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Location: UFOUpDatesList.Com > 2007 > Jan > Jan 3

Re: The '06 O'Hare UFO - Tarbell

From: Michael Tarbell <mtarbell.nul>
Date: Wed, 03 Jan 2007 14:25:11 -0700
Fwd Date: Wed, 03 Jan 2007 16:54:46 -0500
Subject: Re: The '06 O'Hare UFO - Tarbell

>From: Martin Shough <parcellular.nul>
>To: <ufoupdates.nul>
>Date: Wed, 3 Jan 2007 16:31:53 -0000
>Subject: Re: The '06 O'Hare UFO

>>From: Michael Tarbell <mtarbell.nul>
>>To: ufoupdates.nul
>>Date: Tue, 02 Jan 2007 10:39:55 -0700
>>Subject: Re: In the sky! A bird? A plane? A... UFO?

>>>From: Martin Shough <parcellular.nul>
>>>To: <ufoupdates.nul>
>>>Date: Mon, 1 Jan 2007 15:35:15 -0000
>>>Subject: Re: In the sky! A bird? A plane? A... UFO?


>>(1) the water droplets in the cloud were heated to the vapor
>>state; or,

>>(2) the size distribution of the droplets was modified such
>>that they no longer were effective scatterers at visible

>>For case #1 it should be possible to put constraints on the
>>radiative power of the object based on the size of the "hole".
>>It seems that a black body radiator would have to be extremely
>>hot to produce such an effect, to the extent that it would glow
>>in visible wavelengths (at odds with the dark grey color
>>ascribed to it). But perhaps it radiated at a specific
>>wavelength (e.g., microwaves).

>>For case #2, the most straightforward scenario is that the
>>droplets coalesced into larger ones and rained out, but the
>>mechanism to bring this about is not obvious. Perhaps some
>>local stratification of electric charge?


>It's a good point though that _if_ we had reliable data on a
>volume of cloud evaporated then it might be possible to do this
>calculation. I recall there was case, I believe in the northern
>US or Canada in 1947, where a bolide-like UFO was photographed
>apparently cutting a swathe through cloud and Projectr Sign
>noted the possibility of doing a similar calculation (though
>I've always wondered in that case whether the apparent path
>through the cloud might not be shadow cast by a trail far above,
>having seen similar effects caused by high jet contrails). But
>anyway it's interesting.

An obviously critical parameter is the "excavated" volume of
cloud. I have emailed Peter Davenport off-list to see if has is
aware of any data regarding the thickness of the cloud layer, as
well as the angular width of the hole.

>As for how a "hole" might form, yes a narrow band emission in a
>mm/cm range optimised for absorption by water droplets seems
>more likely than a broad spectrum one. If not evaporation then
>charge separation is one means, as you suggest. Mechanical
>and/or thermal displacement of the air could also be factor.

A selective emission in the microwave regime would certainly
reduce the power requirements. I am not particularly enamored of
this radiative mechanism regardless of the bandwidth, but the
calculation is still worthwhile.

I also considered the mechanical displacement mechanism (via
entrainment of unsaturated air behind the object) but several
things about it are troublesome. If this were a viable
mechanism, I should think it would be observed more often with
conventional aircraft. I further think that the effect would be
confined to perhaps ~several object diameters, while the witness
accounts give the impression that it is more substantial than
that (pending additional info from Peter and/or others).
Finally, I would expect such a hole to "fill in" fairly quickly
as the entrained air cools below the dew point. Hopefully
someone with experience in atmospheric physics will comment.

Perhaps another mechanism to consider is the interaction of a
bow shock with the water droplets. But here again, this should
be observed routinely with supersonic aircraft. I do know that
isolated droplets in general are fairly stable against the
passage of a shock front. Apparently no sonic boom was heard,
but none would be expected if the object was traveling straight



>The approach end of Runway 32 Right is in a direction roughly NE
>from the Tower shown on the FAA map. Presumably cold weather is
>very possible in November in Chicago. If so then the steam plume
>could have restricted tower visibility to the NE. Whether this
>has any relevance to the position of the UFO I've no idea but
>it's worth bearing in mind.

>The remote possibility that a "hole" in low cloud could be
>related to some 'belch' in the exhaust plume from a
>malfunctioning airport heating plant has occurred to me, but I
>don't think it very likely!

I wouldn't disregard this so quickly, unless further witness
information makes it completely clear that the appearance of the
hole is unambiguously tied in both time and position to the
upward motion of the object. The accounts thus far certainly
give that impression.


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