(meteorobs) Why do some meteors appear to zig-zag? Wavering sounds
E. L. Jones
jonee at epix.net
Thu Jul 8 19:57:43 EDT 2004
Hello Lew, Gang.
I understand well the tendancy for the human mind to fill in the blanks
when it comes to recalling fast paced phenomena. I'd like to believe
that I am a bit more experienced observer than the average fireball
reporter and I try to accurately sense fast moving situations. I have
heard a sequence of sounds from a meteor that didn't include a sonic
boom, a bolide burst, nor electrophonic sounds.
April 23, 2000 around 3:10 in the afternoon I was in my yard here in
the Poconos of Pennsylvania and heard the transit of what I believe to
be a fast moving meteoroid. I say "heard" because I didn't see it.
Owing to the fast transit and apparent 25-35° down angle , I excluded
an aircraft(no engine sound), rifle bullet (trajectory wasn't flat
enough) or a part falling from an aircraft (trajectory was too fast and
not vertical enough) . The object produced a whoosh sound constantly
but had an embedded whap.......whap,whap....whap.......whap,whap sound.
I presumed this to be a tumbling object with three prominences which
changed pitch as it tumbled in the slipstream.
As to potential mechanisms, one which is not likely at play this time
here is the advance and retreat of a helicopter blade tip can break the
sound barrier on the forward motion while falling below that threshold
on the rearward movement. The result is a series of sharp cracks when
the conditions are right. I could imagine a meteoriod in dark flight
while still supersonic to produce different shock waves if it were tumbling.
I think the category of sound I heard is due to tumbling at high speed.
A tumbling artillery or mortar canister--after releasing a parachute
flare, will produce a similar wavering pitch. Shrapnel will also produce
a distinctive sound. Large caliber aircraft cannon cases have a
distinctive sound differing from smaller cases. In parachute training
at Ft Benning, the instructors used to guess what was falling from basic
parachute trainees as they exited the aircraft and lost equipment from
their packs. Each category of object, coin, ripcord handle, helmet,
camera whatever, have different sound signatures. Most everything
produces a constant whoosh sound. Anything may produce a series of
sounds if they are tumbling relatively fast against an airflow(
turbulent vs laminar flow). Objects down to a foot long or so can be
heard kilometers from where they are falling. I believe the ultimately
we will find that the subsonic (and perhaps supersonic) sounds vary with
the cross section facing the windward side, peaks and hollows on the surface
So, after what I have seen--I mean "heard" happen, and taken with other
reports by close witnesses who reported a whoosh as a meteoroid passed
near by, I believe that meteoroids can and do produce subsonic wavering
sounds. I believe this is technically due to rapidly changing cross
sectional aspect in the slipstream or in lay terms-- tumbling cartwheels
Now after all this showing off I've done as I reread your post, is it
only simultaneous sounds wavering that your comment was about? Arrrghhh
In that case it still could be due to tumbling if the tumbling changes
the output of the plasma envelope by deflecting it or uping the output
as more cross section is stuck out into the stream. If the
electrophinics are induced by Radio Frequency (RF) waves chances could
be that the tumbling is acting on the RF emissions much like tunning an
>Date: Wed, 7 Jul 2004 17:55:32 -0400
>From: "Lewis J. Gramer" <lgramer at upstream.net>
>Subject: Re: (meteorobs) Why do some meteors appear to zig-zag?
>BTW, MexicoDoug, I also found your post interesting - although it does raise
>questions in my mind at a couple of points. For one, I noticed that the reports
>you cite mention "sounds" heard during the fireballs witnessed: though there
>is good evidence now that simultaneous or "electronphonic" sounds are in fact
>real observable phenomena, I have never heard any potential mechanism for
>these sounds, which would allow a rotating meteoroid to result in "wavering"
>or otherwise changing sound heard simultaneously on the ground... Does anyone
>else have any information on this particular point?
>In fact, if anything, the fact that these sounds are mentioned in the reports
>cited, might SEEM to indicate that the reporting observers were either:
> a) reporting something much closer to them than a meteor, e.g., fireworks;
> b) very "suggestible", in their recollections of what they observed.
>In any case, thanks to all who have posted so far on this thread: during the
>times between major showers, it's always interesting to bring up these old
>chestnuts from past years' debate on 'meteorobs'. :)
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