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Explosions heard 'round the world

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From North Korean nuclear tests to home-grown Mentos-n-Coke cocktails, if there's one thing our world has plenty of these days, it's explosions. Despite the frequency of modern explosions, however, there are a few historical booms which blow away the competition -- pun intended -- and are remembered today not only for their awesome destructive force, but for being audible many hundreds, if not thousands, of miles away.

The Tunguska Event
The cause of this famous 1908 explosion in Siberia is still contested by some -- everything from alien spacecraft to long-distance energy transmission experiments by Nikola Tesla gone wrong have been posited as its cause -- though most experts believe the culprit was a meteor, which exploded while it was still about six miles above a remote portion of Siberian forest. The blast released 15 megatons of energy—about a thousand times that of the atomic bomb dropped on Hiroshima—and flattened 770 square miles (2,000 square kilometers) of forest. The shock wave broke windows and knocked people off their feet hundreds of miles away, and according to the 1966 Guinness Book, due to the rotation of the Earth, if the meteor had fallen just four and a half hours later it would've wiped the city of St. Petersburg from the map. And in semi-breaking news, scientists think they may have just found the meteorite's impact crater -- some 99 years later.

krakatoa.jpgKrakatoa
Certainly the biggest bang in recent history, the 1893 volcanic explosion on the Indonesian island of Krakatoa rocked the Southern hemisphere, sending 120-foot tidal waves crashing into nearby Java and Sumatra, smoke and debris into the atmosphere in such prodigious quantities that it caused global cooling of about four degrees over the next year, and could be heard from as far away as Perth, Australia (1,930 miles) and the island of Rodrigues near Mauritius (a stunning 3,000 miles distant). And as long as we're comparing explosions to Hiroshima, Krakatoa's force was about 1,000,000 times that of the famed nuke. What's more, all that atmospheric debris made for some dramatically blood-red sunsets 'round the world, which apparently inspired the apocalyptic sky in Munch's The Scream.

Mount Tambora
It seems no one can throw an eruption like Indonesia, also the site of the devastating 1815 eruption of Mount Tambora. The deadliest eruption ever recorded (it probably claimed some 92,000 victims), it ejected so much light-blocking debris into the atmosphere that 1816 was known as "The Year Without a Summer." Indeed, the crop failures and livestock deaths that resulted in much of the Northern hemisphere caused the worst famine of the 19th century -- all thanks to one big explosion. Though more destructive, it doesn't seem to have been as loud as Krakatoa (it was heard a mere 1,200 miles away on Sumatra), though that's still pretty darn loud. In 2004, archaeologists discovered extensive, Pompeii-like remains beneath deep pockets of eruption deposit, including victims, homes and items undisturbed in the positions they had held since the morning they were buried.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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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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iStock
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Why Your iPhone Doesn't Always Show You the 'Decline Call' Button
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iStock

When you get an incoming call to your iPhone, the options that light up your screen aren't always the same. Sometimes you have the option to decline a call, and sometimes you only see a slider that allows you to answer, without an option to send the caller straight to voicemail. Why the difference?

A while back, Business Insider tracked down the answer to this conundrum of modern communication, and the answer turns out to be fairly simple.

If you get a call while your phone is locked, you’ll see the "slide to answer" button. In order to decline the call, you have to double-tap the power button on the top of the phone.

If your phone is unlocked, however, the screen that appears during an incoming call is different. You’ll see the two buttons, "accept" or "decline."

Either way, you get the options to set a reminder to call that person back or to immediately send them a text message. ("Dad, stop calling me at work, it’s 9 a.m.!")

[h/t Business Insider]

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