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Why Are Moths Drawn to Flames?

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Around the world, moths make kamikaze dives into light bulbs and open flames with such regularity that they have their own idiom. What is it about lights that make moths so crazy?


For a long time, scientists blamed the moon. Moths used the moon as a navigational beacon, it was argued, keeping it at a constant angle to their direction of travel in order to fly straight. Light sources used by humans, whether they’re campfires or porch lights, threw a monkey wrench into this system. The moon is far enough away that the angle between it and a traveling moth isn’t going to change much, even after the moth flies a great distance. With a closer light source, though, the angle changes considerably after only a short distance. A moth confusing a light bulb or candle flame for the moon, the hypothesis went, would notice this change and attempt to correct its path by turning toward the light. After just a few course corrections, the moth would set itself into a tightening death spiral towards the light and eventually crash into it, either going down in flames or thwacking its poor little head.

On Second Thought...

Over the years, various holes were poked in this hypothesis. For one—and this is a big one—moths might not even use the moon for navigation.

There isn’t much evidence for it, especially when it comes to the over 50 percent of moths that don't migrate and wouldn’t have much use a celestial navigation aid in their short distance travels.

There’s also the fact that moths don't always circle around lights in a closing spiral like the moon hypothesis assumes. Most of the time, they actually head straight for it. Henry Hsiao, a professor of Biomedical Engineering at the University of North Carolina, has tracked moth flights as the bugs headed toward a light source and found that, most of the time, they fly in a straight line toward the light until they get very close, then veer off and circle at a steady distance.

Hsiao’s observations led him to develop a new hypothesis. He’s unsure what causes the moth to make a beeline to a light, but thinks that the circling behavior at close ranges is caused by a visual distortion common to all sighted creatures called a “Mach band.” The band is the region surrounding a bright light that is perceived as being darker than any other part of the sky. Hsiao thinks that moths hang out in the band because they want the cover of darkness for safety, and wind up circling the light until their flight path takes them away from the it (or causes them to crash into it).

Love Hurts

Another explanation, proposed by U.S. Department of Agriculture entomologists in the 1970s, is that the infrared light spectrum emitted by candle flames contains some of the exact same wavelengths of light given off by female moths' luminescent pheromones. In other words, it’s just male moths that are attracted to flames because they wrongly assume that they’re going to get lucky. This doesn’t explain their attraction to UV light, which doesn’t emit the same light wavelengths as moth pheromones, but it does say something very profound about the lure of love.

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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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