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Re: meteorite-impact physics item


geozay>When I wrote this I was going by memory. I just looked it up. It took 2
>minutes and 46 seconds for the sonic boom to reach us from the time of the
>meteor's appearance. But a sonic boom occuring 4 minutes after a fireball's
>appearance isn't unusual either. In fact, up to several minutes after the
>meteor's appearance has been reported. Well within the range of what you 
>think won't happen.<<

Baalke>>OK, that puts it closer, but the fireball is at a distance
of about 50 miles.  According to Richard Norton, an observer should be able
to hear sonic booms from a distance of up to 25 to 30 miles.<<

Also the given altitude above the earth that a fireball must reach in order
for it to produce a hearable sonic boom is often given at around 30 miles.
In D.W.R McKinley's book on Meteor Science and Engineering on page 141 he
says, "Below about 50 km sounds may be heard, first the sharp crack of the
shock wave created by the supersonic object and then a rumbling sound similar
to thunder as the air fills in the hole that the body literally bores thru the
atmosphere. These sounds travel at a speed near 330 m/sec; hence several
minutes may elapse between the passage of the meteor and the arrival of
sound". 
George Zay