Chemtrails are a conspiracy theory-level line of confused thinking, usually with a lack of a full understanding of the science behind aviation, that says that the high altitude lines of clouds produced from commercial airliners are in fact chemical sprays – from the government – that are designed to produce a number of effects (such as population control or other evil government-engineered schemes).
In all actuality, chemtrails don’t exist, and never have. The correct term is contrail – Condensation Trail. When an aircraft flies at a certain altitude, in a certain manner, and under certain weather conditions, a stream of artificially created clouds do indeed form behind it. As a holder of a PPL (Private Pilot License) since I was the age of 16 I learned all about these kinds of aviation-related phenomena, and it never occurred to me that many people thought they were some sort of evil conspiracy until many years later.
The main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapour emerges into a cold environment, and the local increase in water vapour can raise the relative humidity of the air past saturation point. The vapour then condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails. The time taken for the vapour to cool enough to condense accounts for the contrail forming some way behind the aircraft’s engines. At high altitudes, supercooled water vapour requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft’s exhaust act as this trigger, causing the trapped vapour to rapidly condense. Exhaust contrails usually occur above 8,000 m (26,000 ft), and only if the temperature there is below −40 °C (−40 °F). (For more information on this consult this FAQ over at NASA.)
Contrails are only formed in a long-term manner if the above conditions are met (and since weather conditions exist in near-infinite combinations at all altitudes of the sky, a large variety of contrails can be observed in a single day).
Contrails form from either the engine exhausts, the wing tips, or even the wings of the craft itself. This can produce pencil-thin contrails, fat blanket-like ones, or even a stream of 4 lines (one from the 4 on-board engines). They can last as long as a few seconds, or across the length of an entire day.
Some of the more common misconceptions about contrails, and how the argument that they are actually a chemical spray trail include:
“Contrails used to vanish from the sky always in just a few minutes, or less”. — This line of thinking is based on a lack of actual facts, and relies on personal memory (which is NOT accurate in the least). It should be noted that for every person who says that they used to vanish quickly, there are just as many people who remember them staying in the sky for hours upon hours (which is why debates involving personal memories are not good).
Truth be told, there is huge droves of evidence that shows that contrails have been pretty much known about, and documented, as far back as the 1920s. The first documented instance of a contrail is a passing mention attributed to a man named Ettenreich, who in 1919 reported an incident from 1915 where he saw “the condensation of a cumulus stripe from the exhaust gases of an aircraft”
There is even an old article called “Clouds formed by Airplanes“, in the June 7th, 1919 issue of Scientific American (page 60).
Even less known is that, under precise conditions, a herd (or even a single) of animals can produce a contrail right behind them as they run – the released water vapor from the ground beneath their hooves contacts the temperature differences in the air and forms one, to rather striking effect.
You can even see streams of contrails appearing in old WWII movies – the bombers flying overhead have them streaming out behind them (again, proper conditions permitting).
So: No, contrails are not a new thing.
I’ve seen photos and/or videos showing planes spraying stuff. — Every photo and/or video I’ve ever seen of these supposed chemtrail-spraying planes is either faked, misunderstood, or wildly inaccurate.
One of the most popular that is whizzing about the internet lately is this one, which has a faked warning (somebody added it via a photo-manipulation program) in the background that seems to say something about a Hazmat suit being required. The original photo can easily be found here at this website.
This is the interior of a Boeing 777-200LR Worldliner, a plane that was used for flight testing. The barrels contain simple tap water, which is pumped around to shift the center of gravity to test various flight characteristics.
What sort of testing? Well, they are going to be carrying a load of passengers on this craft, right? They sure as hell are going to do every test possible to make sure that the craft is fully understood and safe before they put real people on it.
The water is used to find out exactly how the craft performs as heavy fuel loads are shifted around, what different configurations and loads of passengers will do, what flight maneuvers will do, and lots more.
This aircraft has all kinds of tubes, pipes, and air ducts mounted on it, facing every which way, and the aircraft itself is the only one that I know of configured like this. In actuality this plane is used to sample the atmosphere. It’s a research aircraft, registration N701BN, operated by the Department of Energy’s national labs. In fact you can read an article about it over at this DoE website.
For example, in the photo to the right, which is of an E6B “Tacamo” (a modified version of the Boeing 707-320) which has had its fuel vents moved from the wing tips to between the fuselage and the engines in order to separate it from the communication equipment in the wing tips. Why in the world would an aircraft intentionally dump precious fuel into the sky? Well, fuel weighs a lot, and when it comes time to make a landing the landing gear (as well as the craft itself) can only support so much weigh (especially at that small point of impact when the wheels smack into the runway), so if the craft is over the max allowed landing weight fuel is vented right out of the craft until the weight is within safety limits.
As you can see from the previous examples, all instances of chemtrail theories start with a misunderstanding of the aviation industry.