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From: werme@Alliant.COM (Ric Werme)
Newsgroups: comp.dcom.modems,sci.physics
Subject: Re: TrailBlazer Plus vs. lightning
Message-ID: <3197@alliant.Alliant.COM>
Date: 8 Jun 89 04:11:16 GMT
References: <921@fcs280s.ncifcrf.gov> <204@mipos3.intel.com>
Reply-To: werme@alliant.Alliant.COM (Ric Werme)
Organization: Alliant Computer Systems, Littleton, MA
Lines: 26

In article <204@mipos3.intel.com> bverreau@mipos2.UUCP (stargazer) writes:
>In article <921@fcs280s.ncifcrf.gov> toms@ncifcrf.gov (Tom Schneider) writes:
>> So a better rule is to divide the seconds by 5 to get the distance in miles.

Agreed - that's even what my father taught me.

>But during a lightning storm the barometric pressure is typically lower than
>average.  How would this affect the speed of sound and the conversion rule?

My CRC book doesn't have a decent pressure vs. altitude scale, but is does have
a graph of speed of sound vs. altitude.  Up to 10 km or so, it varies linearly
from 340 M/sec at ground level to 300 m/sec at 10 km.

The face of my altimeter (better than a compass for hiking on mountain trails)
shows pressure falling about 1" of Hg per 1000 ft.  Sorry about mixing units
wildly, but I didn't design them!  Pressure drops in front of thunderstorms are
only fraction of an inch;  lightning 10km. up is far enough away to be boring
unless you're flying a pressurized plane.

Stick to the 5 seconds.

-- 

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