The other theory is the Alien theory. This theory suggests that extra-terrestrials helped the Egyptians build the pyramids. If you think about it, how could anybody that didn't have any machines lift two to five tons by themselves? This theory thinks that the aliens helped them, but why they did would still be unexplained. This theory has many interesting facts to support it though. Around some of the pyramids there is radioactive sand around them, maybe the aliens used this to communicate to the Egyptians, for some reason. Also, there are corresponding landforms on the face of Mars. One of these landforms resembles a human face (see below picture). Could have aliens from outer space helped the Egyptians build these pyramids, or were they constucted by themselves? I guess until then, we will never know.