Pyramid Construction Theories

No one is really completely sure of how not just Egyptian pyramids were constructed but other civilizations like the Myans. One of the most commonly used theories used for the past few years has just been proven wrong which was the theory of hundreds of thousands of slaves worked everyday for 20 years until the pyramids were finished. But no matter how much man power you had you couldn't lift 2.5 ton stone blocks because they're wouldn't be any way to get fingers or anything under them to lift it and even if they could the slaves would have to be trained to walk step by step and in the same direction in a synchronized manner which would take forever.

The next most popular theory is the External Ramp and Crane Theory. This theory has been deemed wrong because the ramp would have to be no more than an 8 percent slope for it to be possible to transport the blocks. At an 8 percent slope the ramp would have to be 1 mile long to reach the top of the pyramid. This would prolong the amount of time it took to build the pyramid because you would have to make an enormous amount of calculations and then build the ramp. And there is no evidence what so ever of a structure so large. The Egyptian cranes were made out of lumber which was imported because they didn't live near many forests. The idea of exporting so much lumber is ridiculous and would also prolong the time of construction for the pyramids because it would take years for the lumber to get there and for the cranes to be built. And the idea of having multiple cranes big enough to lift 2.5 ton stone blocks on different levels of the pyramid is absurd.

The most recent and widely accepted theory is the Internal Ramp theory. This theory suggests that Egyptians had a ramp that spiraled upward and is still present in the pyramids themselves.
http://www.archaeology.org/0705/etc/thumbnails/pyramid4.gif

Another controversial theory is that Aliens helped build there pyramids. Most if not all of the civilizations that had pyramids spoke of  "Those that came from the sky" and I'm sure they weren't talking about birds. Some say that they were Aliens others say that they were the gods that they worshiped. who really knows? These theories interest me and I would like to hear what you guys think maybe we can have a class discussion or something?