There was a highly technologically advanced civilization on earth more than 12,700 years ago. A comet impacted the western hemisphere around 12,700 years ago with enough energy to end the last Ice Age; cause massive extinctions of 324 species of animals; and cause the extinction of the Clovis people in North America.
The impact was so massive it caused the earth's crust to slip over the mantle in a manner predicted by Professor Charles Hapgood in his 1958 book with an introduction by Albert Einstein. The world wide cataclysm caused, among other things, the ocean of the world to slosh in its basin, creating the world wide floods reported by Noah and others. Sea levels rose as much as 400 feet at the end of the Pleistocene era. Only a massive comet melting in the atmosphere could supply that much water. Ancient pantheons of gods by the Egyptians, Greeks, Romans, Norse and others were in fact oral accounts passed down of the exploits of the advanced civilization which was destroyed 12,700 years ago. Stories of supernatural powers and magical objects, were in reality misunderstood high technology.
Ancient Alien Theorists have collected vast amounts of information concerning anomalous artifacts proving conventional theories are wrong. These Ancient Alien Theorists have postulated earth was visited by extraterrestrial aliens in the ancient past. In reality those presumed aliens were flesh and blood homo sapiens just like you. There are environmental reasons it is highly improbable that intelligent life has developed elsewhere in the universe.
Modern stories of UFO;s and aliens are cover stories designed to protect our national security by discrediting people who make UFO reports. The UFO's are indeed real. Many originate in the Skunk Works at Lockheed, and are flown by pilots from the CIA and the USAF.
The ruins of Atlantis still lie practically undisturbed under as much as a mile or more of Ice in Antarctica. It is probable the 1939 Nazi expedition to Antarctica, which claimed a vast swath of the continent as Neu Schwabenland, may well have recovered artifacts which were useful to them in having remarkable technological breakthroughs. Did they back engineer ancient technology?