The general consensus among Egyptologists is that the Sphinx was constructed somewhere between 2520 BC and 2494 BC. They also agree Egyptian civilization began circa 3100 BC. However, there are a handful of Egyptologists, geologists, and historians who suggest otherwise. They believe the weathering on the Sphinx's enclosure walls is indicative of water erosion rather than the commonly accepted belief that it was caused by sand and wind. If the weathering were caused by water erosion, it is so extensive that it could only be attributed to thousands of years of rainfall. Funny thing is, where the Sphinx is located is as bone dry now as it was in 2500 BC when it was supposedly built. In fact, the area has only experienced an average annual rainfall of one inch since the Old Kingdom circa 2686-2134 BC. Egypt's last period of significant rainfall ended between the late 4th and early 3rd millennium BC. If the weathering was caused by water erosion, the Sphinx must have been built during the 6th or 5th millennium BC at the earliest. If one accepts the water erosion hypothesis it must then be asked, how long was the Sphinx standing there before the heavy rains began? This is where academics diverge even further on the matter, and some believe it can be answered by astronomy. There is a wobble in the earth's rotation known as axial precession and it takes 26,000 years to complete a cycle. Because of this, the alignment of stars in the night sky is a cyclical process, so we are able to know exactly how the stars were aligned at any time over the last 30,000 years at any point on the earth. With this knowledge, we know that the layout and orientation of the Sphinx was a direct reflection of the constellation of Leo in 10,500 BC. Furthermore, it was at this time in 10,500 BC that the Giza pyramids were a direct reflection of the Orion constellation and the Nile River was a direct reflection of the Milky Way. So if one accepts the water erosion hypothesis they must also accept that Egyptian civilization is much older than believed, at least several thousand years older and in the case of the Leo Constellation theory almost 10,000 years older.