The Annunaki are my favourite as they wrote about beings coming from the 10th planet in the solar system visiting us every 2,750 years.
An experiment that takes millennia? I find that difficult to swallow. What would be the point in wasting all those resources on something that would take so long, especially because if their own culture took so long to develop, they would know of the enormous time spans involved.
I don't really have a dog in this fight, but I would like to weigh in on the matter of time and distance.
If I'm not mistaken, Einstein's Special Theory of Relativity basically says, as you approach the speed of light, time passes much more slowly than if you were at rest.
So, the Ancient Astronauts who were mining gold and reprogramming human DNA about, what did onosson's link say? 12,000 years ago? Anyway, so the AA's ran out of Marlboros and Heineken and needed to go home and load up at Circle K. They wanted to hit the casino anyway and bet the a$$load of gold they just raped from Earth on the Orion Octopi in next Sunday's championship Black Hole Bowl. Two of the AA's are the rhythm section of the half time band and need to rehearse. So they load up their gear, wave goodbye to the Annunaki and head for home in their Interstellar OverDrive.
Most of the AA's lost their Au in an intense defensive battle for the title, the band, however, slayed the stadium and everyone partied long into the night. Monday afternoon, still slightly hungover, they pile into the IOD and head back to good ole Terra...
where they discover that 2,750 Earth years had transpired in their absence. Maybe they feel the gravity of their cultural impact; they resolve never to return and let nature take its course. Perhaps instead they are watching, and waiting for us to become worthy of chilling with. Maybe guys like hdracer and half the deck watch get to see them sometimes. Maybe when we are ready, Earth will get invited to send a team to the Black Hole Bowl.
Who knows? Fun to think about though, isn't it?