Photo: Some conspiracy theorists believe that contrails formed by jet exhaust are part of a secret government plot to alter the atmosphere. Credit: Mick West/UCI

If you're fascinated with conspiracy theories, you've probably come across one involving those streaks that jet aircraft leave behind them in the sky, as particles from the engines' exhaust plume cause water vapor in the air to condense around them and form ice particles. In aviation, those streaks are called "contrails," short for condensation trails, and they're a phenomenon that's been observed since the beginnings of jet-powered flight. (Here's a Federal Aviation Administration FAQ on them.)

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Nevertheless, to conspiracy buffs, nothing is that simple or innocuous. Some believe that the streaks are what they call "chemtrails," and that they're part of a sinister, clandestine government plot to modify the weather, or else some sort of biological warfare weapon. (From the Committee for Skeptical Inquiry, here's a guide to those accusations.) One poll a few years back found that nearly 17 percent of Americans thought it was either true or partly true that the government was involved in atmospheric alteration, and the chemtrails conspiracy theory even has been promoted by celebrities such as Kylie Jenner and the late Prince.

That's why a group of scientists from the University of California, Irvine, the Carnegie Institution for Science and the nonprofit Near Zero organization thought it would be a good idea to survey 77 atmospheric chemists and geoscientists, the folks who actually study the atmosphere. The survey-takers asked atmospheric researchers if they had found any evidence of a large-scale program to spray chemicals into the sky.

An article just published in Environmental Research Letters contains the findings. Of the 77 scientists surveyed, 76 (98.7 percent) said they had found no evidence of such spraying.

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Beyond that, when showed the evidence presented by chemtrails proponents -- such as strontium, barium and aluminum found in water, soil and snow samples -- the researchers concluded that those things could be explained through other factors, "including well-understood physics and chemistry associated with aircraft contrails and atmospheric aerosols."

If you're a believer in chemtrails, you may be wondering: What about the one scientist who found evidence? Maybe that person is the InfoWars version of Galileo, right?

Sorry to disappoint you, but no.

As the study clarifies: "The one participant who answered yes said the evidence s/he had come across was 'high levels of atmospheric barium in a remote area with standard 'low' soil barium'." That scientist stops short of absolutely ruling out the remote possibility that someone deliberately sprayed barium over that area, which is not the same as saying that it's the likely explanation. (As Bad Astronomy blogger Phil Plait explains, "When I can't find my keys in the morning I can't rule out that dinosaur ghosts hid them from me. It just seems a tad unlikely.")

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"The chemtrails conspiracy theory maps pretty closely to the origin and growth of the internet, where you can still find a number of websites that promote this particular brand of pseudoscience," study co-author Steven Davis, UCI associate professor of Earth system science, said in a UCI press release. "Our survey found little agreement in the scientific community with claims that the government, the military, airlines and others are colluding in a widespread, nefarious program to poison the planet from the skies."

On the plus side, this now means that chemtrails believers can move on to potentially more fruitful areas of inquiry, such as the question of whether Tupac Shakur is still alive and hiding out in Cuba.

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