air.  At the
dividing line between the high and low portion of the standing
wave 'clouds' are formed, thus your vapor trails.  

As for the even spacing that is due to the mathematics of the
limiting velocity of the air molecules vs. the pressure front vs.
viewing distance vs. predominating wavelength of viewing light.

The vertical, as opposed to circular, horizontal, etc. is probably a
matter of point of view.  A down shot of the explosion over an even
colored terrain would probably show circular rings.  The shockwave
probably travels to the limit of the atmosphere VERY quickly relative to
the horizontal speed so you aren't as likely to see dome shaped
shock waves. ( Very early, just after ignition, picture might show a
dome pattern).  

Pattern on the left of the mushroom vs. on the right?  I don't know
but perhaps this relates to the position of the sun compared to the
photographer and the mushroom.  Since most of the newsreel photos
come from the same testing grounds, and usually the tests were
probably in the afternoon, the sun would be on the same side
relative to the photographer even for different tests (permanent
photo bunker).

All of this is probably the subject of hundreds of classified
research projects costing gigabucks.
-- 
 Jim Budler
 Advanced Micro Devices, Inc.
 (408) 982-6547
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