Last Monday was the three year anniversary of the iconic video of that insane lady in Utah spraying her backyard with vinegar to rid the sky of "chemtrails" and making her son videotape the occasion as proof for the internet. The lady truly believes that spraying vinegar at the sky will magically ascend 35,000 feet to dissipate some clouds she doesn't like.
The whole business of "chemtrails" is a bunch of hokum perpetuated by people too lazy to understand real science, so they make up their own truth to make themselves feel smart. Chemtrails do not exist. The real phenomenon is called a contrail, short for condensation trails. Contrails form when hot, moist jet exhaust meets incredibly cold upper-atmospheric air and condenses almost immediately into a long, narrow cirrus cloud. The contrails stick around for a few minutes or a few hours depending on atmospheric conditions.
Contrails are completely harmless. They're just condensed water vapor. The idea that there's a vast conspiracy to spray everyone with chemicals to make us sick, control our minds, or make us grow a third nipple is as much silly as it is scientifically unjustifiable.
One of their most popular comebacks is to ask why contrails don't form on the ground when it's cold out. They do, actually. In incredibly cold areas of the planet (like northern Canada and the South Pole), departing and landing aircraft can leave contrails at ground level if the air temperature is cold enough.
Another popular trope among chemtrail conspiracy folks is to circulate pictures of center-of-gravity ballasts in test aircraft as definitive proof of chemtrails, which is also wrong. Besides, if every aircraft had these tanks full of ChemJuice, the passengers would have nowhere to sit. That brings us to the next point — where would the planes keep all of these nefarious chemicals, anyway?
I wrote a piece for the Washington Post's Capital Weather Gang last summer about weather control conspiracy theories (including the chemtrail conspiracy), wherein I used the example of a Boeing 747 to show that the weight of the chemicals alone would pose an issue to the aircraft:
Liquids are heavy. One gallon of jet fuel weighs approximately 6.7 pounds. Take a Boeing 747-400, for example: a fully-loaded 747 flying from London to Hong Kong would require almost a full tank of gas – somewhere between 50,000 and 60,000 gallons of fuel. That's upwards of 370,000 pounds of fuel in the tanks. Between the weight of the fuel, the passengers, the cargo, and the luggage onboard, there's simply no room left for "chemtrail" chemicals even if they did want to spray us all with toxic gunk.
The tin-foilers refuted that right off the bat, of course. They directed me to their Facebook pages and skeevy forums where they discuss how the United States Government is out to get them for good this time. The system they've set up online is actually pretty interesting; a self-referential circlejerk, if you will. Person A writes a completely baseless article "confirming" all of their fears and suspicions. Person B cites Person A as proof. Person C cites person B. Then Person A turns around and says "see! Person C said it too! I'm not crazy!" It's a self-perpetuating cycle of anti-science.
It's incredible to see how many people buy into the conspiracy theory. A couple of months ago, I took an incredible picture over Mobile, Alabama that I shared to the Capital Weather Gang's Facebook wall. Almost instantly, hundreds of chemtrail weirdos swarmed the picture calling me every name in the book for calling it "beautiful" and having the gall to refute their claims.
The picture shows a distrail — short for dissipation trail — caused by an airplane flying through an existing deck of clouds. Its jet exhaust caused the supercooled water droplets in the cloud to condense and precipitate, leaving a cut through the middle of the clouds.
In the middle of the distrail was another cool meteorological phenomenon known as a sun dog, which often appears as a small rainbow-colored feature that can show up in clouds dense in ice crystals when the sun is at the right angle. It was one of the most impressive skies I've ever witnessed, and it's completely explainable using science.
Unfortunately, most of the people who subscribe to the chemtrail conspiracy theory won't respond to science no matter how much you try to explain it to them. Sometimes, as with the video, all you can do is point and laugh.