As the world marks UFO Day, here are 7 of the most convincing alien conspiracy theories

FOR centuries, conspiracy theorists have been fighting to prove that alien life exists.

From numerous UFO sightings to allegations that NASA has been destroying data, there’s been oodles of information that’s sparked furious debate.

In celebration of UFO Day, here are 12 extraterrestrial pieces of evidence that suggest that we’re not alone in this universe...

1. A NASA cover-up?

Earlier this year, conspiracy theorists accused European space agency NASA of hiding extraterrestrial information from members of the public.

Several UFO enthusiasts claimed they saw a black cube “orbiting the sun” in a snap taken by the European space agency’s Solar and Heliospheric Observatory.

Posting the ‘evidence’ online, the YouTuber explained: “More and more people on Earth, see the mysterious phenomena in the sky, as well as unidentified flying objects."

Another accused: "It’s definitely another interesting find and once again directly after it appears NASA cuts the feed.

"That's why you see the screen go blue. They’ve done this, they have been doing this, and they have their hand on the chicken switch as they call it."

2. Medieval evidence

A painting which dates back to the 17th century could be the very first depiction of a UFO.

The 400-year work housed in the Monastery Church in the Medieval Citadel in Sighisoara, Transylvania has left tourists scratching their heads.

Nigel Watson, author of the Haynes UFO Investigations Manual said: “Flying saucers, UFOs and other weird objects in the sky have been depicted throughout the history of humanity.

“What appear to be UFOs and aliens appear in the cave paintings of ancient man, the religious paintings of the Renaissance period and in the works of chroniclers and storytellers."

3. Astronomical probability

A number of astronomers have claimed that it’s highly likely we’re not alone in the universe.

One of the most famous theories came from astrophysicist Frank Drake in 1961.

The pioneering scientist formulated an equation that estimated the likelihood of extraterrestrials existing.

In 2001, he released the statistics, which showed that hundreds of thousands of alien planets could technically exist.

4. Astronauts believe

One of the most compelling accounts of an extraterrestrial sightings comes from Apollo 11 pilot Buzz Aldrin.

A report by the Science Channel reported that the astronaut, who was one of the first two humans to land on the moon, spotted a spacecraft on one of his missions.

Allegedly, Buzz isn’t the first astronaut who believes in extraterrestrial life.

Captain Edgar Mitchell, from the Apollo 14 mission, revealed: "I happen to be privileged enough to be in on the fact that we have been visited on this planet and the UFO phenomenon is real.

“It has been covered up by governments for quite some time now."

5. UFO sightings

There have been dozens of alleged UFO sightings that have swept the internet already this year.

Earlier this month, holidaymakers were left terrified when a ring-shaped UFO was spotted floating above the iconic theme park in California, USA.

Kyle Hawkins, who took the video, described the reaction of park visitors at the appearance of the floating object, claiming that people “half expected an alien portal to open up through the ring”.

The bizarre footage emerged just days after YouTube channel SecureTeam10 released a video which allegedly showed an unidentifiable ‘space craft’ hurtling through our solar system

6. The Roswell case

In 1947, one of the biggest extraterrestrial controversies occurred following a crash at a ranch near Roswell, New Mexico.

Theorists believe that the US government covered up the crash of a spacecraft, with some even believing that the remains of an alien were recovered.

Despite some evidence pointing to alien life, authorities insisted that the spooky incident was merely a crashed weather balloon.

7. A government cover-up?

Statements released by government authorities have been a hot topic of discussion for UFO enthusiasts.

Former director of the CIA between 1947-1950, Admiral Roscoe H. Hillenkoetter, said: “Unknown objects are operating under intelligent control... It is imperative that we learn where UFOs come from and what their purpose is.”

Another memo that also emerged in 1947, from USA Air Force General George Schulgen, said that UFOs were “real and not visionary or fictitious”.