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In Space, Can Anyone Hear You Scream?

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"In Space, No One Can Hear You Scream." That was the tagline for the movie Alien, Ridley Scott's 1979 sci-fi/horror masterpiece. Released two years earlier, Star Wars allowed us to hear plenty of things in space, like the whine of TIE fighter engines and the explosion of the Death Star.

So which movie is right? How does sound work in space?

Here on Earth, sound travels as mechanical waves transmitted through a solid, liquid or gas medium (like the air in a room, the water in a pool, or the walls in an apartment building). Pluck a guitar string and it vibrates. The vibration of the string pushes against the molecules of air around the string. Those air molecules, in turn, push against other air molecules, which push against still others, creating oscillations of pressure in the air: a sound wave.

Outer space (which, for our purposes here, we will define as the universe beyond Earth's atmosphere and between planets and other stellar bodies) makes a pretty terrible medium for mechanical waves. It's a vacuum, but not a perfect one. Sound can travel through it, but not very effectively. There's plenty of matter in space "“- stars, planets, asteroids, galaxies, cosmic dust, elemental atoms, etc. "“- and it's all separated by vast distances. Even at the densest parts, there's only a few hydrogen and helium atoms in a cubic meter. If you plucked a guitar string in outer space, it would still vibrate and scraps of matter like cosmic dust and gases might be able to propagate sound waves if you got enough of the matter together, but the sound be too weak for our not-that-sensitive ears to hear.

alien-screamSo, Alien has it right; while it's not strictly true that sound waves can't travel through space, it is true that humans would not be able to hear those sounds. Scream all you want, no one is hear you. There are some loopholes in what we'll call "Ridley's Law," though. Among the things you could hear in space are:


"¢ Anyone talking to you via radio. Radio waves can travel through space because they're electromagnetic, not mechanical, and can travel through a vacuum. Once the radio in your spaceship or spacesuit receives the signal, it converts the signal into sound, which travels through the air in your ship or helmet to your ear.


"¢ A bump on the head. If you're floating in space wearing a spacesuit and you hit your head on something (your ship, an asteroid, whatever), the sound waves resulting from the vibration of your helmet and the object you bumped would be able to travel through your helmet and the air inside it to your ear.

If you've got the right tools, you could also see sounds of a black hole. In 2002, NASA's Chandra X-ray Observatory detected a B-flat note coming from a black hole in the Perseus Galaxy Cluster, some 250 million light-years away. The note is 57 octaves below a piano's Middle C. That's far too low for us to hear. NASA didn't hear the note, either -- they saw it as ripples in the cosmic gas surrounding the hole, caused by the squeezing and heating of the gas by the gravitational pressure of the clump of galaxies packed together in the cluste. They determined the pitch by calculating how far apart the ripples were, and how fast they traveled.

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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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Nick Briggs/Comic Relief
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What Happened to Jamie and Aurelia From Love Actually?
May 26, 2017
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Nick Briggs/Comic Relief

Fans of the romantic-comedy Love Actually recently got a bonus reunion in the form of Red Nose Day Actually, a short charity special that gave audiences a peek at where their favorite characters ended up almost 15 years later.

One of the most improbable pairings from the original film was between Jamie (Colin Firth) and Aurelia (Lúcia Moniz), who fell in love despite almost no shared vocabulary. Jamie is English, and Aurelia is Portuguese, and they know just enough of each other’s native tongues for Jamie to propose and Aurelia to accept.

A decade and a half on, they have both improved their knowledge of each other’s languages—if not perfectly, in Jamie’s case. But apparently, their love is much stronger than his grasp on Portuguese grammar, because they’ve got three bilingual kids and another on the way. (And still enjoy having important romantic moments in the car.)

In 2015, Love Actually script editor Emma Freud revealed via Twitter what happened between Karen and Harry (Emma Thompson and Alan Rickman, who passed away last year). Most of the other couples get happy endings in the short—even if Hugh Grant's character hasn't gotten any better at dancing.

[h/t TV Guide]

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