I've been watching that show on the History Channel called "Ancient Aliens". The theory behind these ancient astronauts is that no, they did NOT build the pyramids. People built the pyramids. However, theorists believe that these ancient visitors DID tell us how to do it.
When the pyramids were built, mankind was not very technologically advanced at all, and it's believed that certain technologies were brought from alien travelers. Pyramids showed up all over the world, around the same time, long before man went exploring and discovered other civilizations and cultures. At the time, it was impossible for one people to share their knowledge with another people on the other side of the planet. These structures are all very similar in design and engineering, and some are actually identical to each other. There's no way the different cultures could have collaborated on the design and building of these structures at that time. It makes sense that someone was instructing humans all over the planet.
Scrolls and cave paintings show countless images of things that appear to be space ships and beings in space suits with helmets.
It's all very compelling, and in many, MANY ways, it's very logical. Much of the ancient astronaut theory seems to bring a lot of things together - at least for me. Ancient aliens being here actually clears up a lot of biblical stories in my mind. The theory kind of brings science and spirituality together for me.
I've been "losing my religion" for quite awhile here. I've lost "faith" because it didn't seem to be getting me anywhere. But listening to what people have to say about the ancient astronaut theory has really explained a LOT for me. I do have to say that some of the theories out there about the ancient alien visits are seriously ridiculous and too far-fetched to even consider, but on the whole, I find it to be very interesting, and extremely plausible. The evidence is there. You just have to go into it with an open mind and listen to what the scientists have to say. Seriously - much of it really makes a lot of sense and explains some of the unexplained.