Someone recently made me aware of this apparently somewhat popular conspiracy theory which says that contrails (the white lines behind large airplanes) are basically crop-dusting the country with chemicals. I can see how someone could think this, I’ve looked at a contrail and thought “man that plane must give off a lot of exhaust”, and it wasn’t until I looked into it that I discovered that the trail behind a plane isn’t the exhaust, because the exhaust is invisible since the fuel is kerosine which like car exhaust gives off invisible carbon dioxide/monoxide emissions as a byproduct. This is why you don’t see billows of smoke when a jet is warming up on the runway or taking off, though you may see wavy lines from the heat. No, the contrail is actually a long, artificial cloud created by the air flow of the plane condensing the moisture in the air, then the engines heating it and it rapidly cooling in the wake of the plane and crystallizing to form a cloud. And while it undoubtedly does contain some exhaust from the plane, it is almost entirely composed of water from the air.
The conspiracy theory goes on to say that short contrails are contrails, and long ones are so-called chemtrails, or chemical trails. In other words, this is a contrail:
While this is supposedly a chemtrail:
Note that the “chemtrail” does not start at the back of the plane as it would if it were something coming out of the plane, but rather it starts a significant distance behind it (due to the water vapor taking a little time to cool down and become visible). Whereas crop-dusting looks like this:
No gap between the chemicals and the dusting apparatus.
The length of the contrail is also heavily effected by the temperature of the surrounding air, the speed of the plane and the level of humidity. In dry, hot climates or at lower altitudes the contrail will be shorter since the water vapor will dissipate or evaporate quickly, while in other climates or at higher altitude (where it is typically much colder) contrails can stretch for miles.
According to the conspiracy theories “chemtrails” are everything from toxic chemicals meant to kill us to atmosphere modification to fight global warming. There is no evidence for these “chemtrails” I have yet seen, it is generally people speculating from their backyards as far as I can tell. One video has a guy who collected rain water that fell while planes were flying overhead and said he had it analyzed, then listed all the daangerous and scaaary things found in it, like arsenic and aluminum etc. But these are extremely common in nature and are found in trace amounts in almost anything – no element is harmful in a small enough amount, you need a certain concentration to be hurt by something. But people without chemistry backgrounds who don’t know this stuff is everywhere think it must have come from airplanes.
These conspiracy theorists never seem to ask themselves questions like “why would someone who presumably needs to breathe air just like everyone else want to poison the atmosphere?” or “if someone wanted to fight global warming by reconfiguring the planet why wouldn’t they just put up solar reflectors in the desert or something?” Or “how could any airline stay afloat financially when they’re procuring and dumping billions of tons of crap into the atmosphere?” Or “how could this be feasible since every airline in the world would have to be in on it (since they all have planes that produce long contrails) and we’d have heard about it from a whistleblower decades ago”, etc.
But then I’m sure that’s where the CIA or the greys or the illuminati come in…
See also: RE: The Fluorine Conspiracy Theories.