Ramps compared, and why it is still debated

The blocks had to go up. A pyramid 146.6 m high needs some way to raise 2.3 million blocks to their places. The most common idea is a ramp, a sloping track of earth, brick or rubble. But no ramp survives beside the Great Pyramid in a form that settles the question, so several ramp designs are proposed. Here you will compare them like an engineer, and see why the honest answer is 'not settled'.

Idea 1: a straight ramp. A single ramp pointing straight at one face. For a gentle slope of 1 in 10 it must be about 146.6 m × 10 ≈ 1.47 km long to reach the top. That is the trouble: a ramp has a volume, and the volume of a long, wide ramp can rival the pyramid itself. A ramp that is 10 m wide and 1.47 km long to the top has a volume of ½ × 1,466 m × 146.6 m × 10 m ≈ 1.1 million m³, about 40 percent of the pyramid. Make it about 24 m wide and the ramp would be as big as the whole pyramid. A steeper ramp is shorter but harder to haul up: at 1 in 3 the length falls to about 440 m, but pulling a 2.5 t sledge on wet sand needs about 24.5 × (0.316 + 0.25 × 0.949) ≈ 13.6 kN, around 34 people at 0.4 kN each, against about 21 on a 1 in 10 slope.

Idea 2: a zigzag ramp that climbs the face of the pyramid in switchbacks. It uses less material, but the turns need space and blocks cannot swing round tight corners easily. Idea 3: an external spiral, a ramp wrapping around the pyramid. It saves material, but it covers the corners, which builders need to see to keep the pyramid's edges straight.

Idea 4: an internal ramp. The French architect Jean-Pierre Houdin proposed (in 2007) that the lower third was built with a straight external ramp, and that above that the blocks were hauled up an internal spiral ramp hidden inside the pyramid. This idea explains some features, but it is a hypothesis. In recent years, scanning with cosmic-ray detectors (the ScanPyramids project) has found unexplained voids inside the pyramid, but what they are is not known, and they do not prove any ramp design.

What evidence do we have?

• Remains of brick-and-rubble ramps survive at some other pyramid sites and temples (for example at Meidum), so ramps were certainly used in Egypt.
• At the Hatnub alabaster quarry in Middle Egypt, archaeologists found a steep ramp with a slope of roughly 20 percent, with rows of post holes on both sides. The post holes may have held posts for ropes that gave extra pulling power on a steep slope, which is a hypothesis. Inscriptions at the site link the work to the reign of Khufu. This shows that steep haulage was possible, but it is a quarry ramp, not a pyramid ramp.
• No single ramp has been proven for the whole pyramid. It is quite possible that several methods were used at different heights.