CLOSE
Original image
iStock

7 Fascinating Facts About Obelisks

Original image
iStock

The first thing you might not know about obelisks is what they are. If you have ever visited the Washington Monument, however, or walked across the Place de la Concorde in Paris, or seen any rendering of ancient Egypt in its glory, you are very familiar with obelisks: vertical stone columns that taper as they rise, topped by a pyramid. Washington’s Monument and the Fascinating History of the Obelisk, by John Steele Gordon, is an absorbing account of the obelisk’s place in human civilization. Here are seven things revealed by Gordon that you might not know about obelisks.

1. THEY WERE BUILT BY THE ANCIENT EGYPTIANS, THOUGH ONLY A FEW REMAIN IN EGYPT.

The ancient Egyptians placed pairs of obelisks at the entrances of their temples. According to Gordon, the columns were associated with the Egyptian sun god, and perhaps represented rays of light. They were often topped with gold, or a natural gold-and-silver alloy called electrum, in order to catch the first rays of the morning light. Twenty-eight Egyptian obelisks remain standing, though only six of them are in Egypt. The rest are scattered across the globe, either gifts from the Egyptian government or plunder by foreign invaders.

2. AN OBELISK WAS USED IN THE FIRST CALCULATION OF THE CIRCUMFERENCE OF THE EARTH.

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.

3. TRUE OBELISKS ARE MADE OF A SINGLE PIECE OF STONE.

True obelisks as conceived by the ancient Egyptians are “monolithic,” or made from a single piece of stone. (The literal translation of monolith—a Greek word—is “one stone.” On that note, the word “obelisk” is also Greek, derived from obeliskos, or skewer. An ancient Egyptian would have called an obelisk a tekhen.) The obelisk at the center of Place de la Concorde, for example, is monolithic. It is 3300 years old and once marked the entrance to the Temple of Thebes in Egypt. So difficult is the feat of building a monolithic obelisk that Pharaoh Hatshepsut had inscribed at the base of one of her obelisks the proud declaration: “without seam, without joining together.”

4. THEY WERE REALLY, REALLY HARD TO BUILD.

Nobody knows exactly why obelisks were built, or even how. 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.).

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.

5. AN OBELISK HELPED ARCHAEOLOGISTS TRANSLATE HIEROGLYPHICS.

Until the 19th century, hieroglyphics were thought to be untranslatable—mystical symbols with no coherent message beneath. Jean-François Champollion, a French Egyptologist and linguist, thought differently, and made it his life’s purpose to figure them out. His first success came from the Rosetta Stone, from which he divined the name “Ptolemy” from the symbols. In 1819, “Ptolemy” was also discovered written on an obelisk which had just been brought back to England—the Philae obelisk. The “p,” “o,” and “l” on the obelisk also featured elsewhere on it, in the perfect spots to spell the name “Cleopatra.” (Not that Cleopatra; the much earlier Queen Cleopatra IX of Ptolemy.) With those clues, and using this obelisk, Champollion managed to crack the mysterious code of hieroglyphics, translating their words and thus unlocking the secrets of ancient Egypt. (Almost 200 years later, the European Space Agency’s mission to land a spacecraft on a comet commemorated these events; the spacecraft is named Rosetta. The lander is named Philae.)

6. THE OLDEST REMAINING OBELISKS ARE AS OLD AS RECORDED HUMAN HISTORY.

The oldest obelisks are almost impossibly old—ancient even by the standards of antiquity. Seaton Schroeder, an engineer who helped bring Cleopatra’s Needle to Central Park, called it a “might monument of hoary antiquity,” and commented eloquently, “From the carvings on its face we read of an age anterior to most events recorded in ancient history; Troy had not fallen, Homer was not born, Solomon’s temple was not built; and Rome arose, conquered the world, and passed into history during the time that this austere chronicle of silent ages has braved the elements.”

7. THE TALLEST OBELISK IN THE WORLD IS THE WASHINGTON MONUMENT.

First conceived in 1832, the Washington Monument took decades to build. It is, by law, the tallest structure in the District of Columbia, and is twice as tall as any other obelisk in the world. Gordon notes that it stands unique among memorials in Washington. Whereas people visit memorials to Lincoln and Jefferson (among others) to see giant statues of the men they commemorate, the highlight of the Washington Monument is the monument itself. The statue of Washington inside receives little notice. As Gordon writes in Washington’s Monument, “The obelisk, silent as only stone can be, nonetheless seems to say as nothing else can, ‘Here is something significant.’”

Original image
iStock // Ekaterina Minaeva
technology
arrow
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
Original image
iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

Original image
quiz
arrow
Name the Author Based on the Character
May 23, 2017
Original image
SECTIONS
BIG QUESTIONS
BIG QUESTIONS
WEATHER WATCH
BE THE CHANGE
JOB SECRETS
QUIZZES
WORLD WAR 1
SMART SHOPPING
STONES, BONES, & WRECKS
#TBT
THE PRESIDENTS
WORDS
RETROBITUARIES