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4 Terrifying Theories in Astronomy

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This article was written by Jay M. Pasachoff, Professor of Astronomy at Williams College, and originally appeared in mental_floss magazine.

Galileo may have been threatened with the rack during the Inquisition almost 400 years ago, but—relatively speaking—that was hardly terrifying. Whether the Earth went around the Sun (as Copernicus, Galileo and Newton thought) or vice versa (in the old model of Ptolemy or Aristotle), Galileo's Universe was still a placid place. But these days, astronomers are facing threats so bone chilling, they make the rack look like a simple walk on the moon. Here are some of the things astronomers worry about, and some things you may want to start worrying about, too.

1) Asteroid Extinction

Most of us humans think we're the kings and queens of the Earth, lording over our dominions with our big brains. But so did the dinosaurs, up until about 65 million years ago when, one day, a small asteroid came their way, colliding with the Earth and creating a cloud of dust across the planet. From the dust and the cooling temperatures that resulted, thousands of species died. The dinosaurs joined in this mass extinction, and any day now, we could be in for a mass extinction of our own.

Evidence of future asteroid collisions with Earth can be found by analyzing past collisions like the one that ended the dinosaur age. So what do we know about that collision so long ago? Evidence of the collision began emerging when California scientist Luis Alvarez and his son Walter discovered the element iridium in a layer of segment all around the planet. The layer was known from radioactive dating to be 65 million years old, and, when coupled with the fact that asteroids are sometimes known to be rich in that metal, the idea of a collision became plausible.

dino_chicxulub.jpgVerification of the theory came when the actual crater created by the asteroid was located in the ocean off the Yucatan peninsula of Mexico. Known as Chicxulub, the crater is now covered with sediment, but geologists and space mapping have traced out its structure, leading to the discovery of giant rings hundreds of miles across the Earth's surface.

Based on this evidence, scientists estimated that the asteroid that hit Earth during the dinosaur age may have been about ten kilometers (about six miles) across. And that's bad news because asteroids or meteorites that size are thought to hit the Earth every 100 million years or so. Thus, we may be due. Several space projects are now scanning the skies to detect asteroids that may be on a collision course with Earth. The hope is that if there are any giant, apocalypse-capable asteroids heading for us, they may now be in an orbit around the Sun, and we will have many years advance notice to do something about it. There are about 1,000 near-Earth asteroids greater than 1 km in diameter (still a civilization-threatening size), and astronomers calculate that there is a one percent chance of a collision with one of them each thousand years. So it may not be time to get to work on that fallout shelter you designed in the 1940s, but it's not time to throw out the blueprints, either.

2) Here Comes the Sun "¦ Seriously This Time

The Sun may seem hot on a summer's day, but you ain't seen nothing' yet. That's right: The Sun will get even hotter in the future. Today, the surface of the Sun is about 6,000 degrees Celsius (about 10,000 degrees Fahrenheit). The problem is, the Sun is only a middle-aged star right now, and stars (unlike people) get hotter with old age.

the-sun.jpgScientists determine the intensity of the Sun's heat by measuring its light in two different ways. The first is to look at the Sun's color: The Sun gives off mostly yellow-green light, with lesser amounts of red light at longer wavelengths and lesser amounts of blue light at shorter wavelengths. Hotter stars give off even more blue light relative to yellow-green, while cooler stars give off relatively more red light. The second method is for astronomers to break down the Sun's light into its color spectrum. Astronomers use spectrographs to spread the color spectrum out, allowing them to see specific colors that are absent or relatively dark. These darkened colors tell astronomers the Sun's temperature.

But what will happen in the future? The Sun is now about halfway through its 10 billion-year lifetime. In a few billion years the outer parts of the Sun will begin to swell, making the Earth hotter. Eventually, the oceans will boil, making human survival, much less a dip in the sea, impossible. (Of course, by then we may be able to get onto rockets and go farther out into the solar system or even to neighboring ones.) After about 5 billion years, the Sun will swell so much that it will become a "red giant," with its surface extending beyond where Mercury's orbit is today. By then the Earth will be roasted, and nobody will be around to see the Sun give off its outer layers, which is too bad because it will actually be quite beautiful; the layers will puff away to make a colorful planetary nebula like the famous Ring Nebula. And nobody will be around on Earth when the remaining core of the Sun shrinks to become a superhot white dwarf.

Actually, even now some parts of the Sun are much hotter than 6,000 degrees. The Sun's center is about 15 million degrees, and the Sun's outer layer—the solar corona that we see at total eclipses—is about 2 million degrees (4 million degrees Fahrenheit). But that high temperature merely tells us that the particles (electrons, protons, etc.) in the corona are moving around very quickly. Luckily, however, there are not enough of them to hold a dangerous amount of energy.

3) Exploding Stars

Our Sun may broil our home in a few billion years, but there are some other stars that could explode, or implode—to be exact—any day. At the core of a star, fusion transforms hydrogen into helium and a bit of helium into carbon. Sounds harmless enough, right? Normally, it is. At the Sun's core, for example, the pressure from the radiation coming out from the nuclear fusion balances gravity, and all is safe and good.

exploding_stars.jpgIn a more massive star, however—one with five times the Sun's mass or more—the inside becomes so hot that the core's carbon fuses into heavier elements like oxygen and magnesium. The creation of these heavier elements generates a great deal of energy, and, eventually, the elements turn into iron, when all hell breaks loose. As fusion continues in the star's core, iron takes in energy instead of giving off energy. So once iron accumulates in the core, the energy is sucked out of the center of the star and the star collapses. Within seconds, the outer layers fall in from millions of miles up, and the star becomes a supernova.

Astronomers believe that a supernova implodes in our galaxy every 100 years or so, but we haven't seen any since the great astronomers Tycho Brahe (in 1572) and Johannes Kepler (in 1604) saw and wrote about them. This may be because most supernovae are believed to be on the far side of the galaxy, hidden from us by the dust in our galaxy's center. The nearest supernova we know of today recently formed in the Large Magellanic Cloud, one of Milky Way's satellite galaxies that is closer to us on Earth than some parts of our own galaxy. The supernova exploded in 1987 and reached a brightness sufficient enough to be seen with the naked eye. It then faded, but, today, the matter ejected from its core is hitting matter ejected long ago, and it appears that the supernova is brightening again. In fact, we may soon be able to see it without telescopes again.

So far, these supernovae have been safely far away. But a supernova too close to us—as in anywhere in our part of the galaxy—could wipe us all out with its x-rays, gamma-rays and other particles. And actually, the possibility is quite realistic. Many scientists have had their telescopes focused on one object in particular that looks like a massive star, and, over the last 100 years or so, it has brightened and changed substantially. Maybe it is a supernova on the verge of going off. Or maybe it has already exploded, its radiation currently en route and capable of reaching us any day now!

4) Accelerating Universe

As the astronomer Edwin Hubble figured out in the 1920s, our Universe is constantly expanding. Back then, Hubble measured changes in the sky by sitting out all night in the cold using a telescope to take photographs with exposures up to eight hours long. His giant telescope focused its light onto a tiny piece of film that was coating a glass plate. The light from the sky created a spectrum, which showed all the patterns of colors in the sky and shifts in those colors. The evidence from his photographs showed him that the farther galaxies had their spectra shifted more, helping him to deduce, in a leap of genius, that the Universe was expanding uniformly.


Since Hubble's early work, the expansion of the Universe has been a cornerstone of cosmology. When NASA launched a space telescope in 1990, they named it after him, since studying cosmology and the expansion of the Universe was a major part of its mission. Now, NASA has named its successor (to be launched in 2010) after James Webb, who was the Administrator of NASA. (Whether or not it is a good thing that its naming has moved from scientists to bureaucrats is yet undetermined.)

In the last few years, telescopes have gotten bigger and more powerful. And, by 1998, a related phenomenon had been discovered, and it surprised everyone. It turns out that the most distant galaxies weren't going away at the rate that astronomers had expected. They were going away even faster, which made them look fainter than expected. The phenomenon is known as the "accelerating universe."

Do you like your future hot and bright, or do you prefer it cold and dark? The accelerating Universe theory seems to tell us that the latter is what will happen. Some had thought the Universe would eventually stop its expansion and start contracting, but it looks now as though the Universe will expand forever, with galaxies just getting farther and farther apart, disappearing from our view. Eventually, the stars will die and reach their final stages as white dwarfs, neutron stars or black holes. After 50 billion years or so, the Universe will be just a dying vestige of its current magnificence.

It's a good thing that all of recorded history—say 5000 years—is only one ten-millionth of the time until 50 billion years have passed. It will take a trillion times a 50-year adult lifetime until we reach that distant stage of the Universe, so perhaps we shouldn't worry so much after all.

Previously on mental_floss:

The Moon Disaster That Never Happened
Six Cool Plants We'd Find A Way To Kill
People Ferment The Darndest Things
Disgusting Flavors We Never Got A Chance To Love
The Analogist: Party-Crashing Soviet Spacecrafts

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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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Sponsor Content: BarkBox
8 Common Dog Behaviors, Decoded
May 25, 2017
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Dogs are a lot more complicated than we give them credit for. As a result, sometimes things get lost in translation. We’ve yet to invent a dog-to-English translator, but there are certain behaviors you can learn to read in order to better understand what your dog is trying to tell you. The more tuned-in you are to your dog’s emotions, the better you’ll be able to respond—whether that means giving her some space or welcoming a wet, slobbery kiss. 

1. What you’ll see: Your dog is standing with his legs and body relaxed and tail low. His ears are up, but not pointed forward. His mouth is slightly open, he’s panting lightly, and his tongue is loose. His eyes? Soft or maybe slightly squinty from getting his smile on.

What it means: “Hey there, friend!” Your pup is in a calm, relaxed state. He’s open to mingling, which means you can feel comfortable letting friends say hi.

2. What you’ll see: Your dog is standing with her body leaning forward. Her ears are erect and angled forward—or have at least perked up if they’re floppy—and her mouth is closed. Her tail might be sticking out horizontally or sticking straight up and wagging slightly.

What it means: “Hark! Who goes there?!” Something caught your pup’s attention and now she’s on high alert, trying to discern whether or not the person, animal, or situation is a threat. She’ll likely stay on guard until she feels safe or becomes distracted.

3. What you’ll see: Your dog is standing, leaning slightly forward. His body and legs are tense, and his hackles—those hairs along his back and neck—are raised. His tail is stiff and twitching, not swooping playfully. His mouth is open, teeth are exposed, and he may be snarling, snapping, or barking excessively.

What it means: “Don’t mess with me!” This dog is asserting his social dominance and letting others know that he might attack if they don’t defer accordingly. A dog in this stance could be either offensively aggressive or defensively aggressive. If you encounter a dog in this state, play it safe and back away slowly without making eye contact.

4. What you’ll see: As another dog approaches, your dog lies down on his back with his tail tucked in between his legs. His paws are tucked in too, his ears are flat, and he isn’t making direct eye contact with the other dog standing over him.

What it means: “I come in peace!” Your pooch is displaying signs of submission to a more dominant dog, conveying total surrender to avoid physical confrontation. Other, less obvious, signs of submission include ears that are flattened back against the head, an avoidance of eye contact, a tongue flick, and bared teeth. Yup—a dog might bare his teeth while still being submissive, but they’ll likely be clenched together, the lips opened horizontally rather than curled up to show the front canines. A submissive dog will also slink backward or inward rather than forward, which would indicate more aggressive behavior.

5. What you’ll see: Your dog is crouching with her back hunched, tail tucked, and the corner of her mouth pulled back with lips slightly curled. Her shoulders, or hackles, are raised and her ears are flattened. She’s avoiding eye contact.

What it means: “I’m scared, but will fight you if I have to.” This dog’s fight or flight instincts have been activated. It’s best to keep your distance from a dog in this emotional state because she could attack if she feels cornered.

6. What you’ll see: You’re staring at your dog, holding eye contact. Your dog looks away from you, tentatively looks back, then looks away again. After some time, he licks his chops and yawns.

What it means: “I don’t know what’s going on and it’s weirding me out.” Your dog doesn’t know what to make of the situation, but rather than nipping or barking, he’ll stick to behaviors he knows are OK, like yawning, licking his chops, or shaking as if he’s wet. You’ll want to intervene by removing whatever it is causing him discomfort—such as an overly grabby child—and giving him some space to relax.

7. What you’ll see: Your dog has her front paws bent and lowered onto the ground with her rear in the air. Her body is relaxed, loose, and wiggly, and her tail is up and wagging from side to side. She might also let out a high-pitched or impatient bark.

What it means: “What’s the hold up? Let’s play!” This classic stance, known to dog trainers and behaviorists as “the play bow,” is a sign she’s ready to let the good times roll. Get ready for a round of fetch or tug of war, or for a good long outing at the dog park.

8. What you’ll see: You’ve just gotten home from work and your dog rushes over. He can’t stop wiggling his backside, and he may even lower himself into a giant stretch, like he’s doing yoga.

What it means: “OhmygoshImsohappytoseeyou I love you so much you’re my best friend foreverandeverandever!!!!” This one’s easy: Your pup is overjoyed his BFF is back. That big stretch is something dogs don’t pull out for just anyone; they save that for the people they truly love. Show him you feel the same way with a good belly rub and a handful of his favorite treats.

The best way to say “I love you” in dog? A monthly subscription to BarkBox. Your favorite pup will get a package filled with treats, toys, and other good stuff (and in return, you’ll probably get lots of sloppy kisses). Visit BarkBox to learn more.