Have you ever noticed those white smoke trails left behind by jets in the skies?

Well, they are actually called contrails, and some people have been talking about what they may really mean.

There are many out there who believe those contrails are part of some kind of government experiment, to either reduce global warming or block harmful radiation from reaching the Earth.

Kiii News has been contacted several times by people who are concerned about the contrails in the sky. One man said he believed the government may be putting chemicals into those exhaust trails to shield us from future dangerous radiation produced by a passing asteroid.

The government has received thousands of complaints over the years, and they say the fears are unfounded.

David Bridges, an associate professor at Texas A&M University-Corpus Christi, has a PHD in aeronautics from Cal Tech. He said there is nothing to the chem-trail conspiracy going around. In fact, he calls it an urban myth, and said it has been around for years and surfaces from time to time.

However, he did say that there is some research into those white smoke trails in the sky.

"There has been some discussion that the contrails may contribute to climate change, global warming," Bridges said.

Bridges said that the jets put out carbon dioxide, which is a greenhouse gas, and that they do help to increase the cloud cover a bit, and that tends to drive global warming; but it is not believed to be a big enough problem to merit serious concern.

So again, there is no scientific proof that the contrails are anything more than artificial clouds made by jets as they streak across the sky.