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The Last Time a (Really Big) Meteor Hit Russia

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Wikimedia Commons

In late 1908, the scientific community in St. Petersburg and Moscow was galvanized by vague reports filtering out of Siberia, telling of a gigantic, mysterious explosion that summer that had been witnessed only by a handful of native Evenki tribesmen and Russian settlers.

According to eyewitness reports gathered later by Leonid Kulik, at 7:17 am on June 30, 1908, a column of bright blue light became visible in the sky above central Siberia, followed by a huge explosion near Tunguska, a remote region located in the taiga (pine forest) northwest of Lake Baikal.

The explosion rocked the earth, leveled gigantic swaths of forest, and filled the sky with blinding light, according to one Evenki native, who later remembered: “Then I saw a wonder: trees were falling, the branches were on fire, it became mighty bright, how can I say this, as if there was a second sun, my eyes were hurting, I even closed them.” A Russian settler reported that the explosion blew out windows in buildings up to 40 miles away from the impact, accompanied by intense heat: “At that moment I became so hot that I couldn't bear it, as if my shirt was on fire… hot wind raced between the houses, like from cannons…” The explosion clearly occurred some distance above the ground, with one eyewitness recalling that “the sky split in two and fire appeared high and wide over the forest.”

The effects of the Tunguska Event were breathtaking: the explosion, measuring between 10 and 20 megatons (somewhere between 435 and 870 times the force of the Nagasaki bomb), leveled approximately 80 million trees over an area of 800 square miles, or around half a million acres. No surprise, the simple peasant folk who witnessed it assumed the worst, with one newspaper reporting that “women cried, thinking it was the end of the world.” Later, particulate matter in the atmosphere produced stunning sunsets around the world.

It’s still not clear what caused the Tunguska Event, but based on the eyewitness reports and butterfly-shaped blast pattern, most scientists agree it must have resulted from a meteor or comet exploding about six miles above the ground. The latest theory suggests the object measured around 100 feet across and weighed over 600,000 tons; that’s about three times the size of the world’s largest ocean liners, which weigh in at around 225,000 tons. Interestingly, many eyewitnesses described not just one but a series of explosions, raising the possibility that the event was caused by a string of meteors or parts of a disintegrating comet hitting the earth in succession.

However scientific expeditions led by Kulik beginning in 1921 were unable to recover any fragments of the meteor or comet, and subsequent investigations (including an Italian mission which may have found a crater caused by the explosion in 2007) have also come up empty-handed. Predictably, this has given rise to all sorts of bizarre conspiracy theories, including, yes, an extraterrestrial visitation. Why aliens would want to destroy a remote part of Siberia, and what they have against pine trees, remains unclear.

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iStock // Ekaterina Minaeva
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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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May 23, 2017
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