The Great Pyramid of Giza, one of the legendary Seven Wonders of the Ancient World, has long captivated the attention of scholars who pondered on how many workers it took to erect this massive structure that weighs approximately 6 million tonnes and is comprised of about 2.3 million blocks of limestone and granite.
Yet while Herodotus wrote that some 100,000 men toiled to complete that project over the course of 20 years, and British physicist Kurt Mendelssohn in 1971 lowered these numbers somewhat to "70,000 seasonal workers and up to 10,000 permanent masons", yet another researcher, Professor Vaclav Smil, argued that "we can do better by appealing to simple physics", the Daily Express reports.
"The energy needed to lift the mass of the blocks above ground level is simply the product of acceleration due to gravity, mass, and the centre of mass, which, in a pyramid, is one-quarter of its height", Smil explained. "The mass cannot be pinpointed because it depends on the specific densities of the Tura limestone and mortar that were used to build the structure. I am assuming a mean of 2.6 metric tonnes per cubic metre, hence a total mass of about 6.75 million metric tonnes. That means the pyramid’s potential energy is about 2.4 trillion joules."
The professor then went on to estimate that a 70-kilogram man requires "some 7.5 megajoules a day" in order to maintain his "basal metabolic rate".
"Steady exertion will raise that figure by at least 30 percent. About 20 percent of that increase will be converted into useful work, which amounts to about 450 kilojoules a day. Dividing the potential energy of the pyramid by 450 kilojoules implies that it took 5.3 million man-days to raise the pyramid", Smil argued. "If a work year consists of 300 days, that would mean almost 18,000 man-years, which, spread over 20 years, implies a workforce of about 900 men."
The professor also calculated that about 2,500 additional men would be required to “place the stones in the rising structure and then smooth them over”, the newspaper adds.
"Even if we were to double that number to account for designers, organizers, overseers and the labor needed for transport, tool repair, the building and maintenance of on-site housing, and cooking and laundry work, the total would be still less than 7,000 workers", Smil surmised.