Dear Ian

I am somewhat puzzled by Kate Spence's paper. Maybe I am missing something, but I have been told by various people that the problem with dating using techniques such as hers or using precession in general is tectonic movement. There is some data on the subject published here on the internet by NASA.

Their figures imply a movement of some 200m in the Giza plateau, and possibly some significant rotation. Giza is moving especially fast because of its location at the meeting point of the African, Arabian and Eurasian plates, which also maximises potential rotation.

Another issue is the impact of the sea on the Giza plateau. The sea level has dropped two metres in the last 5,000 years which certainly will have affected the tilt of the plateau. In addition, there have been several tidal waves in the area. The one that crushed Cleopatra's Alexandria was massive, but probably not as big as the one resulting from Thera explosion in 1,500 BC. There are at least two Egyptian inscriptions which describe the devastating effect of tidal waves; the Tempest Stele from about 1,500 BC and the Medinet Habu inscription from 1,200 BC whose dating I think suspect.

With all this underground movement, I cannot see how Kate Spence can obtain such accuracy in her calculations - or am I missing something?

Regards

George Forrest