My enthusiasm for alien visits waned a long time ago. I don't know what the current thinking is, but one of the big "proofs" were the figures from the plains of Nazca... those giant figures in Peru that you can only see from the air ... and that were "supposedly" used by the aliens as navigation aids.
First of all, it's all speculation what they were used for (if anything). The only thing they can really discern is that you can't really view them correctly except from the air. The fact they've found "jewelry" in the region that is 100% flight worthy aerodynamic (proven with scale models given a model airplane engine) tells me that alien or not (I happen to think it's entirely possible we've had a more advanced HUMAN civilization at some point in the past and perhaps they blew themselves up and/or some other disaster sent them back to the stone ages; imagine if we had a bad enough plague and most of the people running the power grids and other tech systems all died alone with say 75% of the population. Do you think the REST of us would be able to make it all work again, specialized sciences and all or would we all be too busy fighting to stay alive and end up technically inept within a few decades?)
In any case, the Ancient Astronaut idea is that the people of the Nazca region were trying to get the attention of the "gods" (aliens/technically advanced whatever beings) with the drawings knowing that they come from the sky they could see them there. It's not a "navigation aid" but primitive humans trying to attract the gods again to come back, the idea being they visited here, perhaps interacted or taught the humans some things and then left on for their next destination and these people wanted them to return again. I don't find the idea implausible at all as long as you find it possible that these more advanced beings could have visited. The rest is just basic logical deduction. Why else would you build HUGE drawings that could only be viewed from the sky? Exactly who else was supposed to see it?
It was pointed out to me that anyone able to navigate to the moon, let alone interstellar space, would be using something a shade more sophisticated than drawings in the sand.
The problem is this person that pointed this out had the wrong idea as to who was using them and for what purpose.
There was also the blocks of stone too big to move by hand. My father put a simple lever in my hand, and had lift his car. I was about 13 at the time, and the car was big. He told me to imagine what 100 big men with big levers could lift.
Yeah, well, there's a BIG difference between moving a two ton car a few inches off the ground and trying to move a two HUNDRED ton block 60 miles over uneven mountains with not even a tree line to make rollers with them (i.e. look up Puma Punku and the near laser cut precision an inset within inset designed "lego-like" blocks found there that we would have trouble producing today with our best equipment on that scale, let alone primitives mining it 90 miles away over uneven ground above the tree line carrying it up there one at a time and chiseling away perfect 90-degree angles with a level of precision that matches the best we could possibly do today. There is simply NO WAY ON EARTH those stones were made by primitives. Whether it was aliens or more advanced earthlings, the very idea the natives did it is downright ludicrous.
Places like Macchu Picchu have stones so closely put together (without mortar) they must have been melted to achieve that level of precision. Again, how did primitive man do that on the side of a mountain without a blast furnace to cook the rocks to the melting point? It makes no sense. Yet so-called "scientists" just dismiss it as primitives with rock shaped chisels when it's not possible to make them with chisels no matter how badly you want to do so.
And no simple "lever" is going to move a 50 ton rock on top of other giant stones at Stone Henge either not matter how many of those simple levers you get (in fact, trying to move them all at once makes it that much more unlikely they could coordinate their efforts precisely, let alone lift them dozens of feet into the air to put them into place. There are so many examples of giant stones that are just too big to place precisely today, let alone in ancient times (even with cranes!). A simple lever doesn't explain the 800 ton foundation stone found at the Temple of Jupiter (
http://www.world-mysteries.com/mpl_5.htm ). Just look at that photo and some of the 1000+ ton stones they did put in place at Baalbeck. That thing isn't going to move with a simple set of levers.
And I've seen plenty of theories about HOW something could be done, but very few examples to prove it and that's because no one want to try to build something like a pyramid using primitive labor methods. They'd waste their entire lives trying to figure out how to do it with such primitive tools, let alone build the Great Pyramid in half a lifetime.
A couple more examples like that, and I realized that best and biggest mystery was still why early people, for their own reasons, were doing these amazing things. And what people a 1000 years from now will be saying about us.
I don't know about 1000 years, but I can tell you that if we blew ourselves back to the stone ages tomorrow, certainly 12,000 years from now there wouldn't be much left of our civilization to find. All the skyscrapers, etc. would have fallen down and rotted in to piles of rubble. All the electrical goods, etc. would have disintegrated and the only things left would be STONE (and maybe styrofoam
) and things like gold jewelry. Yet when those future people get to the moon, they might just find some undisturbed evidence of our civilization. Would they reveal it or hide it? They'd probably conclude they were the center of the Universe for awhile too....
This planet has been here for BILLIONS of years. It is the height of human arrogance to assume we were the first intelligence species to ever evolve on this planet. Hell, the continents have rearranged themselves over that time and we think we would have found evidence? Sadly, though, we
have found evidence of a previous advanced (or visiting) civilization.
We ignore it. It was just humans who didn't even have the wheel that built those structures in Egypt. Nevermind the near 100% symmetrical precision of the statues in Luxor that simply COULD NOT have been done without automated manufacturing tools (a negative made of one half the face superimposed and reversed over the right half the face lines up EXACTLY the same; a level of precision IMPOSSIBLE with a mere "chisel"). It was just a bunch of guys with the desire to make giant statues and huge piles of blocks for some odd reason. There are rotary tool marks on many of the obelisks and statues. No, they COULDN'T have had a tool like that back then so IGNORE the marks and pretend they could chisel all that stuff with primitive rocks.
We've got people today that would DESTROY the pyramids even (and thus any record of them having ever been made if our own civilization some day fell) if they had the simple means to do so because they are a "pagan distraction" and so it's not hard for me to imagine a similar sect of people in ancient times wherein they would have destroyed that civilization back to the stone ages then too because no matter how advanced their or our technology becomes, you always have groups of people that think their particular "religious" beliefs are more important than respecting others' rights to exist or disagree with their beliefs. Their "god" demands they convert everyone to their particular or primitive stone-age beliefs (technology is evil, of course) or wipe them all out. This apparently impotent god never does anything himself so they are left with the dirty work, imagining what he wants from old books or their own imaginations that vary like storms across the earth's surface. Yes, I'm afraid we are a primitive planet indeed and yet we make assumptions about space travel being impossible over distances measured because we can't do it. Hell, we can't even figure out gravity properly and have to invent things like "dark energy" to explain why our mathematical models don't mesh between quantum physics and classical, etc. But no, we must be alone. The Catholic Church said so once upon a time!
Sadly....
All of this has happened before and it will (probably) all happen again.