[meteorite-list] Images of UK contrail (not fireball)

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:21 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4EDC8_at_US-Torrance.mail.saic.com>

Hi All,

My turn to chime in on the Wales photos. First of all, it's great
that it's now photos PLURAL, since this rules out Photoshop mischief,
and it allows some degree of triangulation which can be used to
approximate altitude.

I'm leaning toward backlit aircraft contrail for three reasons --
the first of which has been mentioned, but the other two have not:

1. No sonic boom. If this was a bolide, it should have produced
a whopper! Not a single report of a sonic boom.

2. Where are all the observers? This occurred near sunset -- an
optimum time for people to be outdoors in (evidently) nice weather.
If you think the contrail is impressive, consider what the brightness
of the bolide should have been to produce it -- we're talking at
least magnitude -20, probably considerably brighter. People don't
miss fast-moving second suns. How is it that witnesses would be
attentive enough to spot the contrail, yet inexplicably miss the
far more spectacular bolide that produced it just seconds or minutes
before?

3. Perhaps the best evidence is the nature of the contrail itself.
Because a bolide has a downward component, any contrail it produces
will also. Differential velocities of upper atmospheric winds versus
altitude will cause the contrail to corkscrew and scramble fairly
rapidly, much like the contrails we see from Vandenberg rocket
launches on the west coast. In contrast, jet contrails are at
relatively constant altitude, so while they, too, get blown by the
wind, all portions of the contrail are exposed to roughly the same
wind direction and velocity. The result is that jet contrails
keep their shape longer, merely getting "fuzzier" with time. The
minutes-later image of the Wales contrail doesn't show any evidence
of kinking/corkscrewing, and that perhaps is the strongest evidence
against it being of space origin.

Best,
Rob
Received on Fri 03 Oct 2003 03:30:14 PM PDT