Obelisks: Enigmatic Ancient Monuments of Engineering
No doubt, obelisks are fantastic and huge, but they all include mysterious scientific purposes. From being the first calculator for the circumference of the Earth to the making and rising processes in construction, obelisks are mystic engineering wonders of the world.
They all are spread all around the world. Most of them stand in the most beautiful squares of the cities and get big attention by tourists. Whenever we get closer to one of them, we’re wondering about exactly the same thing; how they were constructed?
So, how were obelisks erected?
[Image Source: P.R.T.]
Unfortunately, we don’t have any writings from Ancient Egypt that explain it. But the scientists and the historians are saying that The Egyptians might have preferred different construction methods at different times.
[Image Source: MegalithMovers]
Obelisks were probably pulled up artificial ramps, bottom first, with ropes, and lowered onto their bases. So, how was a single block of stone 100 feet high so accurately positioned without breaking? Historical engineers claim that an artificial ditch could have been created, with the obelisk’s base in the middle. People could have filled the ditch with sand, and several men could have pulled ropes from many directions to carefully guide the monument.
Transporting the obelisk
20th January 1881: A 69.5 ft Egyptian obelisk which had graced the entrance to the Temple of the Sun in Heliopolis in 1500 BC and was taken to Alexandria by the Roman Emperor Augustus in 23 BC, is erected in Central park, New York, having been donated as a gift to the city by the Egyptian Khedive. [Image Source: NY History]
This may seem to be a very difficult task to perform but the engineers at the time managed perfectly well without modern machinery or steel cranes.
[Image Source: Debar]
The obelisks were conveniently made at quarries situated on the banks of the Nile. They were then easily transported on the river in specially built ships. They cruised at the flooding days when the river was deeper.
First calculation of the circumference of the earth
[Image Source: Sam Thomson]
Around 250 B.C., a Greek philosopher named Eratosthenes used an obelisk to calculate the circumference of the Earth. He knew that at noon on the Summer Solstice, obelisks in the city of Swenet (modern day Aswan) would cast no shadow because the sun would be directly overhead (or zero degrees up). He also knew that at that very same time in Alexandria, obelisks did cast shadows. Measuring that shadow against the tip of the obelisk, he came to the conclusion that the difference in degrees between Alexandria and Swenet: seven degrees, 14 minutes—one-fiftieth the circumference of a circle. He applied the physical distance between the two cities and concluded that the circumference of the Earth was (in modern units) 40,000 kilometers. This isn’t the correct number, though his methods were perfect: at the time it was impossible to know the precise distance between Alexandria and Swenet.
If we apply Eratosthenes's formula today, we get a number astonishingly close to the actual circumference of the Earth. In fact, even his inexact figure was more precise than the one used by Christopher Columbus 1700 years later. Had he used Eratosthenes’s estimation, Columbus would have known immediately that he hadn’t reached India.
They were really, really hard to build
[Image Source: SunSurfer]
Nobody knows exactly how obelisks were built. Granite is really hard—a 6.5 on the Mohs scale (diamond being a 10)—and to shape it, you need something even harder. The metals available at the time were either too soft (gold, copper, bronze) or too difficult to use for tools (iron’s melting point is 1,538 °C; the Egyptians wouldn’t have iron smelting until 600 B.C.).
[Image Source: WikiMedia]
The Egyptians likely used balls of dolerite to shape the obelisks, which, Gordon notes, would have required “an infinity of human effort.” Hundreds of workers would have each had to pound granite into shape using dolerite balls that weighed up to 12 pounds. This doesn’t even address the issue of how one might move a 100-foot, 400-ton column from the quarry to its destination. While there are many hypotheses, nobody knows precisely how they did it.