It's one of the most polemic subjects of ever: is there more intelligent life in the Universe or not? There are, around the world, several theory supporters defending the existence of alien civilizations which are following closely the human evolution and that they even visit us occasionally since a long time ago. This supposition is fascinating but, if such a thing happens, where are the evidences of these visits? This is a delicate point: find a proof that an UFO visited us. The supporters of these theories, with the photography appearance, in the 19th century, won a precious assistant.
There are hundreds and even thousands of photographs made until our days portraying strange shapes floating in the sky above houses, landscapes and in airplanes' persecutions. Almost all of these shapes are similar to a disk, what originated its common expression "flying disk". However, serious scholars prefer to baptize these appearances with the technique name UFO (unidentified flying object).
With this extraordinary quantity of photographs, an equal extraordinary quantity of people has been dedicated on studying them, aiming to verify its veracity. There are several conclusions. Some were truly a deception: they are manipulated images (note: it was verified a long time before the digital images' appearance and their concerning edition software -- they were photomontages, composite pictures). Others, instead, resisted to all kinds of analysis and demonstrated no sign of interference -- so, no tricks. They are the most disturbing and intriguing.
The UFO evidence website has, among several other things related to the theme, an amazing collection of UFOs' photographs, which some of them are showed there.