Mad About Science: The Lighthouse of Alexandria

By Brenden Bobby
Reader Columnist

We live in a time of architectural wonder — so much wonder that even the most triumphant structures ever built by human hands just seem a little bland. It’s important to remember that the true marvel of the wonders of the ancient world wasn’t their size, or even the amount of time they survived — it’s how they were built by people that lacked the kind of technology we have today. The pyramids of Giza might not be as tall as Burj Khalifa, but the ancient Egyptians didn’t have the benefit of advanced metallurgy to reinforce their structures or gasoline-powered vehicles to transport hundreds of tons of stone blocks.

Among one of the most impressive of the ancient wonders of the world was the Lighthouse of Alexandria. It was erected sometime between 284 BCE and 246 BCE on the island of Pharos, in the port of Alexandria, Egypt. Pharos was connected to Alexandria by an artificial land bridge called a mole that stretched nearly a mile, which is an architectural wonder in its own right.

A rendering of what the Lighthouse of Alexandria might’ve looked like. Courtesy Wikipedia.

The lighthouse itself was built from cut stone and stood more than 330 feet tall. Imagine the difficulty of transporting massive stone blocks to an island without the aid of a powered vehicle. There’s only so much weight a wooden barge can hold before it loses buoyancy and sinks to the bottom of the sea, and transporting them across the mole would be a hugely treacherous endeavor.

Additionally, the difficulty of cutting untold thousands of stone blocks to a uniform specification in an age before computers — or, in most cases, standard methods of measurement — would have been a nearly impossible task. How many people do you know that are capable of slapping together a perfect birdhouse without a single measuring tool? Imagine trying to do that for a 330-foot-tall structure, and building that structure to last more than a thousand years.

The lighthouse was constructed in three phases, with a large cubic base that made up about half the structure, with a center core that tapered into an octagon and, finally, a conical top. Anyone who has played Minecraft knows the difficulty of changing the shape of your structure partway through, but creating rounded or conical structures out of square or rectangular blocks is especially challenging and a true testament to the mathematical genius of the lighthouse’s architects. 

Interestingly, Euclidean geometry wouldn’t have been developed for 20 to 60 years after the construction of the lighthouse, and Pi wouldn’t be known to the world until 1706 — almost 2,000 years after the lighthouse’s construction.

The architects of the lighthouse didn’t have calculators, they likely used a primitive form of the abacus, or in some cases just a collection of pebbles when the required calculations became too complex to perform in their heads. I need a graphing calculator to figure out how much damage my seventh-level Oathbreaker Paladin does to a young silver dragon; you won’t catch me building any wonders of the world using my fingers, toes and some rocks any time soon.

I bet you’re wondering what it must have cost to build a structure like that, especially with today’s housing prices. Shockingly, it translated to a lot less than you’d think. The price was recorded to be somewhere along the lines of 800 talents of silver. Depending on the source, a talent was believed to be somewhere between 75 and 100 pounds, which means King Ptolemy I spent about 60,000 pounds of silver to have the lighthouse constructed. Based on today’s silver prices, that cost would be around $23.7 million. While that seems like a large amount of money, that would only buy you about six lakefront houses on Lake Pend Oreille today. To further put that into perspective, the Empire State Building cost a cool $41 million to construct — though when accounting inflation, that would equate to more than $670 million today.

All things considered, paying just under $24 mil for a structure that stood for more than a thousand years seems like a bargain.

Unfortunately, the lighthouse did fall. A number of earthquakes weakened the structure until it suffered a major collapse in 956 CE. In 1323, an earthquake of at least 5.9 magnitude struck and collapsed the rest of the structure, sending most of it to the bottom of the sea. What remained was reclaimed and rebuilt into a medieval fort by the Egyptian sultan, Qaitbay, in 1480.

Archaeologists would find the ruins of the lighthouse after an underwater dive in 1994. Stone blocks weighing upwards of 60 tons — as well as towering statues of sphinxes and King Ptolemy and his wife, Arsinoe — were discovered beneath the waves, prompting the Egyptian government to declare the site an underwater park where, to this day, divers can go to view these historical artifacts.

Are you looking for more information about the ancient wonders of the world? Go check out the library. The best way to support the library is by checking out materials — this helps the staff make informed decisions on how to expand the collection and also guarantees the library gets the vital funding it needs to function. And don’t forget to get out and vote in the May 18 election for the board of trustees.

Stay curious, 7B.