There are many plausible explainations for the pyramids, one is the time, the manpower which were substantial enough, then they had the maths for it, math that we had to rediscover (like pi). And there are systems of doing it, although youd have to exhaust your workers in unsafe conditions, which they were. Aliens? well, you may believe, but as with the bible, claiming it as fact would be just idiotic, which any alienbelieving pyramid theorists would admit. Christians tho? No, theyd go to hell, so they wouldnt ask questions even if they had them. Theyd find a way of explaining it without applying reason.