A Rainbow Aerodynamic Contrail

[Mick West]

via email from Ron Smith

In the UK. I live in Henstridge, Somerset, UK and the
aircraft was about 1 mile south of me, tracking east west.
Taken 18 July 2015
~1300 local showing a BA Boeing 777-300. It was just beginning to pass
above a cloud layer when the aerodynamic pressure field around the
aircraft produced this delightful contrail.

Content from external source

 

[Spectrar Ghost]

Very nice!

 

[Henk001]

Wondering when this will pop up in the blogosphere, claiming it can't be natural

 

[Mick West]

Added location to the OP

 

[skephu]

Must have been this:

 

[Mick West]

Interesting that again this show the difficulty of estimating how far away a contrail is from you. Ron (an experienced pilot and aviation expert) thought it was "about 1 mile south", when it was actually 4.5 miles at the closest point.

 

[Efftup]

Yeah, I had a similar situation earlier. I saw a contrail ALMOST overhead (within 10 miles then ) that just LOOKED Really low. Just something about it made me think it looked no more than 5-10,000ft, despite the fact that I had no other terms of reference.

 

[Mick West]

99% of the visible sky is over 10 miles away

 

[Spectrar Ghost]

Clarification: at 30k ft?

 

[Mick West]

Clarification: at 30k ft?

Yes, the comment is intended for roughly that altitude. 99% a good ballpark figure given that you can usually quite easily see contrails (and clouds) over 100 miles away. So the area of a 10 mile radius circle (100 square mile) is just 1% the area of a 100 mile radius circle (10,000 square miles).

The actual amount varies with exactly how you measure it. For example, you can actually see around 200 miles if you are looking at things at typical contrail altitude, so you could say that 99.9975% of the sky is over 10 miles away. However it's quite hard to see things over 100 miles. I commonly see planes leaving contrails off the coast of San Francisco, those are about 115 miles away.

Perhaps a better way of putting it would be "Over 99% of contrails that you see are over 10 miles away"