These days it's a common sight: hazy streaks crisscrossing the sky left from passing aircrafts. But many people believe there’s something more going on. Dubbing the contrails “chemtrails,” conspiracy theorists have claimed that these trails of condensed water are part of a secret program to control the weather, change the climate or control our minds.

Conspiracy theorists have amassed huge dossiers of “evidence” claiming that chemtrails are longer, brighter and do not dissipate as quickly as normal aircraft contrails. They have photos, anecdotes and samples collected from the air and water. Though scientists have long battled against these unfounded claims, they haven't made much headway. But with a recent study, researchers from the Carnegie Institution for Science hope to put these rumors to rest.

The researchers provided the available chemtrail evidence to 77 atmospheric scientists and geochemists for evaluation. “I felt it was important to definitively show what real experts in contrails and aerosols think,” Ken Caldeira, an atmospheric scientists and author on the study, says in a press release. “We might not convince die-hard believers that their beloved secret spraying program is just a paranoid fantasy, but hopefully their friends will accept the facts.”

In the study, published in the journal Environmental Research Letters, the scientists were asked if they had ever uncovered possible evidence of a government chemtrail program in their research. Of the 77 scientists, 76 said no.

They were also shown photos supposedly containing chemtrails, writes Sara Emerson at Motherboard. Upon inspection, none of the researchers saw any evidence that the contrails in the photos were any different than normal contrails.

Finally, they were presented with the analysis of samples from pond sediment, snow and air that the collectors claim were contaminated with traces of barium, aluminum, copper and strontium from chemtrails. The researchers said that 80 to 89 percent of the samples could be explained by phenomena much more simple than chemtrails.

The chemtrails craze likely originated with a 1996 report from the Air Force called “Weather as a Force Multiplier,” which speculates how the military could develop weather modification technology by 2025, report Annalee Newitz and Adam Steiner at i09. A patent filed in 1991 for a technique of seeding the upper atmosphere with particles that could reflect sunlight and slow global warming also intrigued theorists. Combined with anecdotal tales of plants dying and people getting sick after planes left contrails above their homes, the conspiracy theory coalesced and took off on the internet in the late 1990s.

Since then, the issue periodically pops up in the media. According to Public Policy Polling, about five percent of Americans believe in chemtrails. That’s more than the four percent who believe lizard people are taking over our politics but much less than the number who believe in bigfoot or that global warming is a hoax.

So, if it’s not a government program, why do many people claim to see more and more contrails? Emerson says airplane contrails are likely lasting longer than they used to due to changes in jet engine technology. In addition, an increase in air travel over the last couple decades could also be fueling the belief in chemtrails, says Caldeira, and atmospheric changes from global warming may cause the artificial clouds to linger longer than they used to.