Contrails form when the water vapor in hot exhaust gasses mixes with the freezing cold exterior air. As it cools, the relative humidity is raised enough that a cloud is formed.
Since it takes a little while to mix enough for this to happen, there's a gap between the engines and the start of the contrail. There are many great closeups of this on various contrail spotting web sites.^
The relative size of the gap varies quite a bit ^depending on the size of the plane, its speed, and the ambient conditions. On a two engine plane (especially mid-sized jets like the A320 and B737) it is not uncommon to see the contrails start about at the tail of the plane. Notice how they are exactly lined up with the engines.
But they can also start quite a bit behind the tail^, again still lined up with the engines.
Or inside the tail^:
Unfortunately some proponents of the "Chemtrail" theory use low resolution photos or video of trails starting near the engine, and they suggest it is actually being sprayed from the tail. For example:
http://www.geoengineeringwatch.org/chemtrails-spraying-from-the-tails/ (http://archive.today/yM4GI)
With the following video:
Now it's quite clear from looking at the video in the context of the above photos that it's simply a two engined plane with the contrails starting approximately at the tail. The resolution of the video is too low to make out exactly where it starts. However it's quite consistent with many high resolution photos of similar planes, where the trail is clearly coming from the engine. Here I've collected images of similar planes leaving a range of contrails. The plane from the video is at the bottom middle. The most similar plane is in the center.
https://www.google.com/search?q=delta site:www.luchtzak.be&es_sm=119&source=lnms&tbm=isch^
So there's nothing yet to suggest it's not just a contrail. But the maker of the video goes on to produce what he claims are "infrared" images that "prove" that the trail starts at the tail.
Consider for a second what is being claimed here - there's some super hot trail being emitted from the tail, and yet the jet engines, which have an exhaust temperature of up to 900°C (but typically 650°C at cruise), are not showing up at all? It is clear whatever this image is, it is not an infrared (heat) image.
An actual thermal image of a jet looks like:
Source: http://proof.nationalgeographic.com/2014/03/03/tyrone-turner-thermal-imaging/ (http://archive.today/QIrzC)
This shows the very hot exhaust cooling down very rapidly, so that by the time it reaches the tail, it's close to ambient air temperature.
In fact the image in the video is just a simple photoshop adjustment, known as a gradient map. This takes the brightness of each point in the image, and converts it to a color on a predefined color gradient or spectrum.
It's just a few mouse clicks, and many simpler programs might include similar functions as a novelty effect.
So all this is doing is showing you which bits of the image are brightest. It's purely a function of visible light (i.e. what you can see in the photo), and nothing to do with heat. We can apply it to any image:
Conclusion: It's just video of normal engine exhaust contrails that just happen to start near the tail, and some fake "infrared" images.
Since it takes a little while to mix enough for this to happen, there's a gap between the engines and the start of the contrail. There are many great closeups of this on various contrail spotting web sites.^
The relative size of the gap varies quite a bit ^depending on the size of the plane, its speed, and the ambient conditions. On a two engine plane (especially mid-sized jets like the A320 and B737) it is not uncommon to see the contrails start about at the tail of the plane. Notice how they are exactly lined up with the engines.
But they can also start quite a bit behind the tail^, again still lined up with the engines.
Or inside the tail^:
Unfortunately some proponents of the "Chemtrail" theory use low resolution photos or video of trails starting near the engine, and they suggest it is actually being sprayed from the tail. For example:
http://www.geoengineeringwatch.org/chemtrails-spraying-from-the-tails/ (http://archive.today/yM4GI)
With the following video:
Now it's quite clear from looking at the video in the context of the above photos that it's simply a two engined plane with the contrails starting approximately at the tail. The resolution of the video is too low to make out exactly where it starts. However it's quite consistent with many high resolution photos of similar planes, where the trail is clearly coming from the engine. Here I've collected images of similar planes leaving a range of contrails. The plane from the video is at the bottom middle. The most similar plane is in the center.
https://www.google.com/search?q=delta site:www.luchtzak.be&es_sm=119&source=lnms&tbm=isch^
So there's nothing yet to suggest it's not just a contrail. But the maker of the video goes on to produce what he claims are "infrared" images that "prove" that the trail starts at the tail.
Consider for a second what is being claimed here - there's some super hot trail being emitted from the tail, and yet the jet engines, which have an exhaust temperature of up to 900°C (but typically 650°C at cruise), are not showing up at all? It is clear whatever this image is, it is not an infrared (heat) image.
An actual thermal image of a jet looks like:
Source: http://proof.nationalgeographic.com/2014/03/03/tyrone-turner-thermal-imaging/ (http://archive.today/QIrzC)
This shows the very hot exhaust cooling down very rapidly, so that by the time it reaches the tail, it's close to ambient air temperature.
In fact the image in the video is just a simple photoshop adjustment, known as a gradient map. This takes the brightness of each point in the image, and converts it to a color on a predefined color gradient or spectrum.
It's just a few mouse clicks, and many simpler programs might include similar functions as a novelty effect.
So all this is doing is showing you which bits of the image are brightest. It's purely a function of visible light (i.e. what you can see in the photo), and nothing to do with heat. We can apply it to any image:
Conclusion: It's just video of normal engine exhaust contrails that just happen to start near the tail, and some fake "infrared" images.
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