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# Jet Contrail Problem

Sat 30 May, 2015 03:20 am
Hi All - I wonder of anyone can explain this:

I was sitting on a bench looking into the sky when I noticed a jet and its contrail (probably several miles away). The line marked by the contrail and jet was perfectly perpendicular to the ground and was observed through a gap between the edge of a building (on the left) and some tall trees (on the right). The gap is about 10m wide and I am sitting about 30m away from it. Think of the building edge, the treeline and me as an inverted isosceles triangle, with me as the apex.

The line marked by the jet and its contrail is parallel to the vertical edge of the building and visually close to the left edge of the gap between the building and the trees. Based on the straight line, the jet appeared to be heading in my direction.

The sky was clear with a few clouds and a light wind and the clouds were moving left to right with the wind.

But here's what I don't get. The line marked by the jet and its contrail was also moving left to right, at the same speed as the clouds, whilst always remaining perpendicular to the ground and parallel with the side of the building. Within about 20 seconds it had moved all the way from the side of the building to the trees. So, although I could see the jet and the contrail as distinct objects, effectively, it looked like a vertical line moving from left to right.

I am assuming that the wind could not blow a jet sideways at that rate and would, therefore, have expected to see a variation in the line of the contrail if it was being blown and the jet was not. (i.e. the parts of the contrail furthest from the jet would be blown more to the right).

I have a photograph of the gap from my perspective but, unfortunately, there is no facility to upload it, so I hope my explanation makes sense.

None of my physics colleagues can explain it, so I wonder if anyone here can?

Regards

Terry

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jespah

1
Sat 30 May, 2015 03:53 am
@Terryfc,
Go to Photobucket or Image Shack or Imgur and upload your photo, and post the links here.
Terryfc

1
Sat 30 May, 2015 06:09 am
@jespah,
Hi Jespah

Here is the Photobucket link. The background is the actual place - the jet and contrail image I added on Photoshop, showing the initial contrail/jet (Position 1) and where it was about 20 seconds later (Position 2).

Hope this helps

Regards

Terry
Butrflynet

1
Sat 30 May, 2015 01:58 pm
@Terryfc,
For those who don't like to click.

roger

1
Sat 30 May, 2015 03:03 pm
@Butrflynet,
Thanks. While I have no explanation for the change in position, approaching aircraft as a stable altitude often look like they are climbing. Maybe there's a clue there for someone else.
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