Neil deGrasse Tyson Doubts Aliens On Earth, Gov. Couldn't Keep It Secret

Neil deGrasse Tyson is happy UFOs are being taken more seriously by our government ... but he highly doubts we've been visited by aliens, and he's got one big reason.

We got Neil at LAX, and he jumped on the subject of aliens visiting planet Earth, saying it's highly improbable out-of-this-world visitors could escape omnipresent video from cellphones.

Neil says he'd love for our government to be more open about any recorded phenomenon, but he doesn't think a full-on invasion has gone down that officials are keeping a secret.

In case you missed it, former New Jersey Governor Chris Christie had a laugh during the Republican debate over UFOs... but promised to give Americans the 411 if he gets elected.