Tonight on PBS: NOVA - Riddles of the Sphinx

So what's the story with the Great Sphinx? Who built it, when, and why? And what happened to its nose? Those are all riddles answered in tonight's episode of NOVA -- but there's much more interesting sphinx trivia in the program. Mark your calendars! It airs tonight, January 19, on PBS. If you miss the broadcast, check the PBS website as the entire program will stream for a limited time online beginning the day after it airs.

Discussed in tonight's NOVA episode: how the Great Sphinx was, for a time, painted in bright colors (primarily red); the controversy over which pharaoh the face represents; why there are additional layers of new stone added around the lower part of the body; why the upper part of the body is so weathered; what tools were used to carve the sphinx; and what it says on the stele sitting between the paws. I'll give you a hint on that last one: it's the story of how Thutmose IV restored the Great Sphinx, after it was buried in the sand. And he was just the first of many to do restoration work on the status; many cultures including the Greeks and Romans had a hand in resurfacing or restoring it over the millennia.

Further trivia of note: Napoleon's soldiers did not shoot off the nose; modern carvers estimate that it took roughly one million man-hours to carve the sphinx (thus, 100 carvers working for three years, plus a massive support staff to constantly repair the soft bronze tools they used); and the fact that some pharaohs were buried with lion bones -- the sphinx as a form is apparently a merging of a pharaoh (as evidenced by the pharaonic headdress) and a lion, a powerful symbolic combination.

I've seen my share of NOVA programs, and I recommend this one for anyone interested in Egyptology, restoration, construction, or watching a couple of gentlemen try to carve a scaled-down sphinx nose out of stone using ancient tools (what they learn: power tools are a whole lot faster).

Further viewing: check out Building Pharaoh's Ship (currently streaming online in its entirety) for more NOVA Egypt goodness.

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

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Name the Author Based on the Character
May 23, 2017
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