A secret Ministry of Defence report on Unidentified Flying Objects (UFOs) has concluded that they DO exist - but they may not be crafts from other worlds.
The research, which took four years, suggests that flying saucers and other UFOs are actually created by natural phenomena - caused mainly by light.
These include things like plasma, ball lighting and vortices-as well as odd shaped balloons and aeroplane lights!
The MOD always denied UFO studies but this report shows 50 years of research.
The 400-page report, which has been made available to the public for the first time, says: "No evidence exists to suggest that the phenomena seen are hostile or under any type of control, other than that of natural physical forces."
This explanation will not satisfy everyone though - especially those who claim to have seen UFOs.
Some UFO spotters believe governments cover up the truth about UFOs because they are afraid to admit there is something beyond their control.
UFOs, or Unidentified Flying Objects....are they real, or imagined? Have you spotted a UFO, or is it all a load of made up rubbish? Send us your UFO sightings or thoughts.
I think that the kind of aliens we read about do exist because there are billions of other stars so there must be more life than just us.
Rhianon, 13, Bristol
I don't really know whether they exist or not but I like to think that they do, as it's something to debate about.
Vincent, 10, Loughborough
I do not believe they are real because whilst people may argue that we could not be the only planet with life I think we are, in fact, the only planet with the perfect conditions for life. Also, I am a Christian, and my religion teaches that Earth has the only life.
David, 14, Belfast
I think aliens do exist because why would there be one planet with life and millions of other planets and stars without life?
Zac, 11, London
I do not think that UFOs are real. I think it is just a tornado up in space spinning objects about!
William, 12, Manchester
I think don't think that UFOs and aliens exist.
Abaid, 14, Manchester
I have seen UFO's over 10 times. I think the best times to see them is in winter and at sunset in the summer!
Michael, 11, Tamworth
The government says it's natural phenomena but this could be another cover up story!
Graham, 12, East Kilbride
I think it's extremely creepy that there are UFOs because I hate the thought of an alien invasion.
Prisma, 11, Unknown
I think UFOs do exist because there is a whole universe out there. There is probably other life forms wondering about us and who we are!
Max, 11, Bracknell
My friends and I noticed something strange in the sky and later on that night my friend looked at it through a telescope and said it was like a UFO inside a bubble!
Graham, 12, East Kilbride
It's all silly. If aliens are planning to invade Earth, why haven't they already done it?
Dana, 11, Copper
I think that UFOs are a pile of nonsense and even if they are real they're not doing any harm. So just leave them alone!
Saadia, 12, London
It's all rubbish! No UFOs or aliens exist.
Tom, 12, Scotland
On the news you sometimes hear about people who believe they have seen UFOs. I don't think there is much truth in the alien idea of UFOs - at the moment!
Megan, 13, Unknown
I have seen a big black thing flying over my school. It was in a shape of a saucer and it almost looked like metal.
Tom, 9, Woodhall Spa
I think UFOs are real but people think I'm crazy!
Charlie, 9, Datchworth