How have the Egyptian pyramids lasted so long?
Structural engineer Steve Burrows tells us how Egypt's iconic pyramids were built to last for thousands of years.
How can we learn more about history’s greatest buildings and the methods used to construct them? One way is 3D laser scanning, which captures the ruins in all their glory and recreates virtual replicas.
As one of the engineers involved in making the Beijing Olympic stadium, you’ve been part of one of the most exciting modern-day builds. What do you find most inspiring about the ancient pyramids?
The amazing thing about the pyramids is their longevity. If you asked us to build something today, and you wanted it to last for 5,000 years, then we’d think you’d gone crazy. I mean, how could you possibly do that?
Also, the Great Pyramid represents an evolution in building. By ordering the pyramids in time, and putting them next to each other – something our software could do with the laser scanning data – we can see how the Egyptians learned. They passed knowledge from one pyramid to the next, and just got better – until the pinnacle of pyramid building, the Great Pyramid, which is almost the limit of what is possible.
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What was different about the Great Pyramid that made it last so long?
Before the Great Pyramid, the Egyptians hadn’t cut the stones accurately enough to make the joints really tight. They had problems with what’s called ‘freeze thaw’. This is when moisture gets into the joints, so if the weather gets cold enough, the water freezes, solidifies and expands – pushing the joint apart.
That cycle of the joints being opened and closed effectively makes buildings fall apart, and we have that problem today. The Egyptians had realised that – they knew that if they could construct joints so tight that water couldn’t get in, then the building would not destroy itself and it would last a long time. They did this in the Great Pyramid.
In addition, they used stone like granite: a material so hard that it wouldn’t act like a sponge – the water didn’t penetrate it. So, the stone would shed the water and the building would last longer.
One of the things we learned is that these people were very intelligent, continuously educating themselves and making things better. There was an incredible amount of thought gone into these monuments. It wasn’t a great experiment; it was the application of science.
James is staff writer at BBC Science Focus magazine. He especially enjoys writing about wellbeing and psychology.