[AZ-Observing] Noise from meteors. Was: Re: Re: BOLIDE! (photo!)


It's important to realize that even a meteor passing directly overhead is
likely tens of miles away and the delay in hearing it directly would be at
least a few _minutes_ to several minutes.  I think it is generally accepted
that meteors can be "heard" while they are visible, but only because the
electromagnetic impulses they generate can cause nearby rocks and other
materials to vibrate or discharge, etc.  A web search will show several
explanations which give further details, such as at
http://www.ticetboo.demon.co.uk/audible.htm .

I have never heard any noise from a meteor myself (even having seen dozens
of fireballs/bolides brighter than -5 or so, and one daylight bolide), but
I believe I have seen the effect of an EM pulse from a meteor.  I spent a
couple of nights observing at Kitt Peak in September 1982 and at one point
the ground lit up like day and a very bright bolide flashed across the
northern sky (I was facing south of course so only saw the long lasting
train).  At that moment all the power on the mountain failed and the main
noise we began to hear was several emergency generators kicking in.  No
proven connection here, but an unlikely coincidence in my opinion.

- Brent Archinal



                                                                                
                                    
                    Wil Milan                                                   
                                    
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                    az-observing-bounce@fre        Subject:     [AZ-Observing] 
Re: BOLIDE! (photo!)                 
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                    11/21/01 07:05 PM                                           
                                    
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At 05:49 PM 11/21/2001, you wrote:

>What is the 'contemporary' definition of a bolide?  The definition I
>have is:
>"A fireball accompanied by one or more audible explosions, often
>associated with meteorite falls...Many shock waves may be set up if
>considerable fragmentation occurs, causing a rumbling noise which
>follows the first major fragmentation"
>
>This definition does not say anything about color.  So far no one has
>said they heard an explosion (or did I just miss it? - someone said they
>heard some sputtering).  Is this object really a bolide?  Is one or more
>explosions assumed to exist even when not heard if it looks and feels
>like a bolide to experienced observers?  Since it was near polaris, my
>guess is that it was somewhere between 30-90 miles from the observer (in
>a straight line), and so maybe it would not be possible to hear an
>explosion.

The photo shows what look like a number of outbursts or explosions along
the burn path, and I presume if one were close enough one would have heard
the explosions.


Wil Milan
...



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