Saturday, 23 April 2011

Have you ever noticed . . . condescension?

Whenever the windows in a car get steamed up, a good old friend of mine (with a wry smile) complains about the 'condescension'!  He knows exactly what he is doing and often gets a laugh.  So - does that make the following picture a 'condescension trail'?



Now, forgetting all the conspiracy theories about 'chem trails', I wonder whether you have ever noticed something interesting about the way the trails are not symmetrical.  This photo of the trail from a four-engined aircraft is typical and it illustrates my point.

Did you notice how the condensation trails from the engines on the right wing combine almost immediately, whereas the left wing remains as two distinct trails for some time.  Next time you look up into the sky on a sunny day, you might be able to see it for yourself.  You will need to spot a four-engined plane - but they are not very rare (unless you live in an area with no major trans-continental flight paths overhead).

I have a view about the reason for this.  Do you?  Feel free to comment and start a discussion.

This second photo came to my attention recently too.



Beautiful!  And there is some fantastic physics at work in between the trails, and perhaps some clues about what is going on in the first photo.

9 comments:

Pruthvi said...

Is it because the aircraft is turning to the right or left ?

Plasma Engineer said...

That's a good suggestion, but not the one that I was thinking of. My own view is that the second photo gives a good clue. You can see the way that the vortices from the wings make the trial from the outer engines curve over those of the inner engines. Depending on the position of the observer, the trials from one wing are likely to appear separate while those from the other wing appear to have combined. If this is true it is merely an effect of the perspective rather than a true combination. I retain an open mind though.

Pruthvi said...
This comment has been removed by the author.
mighquis said...

I agree was Plasma Engineer's synopsis of the perspective theory. If you closely examine the first image you can say that it is taken from an angle.

Fil Salustri said...

I've seen lots of engine contrails that maintained all 4 steams nicely. I suspect what you're seeing, if not perspective, is the result of an asymmetry caused by a crosswind or solar or friction heating of the engine cowling.

Plasma Engineer said...

There is another hypothesis, that on one side the vortex from the end of the wing is in the same direction as the rotation of the exhaust from the engines. On the other wing they counteract. I used to favour this explanation until I saw the second of the photos above. I'd be fascinated to see a photo of one where neither wing's trails combine early.

Anonymous said...

nothing 'beautiful' about this Crime Against Humanity...total TRAVESTY....WAKE UP & LOOK UP

Plasma Engineer said...

Crime against humanity is it? I would understand if you claimed it to be a crime against ecology.

Ross Marsden said...

... or a crime against the aesthetic appreciation of a natural sky.