Eugene writes:
> Apparently it's an RF effect, and hence almost instant.
The original post from JR pointed to
http://science.nasa.gov/headlines/y2001/ast26nov_1.htm?list76937
which had some explanation of the theory.
I'm not sure I buy it completely though, for several reasons.
First, as I understand it the theory only works for very large meteors.
Only those are such that there would be sufficient energy produced in
the trail to generate enough EM radiation that it could vibrate natural
objects 50 miles away, loud enough for people to hear. Not having
read the literature I'm astonished that this would be possible at all,
but from reading the web pages it sounds like this is the most favored
theory. They claim that such large meteors could generate megawatts of
EM radiation.
However I think people sometimes have reported the effect even for
relatively small meteors like the bulk of the Leonids we saw the other
night. These are the size of grains of sand and there is no way they
could radiate enough EM to be heard through a random natural object, IMO.
Second, I can't find any references on the web but I remember reading
years ago another theory, which was that this was a psychoacoustic effect
related to synesthesia, which is a crossover of sensory modalities. You
see a light and under some circumstances you can hear a sound. Meteors
are extremely eerie, so sudden, so fast, and so silent. We are accustomed
to hearing noises associated with streaks of light, and so there is an
inherent expectation that meteors ought to make noise. This can cause the
illusion of noise in some people.
I seem to recall reading experiments in darkened rooms where streaks of
light are projected on the ceiling to imitate meteors, and some people
reported sounds.
Third, why are there no recordings of these meteor sounds? The Leonids
for the last couple of years (and next year as well) would be excellent
candidates. Build some antennas that ought to turn these waves into
sound, and put a microphone next to them. That would go a long way
towards proving the theory. AFAIK this has not been done, which makes
me skeptical. (Note, there are web pages with "meteor sounds", but
these are electronically detected; I mean an acoustic recording.)
Hal
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