First of all; when Joseph was appointed to save Egypt from the coming famine, he had 7 fat years in which to store up grain for the coming 7 years of famine. They had to build granaries quickly. Each of the pyramids took DECADES to build using slave labor. The famine would have been upon them before the first pyramid was half built.
Secondly, The pyramids are practically useless for grain storage. They are just huge rock piles, solid stone upon stone, except for a secret passage entrance, and a few smmall burial rooms that are practically inaccessible. They were designed to be entered one time, for the funeral of pharoah, and then sealed shut forever. There’s no place in that nearly solid rock pile to store more than a few bushels of grain.
The pyramids were NOT for storing grain. I cannot believe an intelligent man such as the good doctor would utter such nonsense. He obviously gave no consideration or thought to the construction of s pyramid. It isn’t hollow and spacious. It’s a nearly solid heap of humongous stones.
“They were designed to be entered one time, for the funeral of pharoah, and then sealed shut forever.”
Except there is no evidence that the pyramids at Giza were ever used for that purpose, nor that they were meant to be sealed forever.
Nor were slaves used to build them - those that worked on the complex were well paid, fed, and cared for - it was an honor to work on them. You cannot understand the complex if one thinks of it as a Christian, rather one must think like an Egyptian of the Old Kingdom, which means to think symbolically not logically; this is sort of like asking a aborigine hidden in the Amazon to understand social media, only that is an easier task.
Did you know that the interior of the Giza Pyramids reflect sound in perfect harmonics? Or that the whole Giza complex was designed as one structure?