Look! Up in the Sky! A History of Recent UFO 'Sightings'

CREDIT: April 30th 2011 - UFOs pause and reverse direction. Ed Grimsley's UFO Nightvision View full size image

Ever since the first UFO sighting back in 1947, people have been turning bright streaks, floating orbs and strange sets of lights in the sky into proof that we're being visited by extraterrestrial beings. Here, a list of some of our favorite UFO sightings, starting with that original report of a flying saucer that wasn't .

• Does this video show proof of UFO battles ? Not likely, but wouldn't that be cool?

• Not all UFOs are spotted in the sky. Here's one that was found on the ocean floor .

• Hey there, conspiracy theorists: CIA Cover-up Alleged in JFK's 'Secret UFO Inquiry'

• Did UFOs terrorize cowboys the Wild West ? Probably not, but there was at least one Texan running alien hoaxes at the time.

• X Files opened. The National Security Agency spills its beans.

• This one is great. According to some military documents, a 1968 UFO sighting raised questions over whether aliens might have tried to detonate our own nuclear warheads .

• Not a UFO sighting, but there's a long history of seeing unfounded signs of life on Mars .

• Where there are UFOs, there must be aliens. Unless you're looking for aliens in Antarctica .

• Ball lightning is one of the most common explanations for UFOs. Ball lightning.

• Strange clouds are another common explanation, and probably the root of this UFO sighting over a Chinese airport .

• Sometimes, UFO sightings have really, really lame explanations. Example: This UFO report from Manhattan.

• Other times, UFOs are private rockets. Maybe.

• Or perhaps that UFO is just a really bright Venus.

• UFOs spotted over California ? A lesson in proper use of night-vision gear.

• Some strange lights in Colorado lead to a string of UFO reports earlier this year.

• Pilots are often the first to spot UFOs, such as this UFO report from O'Hare airport in Chicago.

• If it's not a UFO, it must be a secret military plane, like these "black triangles."

• Remember the "alien autopsy"? Here's the story behind that elaborate hoax.

• It's a good reminder that aliens might not be a bad thing. Some scientists suggest that aliens could fix Earth's global warming .