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Due to the harshness of space travel, some aliens may be mere shells or clones with artificial consciousness.
In the spring of 1952, a spike in UFO sightings is so extreme that it forces the U.S. government to confront the phenomenon head on.
Some say documents reveal that government agencies have been hiding important UFO sightings for decades.
Some believe that America has a secret Space Force with ultra-high-tech ships for missions beyond Earth's orbit.
Fighter pilots scramble to intercept UFOs; advanced, unknown technology threatens Earth's airspace, and there is little anyone can do about it.
Governments around the world investigate UFO sightings, but many of them keep it a secret from the public.
Alien abductees reveal details about the insides of UFOs and help researchers understand how aliens live and what they want from the human race.
Aliens may be interested in experimenting on the human mind and body; human civilization may be aliens' prized experiment.
Mankind must find a way to navigate the galaxy in order to survive; how alien spaceships complete interstellar travel.
Evidence of alien presence on Earth; humans and aliens may be one and the same.
As technology advances, more and more people are capturing images of inexplicable objects in the sky.
Examining the possibility that UFOs may be from Earth.
A series of UFO sightings in 1947 propels the phenomenon to the world stage; the U.S. Air Force concludes that UFOs may not be from Earth.
In the court of public opinion, the most credible UFO witnesses come from law enforcement.
Space Shuttle cameras record UFO footage that many experts find almost impossible to explain.
Some UFO sightings take place over large cities and have hundreds of witnesses.
Whether life remains on Mars, and how it may have evolved.
It may take aliens millennia to answer humans' call.
Some believe that mankind's survival hinges on the science of artificial intelligence.
Where alien life may exist, and what it may look like.
To get to Earth, UFOs must withstand an endless frozen void, intense radiation and blistering heat, and some appear to have failed to reach their destination.
Fear takes a new shape: the rise of Black Triangles.
Shortcuts through space may allow travelers to span vast distances in the blink of an eye.
Derelict spacecraft; the face on Mars; alien civilizations in our solar system.
Adolf Hitler and the Nazis may have used alien technology to transform their army into a strike force of unprecedented power.
Eyewitnesses come forward with unsettling stories of alien bodies recovered from crashed UFOs.
A few locations are notorious for strange physical and paranormal phenomena related to extraterrestrial activity.
Researchers demand that the government reveal what is known about UFOs.
Individuals all over the world report close-encounter incidents with alarming increase.
The terrifying capabilities of alien weapons; how humanity can fight back in the final battle for planet Earth.
A powerful top-secret organization is said to control all UFO information and to keep even the highest levels of government in the dark.
In 1965, hundreds of people witness a fireball crash in rural Pennsylvania.
UFOs appear to burst from the ocean into the sky.
In 1948, a fireball crashes near Laredo, Texas.
Abductees say aliens have captured and experimented on them.
Ancient megaliths baffle historians and engineers the world over, leading some to believe that aliens had a hand in building them.
Aliens may be plotting to plunder the Earth's natural resources.
Alien life may be attempting to communicate with humans.
America's recent, massive blackouts may have been caused by alien technology.
Aliens may be causing global climate change in order to make Earth hostile to human life.
A united Earth may be the only chance for survival in the face of an alien invasion.
Crashed UFOs may contain alien technology that could change the course of history.
Citizen ufologists coordinate alien information-sharing networks, subverting their governments' classified intelligence.
Ufologists discuss what UFOs may be, where they may originate and what may be their agenda.
Abductees report torturous medical experiments involving removal of human biological samples; aliens may be creating human hybrids.
NASA denies UFO accounts and takes measures to prevent astronauts from telling their stories.
Some believe that extraterrestrials cause atmospheric light-shows and question whether they pose an imminent threat to humanity.
Millions believe that extraterrestrials live on Earth; an alien enemy may orchestrate a doomsday scenario.
The world's military forces have come face-to-face with thousands of unidentified objects; military encounters between Earth's armed forces and UFOs.
UFOs may endanger commercial airliners; midair abductions; near-disasters caused by unseen enemies.
At times, UFOs appear in the sky faster than authorities can track them.
Millions of people may be alien abductees without being aware of it.
Both aliens and Earthlings may secretly possess advanced antigravity technology.
A mysterious book outlines decades of cooperation between the U.S. military and alien forces on Earth, as well as a massive government cover-up to hide the visitors from the world.
Aliens may have tried to make contact with Earthlings for millennia, and a message may have been decoded.
Many UFO events take place in Los Angeles.
One of the most sacred places on Earth may house secret knowledge of extraterrestrial life.
Tampered space-photos, missing NASA recordings and a race to the moon may point to the possibility that alien life exists.
Throughout history, unexplained illnesses have repeatedly attacked the human population with a vengeance.
Ten tales of aliens, UFOs and abductions; a fresh look at classic encounters and several new stories.
Aliens may have created the means to control humanity.
An extraterrestrial source may have helped Adolf Hitler in his attempt to conquer the world.
Members of the federal government may be aliens with sinister purposes in mind.
A shocking photograph with no plausible explanation; an aborted nuclear launch; the continuing appearance of mysterious men in black.
U.S. presidents may have knowledge of extraterrestrials.
Ancient Egypt, a civilization millennia ahead of its time, may have had extraterrestrial help in building its masterpieces.
Aliens' plans for the human race may be peaceful or not.
Sentient life may have begun on Mars and traveled here.
UFO enthusiasts and abductees report the strange appearance of ominous investigators after sightings.
Earth's armed forces may face a new enemy that is literally out of this world.
Ground zero of the explosion of UFO sightings is the desert of the American southwest: Roswell, N.M., and Area 51.
Governments all over the world may harbor extraterrestrial life in remote and forbidden places.
The British government may know more about alien invasion than it is saying; military cover-ups; dire warnings from government insiders.
Some UFO enthusiasts believe that all signs point to a massive global cover-up; the most active alien hotspots on Earth.