It wasn't aliens that built the pyramids, rather just some clever engineering. New discoveries about the pyramids in the last two decades have given researchers deeper insight into how the ancient Egyptians may have constructed them.

Grasping the size of the pyramids

The largest and first pyramid at Giza was commissioned by the Egyptian pharaoh Khufu somewhere around 2551 B.C. His pyramid is known as the Great Pyramid and stands at 455 feet (138 metres) tall. It's considered to be one of the seven ancient wonders of the world.

The next pyramid was built around 2520 B.C. for the pharaoh Khafre. It's slightly smaller than the Great Pyramid but elevation wise is taller thanks to a higher base. The final pyramid was built by a pharaoh named Menkaure around 2490 B.C. His pyramid was the smallest, standing at only 215 feet (65 m) high.

These structures, mainly the Great Pyramid, stood as the tallest structures ever built for 3,800 years – much of recorded human history.

Focusing in on the Great Pyramid, the biggest of the bunch, it is made up of about 2.3 million stone blocks all on one foundation. This foundation is an engineering marvel all by itself.

The Egyptians levelled the massive base to a tolerance of two centimetres using what was likely a series of levels they constructed from right-angled beams. It's also square within 11 centimetres on every corner. In all reality, the pyramid's base was probably the largest flatted square ever constructed on earth at the time.

Another interesting fact about the foundation is that its sides are perfectly aligned with the directions on the compass. Compasses didn't actually exist back then and the North Star wasn't in the same spot. Egyptian engineers would've tracked the path of stars across the sky and then bisected the arcs to find true north to align the foundation.

Once the foundation was constructed, the engineers and workers could move on to building the main structure. The pyramids are made from limestone which was quarried right next to the building site. But how did these workers extract such large blocks from the ground? They used the natural geology of the quarry.

The thickness of each block was determined by the thickness of the limestone layers in the quarry. These lines would naturally separate with less force. Workers would dig channels down the side of the stone, then use large pry bars to create cracks that would eventually fracture. In cases like the great Sphynx, this structure was actually dug from the ground and sculpted in place.

This construction method is one of the main ways scientists have been able to extrapolate that ancient engineers used the natural limestone layers for block thickness.

How were the stones moved?

As for how the stones were moved, researchers recently came to the conclusion that Egyptians likely used sleds that were pulled over damp sand to reduce friction. This technique would've allowed the pulling force to be reduced by 50%, thus cutting down on the effort needed to move the stones.

The great pyramid was built in about 23 years, a span of time that makes many think that workers never could've completed the project without external help. However, when you break down the maths, you see that it can actually work.

In order to produce the amount of stone for the pyramids, an Olympic sized swimming pool would have needed to be quarried every week. Modern testing shows that this could've been done with as little as 1,200 workers, which is certainly within the realm of the workforce that engineers had access to at the time.

Once the large stones were quarried, they would have needed to be moved into place on the foundation. Modern engineers have determined that there was likely a large ramp that spiraled around the pyramid at the bottom that then got smaller as it got built up.

The stones would be pulled up the ramp using the sleds and then moved into place using dolerite ball bearings. Once in the general location, skilled craftsmen would sculpt the stone into the perfect shape.

The precision of the stone on the outside is high, but researchers have found that engineers weren't as careful with the placement as they moved inside.

How were they built?

As for the workforce that built the pyramids? Egyptologists have found huge elaborate cities surrounding the pyramid sites that would've housed entire families, thousands of skilled workers.

Recent research has broken down the idea that slaves were used to construct the structures. There's great evidence that the builders and engineers were highly regarded and respected in Egyptian society.

The pyramids are perhaps the most famous engineering project in all of history. While their scale and complexity may allude to more supernatural origins, there's clear evidence that they were created with skilled work. After all, that's what good engineering does, it takes what's thought to be impossible into reality...

This article was written by Trevor English and first appeard in Interesting Engineering.