The pyramids, made of stunning white limestone and designed as magnificent tombs, were built to keep the dead's secrets forever. For thousands of years, they've inspired limitless myths and legends and raised true scientific questions. How did such wonderful buildings rise so high with such accuracy? Why would a civilization spend so much time honoring their dead? Who were the millions of laborers who moved billions of tons of stone? Today scientists are discovering facts behind myths related to the pyramids.
Stretching high over Cairo like old sentinels, these pyramids stood built more than two millennia before Christ, and still they continue to fascinate us. They present a vast space of exploration to archaeologists eager to know how they were made and what for. Egypt captivates our imagination to some extent as they were also able to avail themselves of the use of stone, and their world had its first skyscrapers. Unfortunately, the engineers did not pass on a complete set of guidelines on how exactly they constructed them, and so many centuries worth of legend now obscure what purpose they really served. The pyramids themselves are the only evidence we have left, inviting scientists to examine the stones in hopes of discovering where they originated and who constructed them.
These incredible structures were constructed with basic, primitive technology, but they are remarkable feats of engineering. Look at the Great Pyramid, for instance—it rises 480 feet into the air and is constructed of approximately 2.3 million stones, some weighing as much as 50 tons. The entire structure weighs almost 6 million tons, equivalent to 16 Empire State Buildings. It stood as the tallest man-made structure in the world for 3,800 years. More striking, however, is its precise engineering: the sides measure 755 feet long, with under two inches deviation in length. Inside is a complicated maze of corridors and chambers built out of some of nature's toughest stones. The block fit is so precise that no credit card can be inserted between them—all the work of a civilization that hadn't yet discovered the wheel.
The accuracy of the Great Pyramid astounds me. Early Egyptologists attempted to blast their way into the pyramid's secrets using explosives, likely destroying invaluable clues left by ancient Egyptians about the construction techniques. New archaeologists today are using sophisticated technology to reveal concealed treasures in the stones. I truly believe the king's tomb is still concealed within the pyramid, but for most archaeologists, the structures themselves are the biggest shock. What is truly incredible isn't so much the concealed chambers; it's that the Egyptians managed to do this with such minimal technology.
Building pyramids was a process for the ancient Egyptians; it wasn't completed overnight. They worked their way up, moving from simple mud huts to the intricate patterns of the Great Pyramid at Giza. The first pyramids appeared on the west bank of the Nile in 2600 BCE, and the first structure was the Step Pyramid at Saqqara, likely the world's oldest stone structure at 204 feet tall. This was a radical leap forward in building style, with step-like form instead of smooth curves.
Only sixty years afterward, Pharaoh Sneferu built the first true pyramids with flat sides, and subsequently his son Khufu built the Great Pyramid—the largest of the three at Giza. Then a succession of smaller but highly decorated pyramids began to appear at Saqqara. How the Egyptians managed to build these gigantic structures using their crude tools is still a question in our minds.
The first task was figuring out the orientation of the site and positioning the pyramid in such a way that it was aligned. They chose the site with utmost care to make sure that the bedrock could support millions of tons of limestone. The ancient architects approached all this with meticulous detail so that each side of the structure matched the cardinal directions—north, south, east, and west. While we’d rely on digital compasses and laser technology today, the ancients likely used observational methods, tracking the rise and set of stars to find true north. They built a semicircular wall to mimic a flat horizon, marking star positions as they rotated around where north was. By drawing a line between these markers, they were able to position the pyramid with amazingly accurate precision—off true north by less than 1/20 of a degree.
Pyramid builder Robert Bovale, who is an expert at aligning modern buildings, is amazed at how precisely the Egyptians did it. "I've used optical devices and cranes to align buildings and sometimes I don't achieve that level of precision," he says. Having established true north, the workers placed an alignment indicator for one corner of the pyramid base, doing it again with measurement rods and strings.
With the layout planned, the engineers excavated a level foundation from bedrock to support the massive structure. A perfectly level base was needed for a solid pyramid. British engineer Dennis Stocks, an expert in ancient construction methods, suggests that the Egyptians might have leveled the foundation with water. They may have excavated a channel across the 755 feet of the pyramid side and filled it with water to utilize as an ad hoc spirit level. Along the water line, they leveled and made the base flat.
In an attempt to maintain that plane as they built upwards, the Egyptians cleverly devised another invention. This simple wooden device was two pieces of wood in right angles attached by a crossbar and a hanging plumb line. By placing it on the surface of the water, they could determine a horizontal plane by finding the point at which the line dropped into position against a designated mark.
Now that the land was leveled and prepared, they could start constructing. This was no small accomplishment, with millions of tons of stone, but how did they manage to gather so phenomenal an amount without the use of modern devices like dynamite or jackhammers? More than 500 years in the Old Kingdom, 18 massive pyramids were built utilizing an unparalleled quantity of stone that needed to be quarried, cut, and transported. This would have been a tremendous undertaking even for today's engineering companies employing advanced machinery, but the Egyptians accomplished it under primitive conditions utilizing basic tools.
Stocks has gone to Toura, near Cairo, where many of the pyramid's high-grade limestone was sourced. He believes the Egyptians cut this stone using copper tools. By replicating some of those old copper chisels, he believes he's closer to understanding what was going on inside those workers' heads. But since copper is a soft metal, it can be bent or worn out quickly—how did they manage to cut through limestone?
With a copper chisel and mallet, the ancient workers would hit at an angle against the stone, essentially chipping off pieces for rough shaping. They also had finer chisels for more intricate work, carving surfaces to almost perfection. Stocks's studies have proven that it is actually possible to carve limestone blocks with soft copper chisels. Interestingly, the careful study of ancient tools revealed that the Egyptians' copper was not pure but contained traces of arsenic. The unexpected impurity actually toughened the copper, giving the stonemasons the ability to quarry the majority of the 2.3 million blocks of limestone for the Great Pyramid.
While the majority of the pyramids were built of relatively soft limestone, harder granite was applied in critical locations like the king's chamber. It is an easy thing to do with modern tools, but the Egyptians did not yet have iron, and archaeologists for centuries have been puzzled over how they cut these huge 50-ton slabs of granite. Experimental archaeology is only now coming up with solutions to this intriguing technology puzzle.
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