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The aurora borealis in northern Norway. Photo by AP Photo / Scanpix Norway, Rune Stoltz Bertinussen

Our photo gallery of the most stunning images from the recent northern lights show.

Precious few people around the world have ever had the chance to witness the remarkable phenomenon known as the aurora borealis, or northern lights. The collision of magnetically charged solar particles with the earth’s magnetosphere produces dancing waves of florescent green and deep blue that appear to wave across the sky, but under normal conditions, the lights can been seen only in far northern latitudes. Even then, the aurora borealis is unpredictable in occurrence and can be difficult to spot.

Recent storms on the surface of the sun, though, have produced levels of solar particles headed towards the earth not seen for a decade—and dazzling northern lights. Skygazers report that, over the past week, remarkably intense displays have appeared in skies in Scandinavia and Northern England. Scientists predict that recent surges are just a small taste of what’s to come over the next year or so, as the cycle of solar activity is expected to peak in 2013 and 2014.

A dragon statue in Ljubljana, Slovenia. Photo courtesy Wikimedia Commons.

Around the world, people are celebrating the Chinese New Year and the start to the Year of the Dragon. This got us wondering: Where did the myth of the dragon come from in the first place? Scholars say that belief in dragons probably evolved independently in both Europe and China, and perhaps in the Americas and Australia as well. How could this happen? Many have speculated about which real-life animals inspired the first legends. Here’s our run-down of the likeliest suspects.

Dinosaurs. Ancient people may have discovered dinosaur fossils and understandably misinterpreted them as the remains of dragons. Chang Qu, a Chinese historian from the 4th century B.C., mislabeled such a fossil in what is now Sichuan Province. Take a look at a fossilized stegosaurus, for example, and you might see why: The giant beasts averaged 30 feet in length, were typically 14 feet tall and were covered in armored plates and spikes for defense.

The Nile Crocodile. Native to sub-Saharan Africa, Nile crocodiles may have had a more extensive range in ancient times, perhaps inspiring European dragon legends by swimming across the Mediterranean to Italy or Greece. They are among the largest of all crocodile species, with mature individuals reaching up to 18 feet in length—and unlike most others, they are capable of a movement called the “high walk,” in which the trunk is elevated off the ground. A giant, lumbering croc? Might be easy to mistake for a dragon.

The Goanna. Australia is home to a number of species of monitor lizards, also referred to as Goannas. The large, predatory animals have razor-sharp teeth and claws, and they are important figures in traditional Aboriginal folklore. Recent studies even indicate that Goannas may produce venom that causes bite victims’ wounds to develop infections after an attack. At least in Australia, these creatures may be responsible for the dragon myth.

Whales. Others argue that the discovery of megafauna such as whales prompted stories of dragons. Ancient humans encountering whale bones would have no way of knowing that the animals were sea-based, and the idea of such gargantuan creatures might well have led people to assume that whales were predatory. Because live whales spend up to 90 percent of their time underwater, they were poorly understood for most of human history.

The Human Brain. The most fascinating explanation involves an unexpected animal: the human. In his book An Instinct for Dragons, anthropologist David E. Jones argues that belief in dragons is so widespread among ancient cultures because evolution embedded an innate fear of predators in the human mind. Just as monkeys have been shown to exhibit a fear of snakes and large cats, Jones hypothesizes that the trait of fearing large predators—such as pythons, birds of prey and elephants—has been selected for in hominids. In more recent times, he argues, these universal fears have been frequently combined in folklore and created the myth of the dragon.

Last summer, on July 6, solar scientist Karel Schrijver spotted something unusual. Looking at a coronagraph—an image created by blocking out the center of the sun, revealing only the corona, the area near its surface—he saw a bright comet, identified as C/2011 N3, descending into the solar atmoshpere. When he searched for the comet on images produced by the Solar Dynamic Observatory (SDO), a solar observation satellite that orbits the earth, he realized he was seeing something unprecedented. For the very first time, the death of a comet crashing into the sun had been caught on camera.

A new paper, published by Schrivjer and a team of scientists today in Science, details the find and what it means for astronomy. Comets dive into the sun frequently, but previous ones had been too small and dim to be seen against the glaring backdrop of the sun. But this comet, an ultra-bright one from a group known as the Kreutz comets, was caught by SDO imaging equipment plunging to its death. Over the course of 20 minutes, it clearly appears descending across the sun before disappearing into its surface. Space.com notes:

“It was very surprising to see this comet at all,” Karel Schrijver, an astrophysicist at Lockheed Martin Advanced Technology Center in Palo Alto, Calif., told SPACE.com. “We may think that an object of some 60,000 metric tons and some 50 meters [164 feet] across is large and heavy, but if you compare it to the sun, which can easily hold a million Earths, it is astonishing that such a small object glows brightly enough to be seen.”

The find, it turns out, is more than merely interesting: It has helped the scientists develop a new method for calculating the size of comets from afar. Using two figures—the amount of time it took the comet to evaporate and the distance over the sun it traveled while doing so—the team figured out its size and speed.

The C/2011 N3 comet is caught on a coronagraph, an image that blocks out the sun to reveal its corona. Image courtesy of NASA Solar and Heliospheric Observatory

“It was moving along at almost 400 miles per second through the intense heat of the sun—and was literally being evaporated away,” said Schrijver, the lead author of the paper. As the Bad Astronomy blog points out, that speed means it would have crossed the width of the United States in about 8 seconds.

The researchers also estimate that the comet came within 62,000 miles of the sun’s surface before evaporating, and was 70,000 tons in size (about the weight of an aircraft carrier), trailed by a tail 10,000 miles in length.

Some aspects of the discovery, though, are still confusing for the scientists. Most surprising is the fact that we could see the comet at all. Because objects passing in front of the sun absorb light, the comet should have appeared as a dim spot rather than a bright one. Solving this mystery, along with others, might help reveal information about the composition of comets, the sun’s corona and perhaps even the origins of the solar system. Scientists will continue to look to the sun—and scrutinize the data—for answers.

Perceptions of wealth are often more complicated than just net worth, a new study indicates. Photo courtesy of flickr user AMagill

A recent thread on the urban parenting site Urbanbaby.com asked a simple pair of questions: What is your household income, and how rich do you feel? The resulting contradictions of income and perceived wealth drew widespread remark—and some scorn. One commenter, from New York City’s Upper East Side, makes $350,000 per year and feels “so, so, so poor.” Another earns $1.2 million and feels upper-middle class, while a third, with an income in the $180,000 range in the D.C. suburbs, feels rich.

How is this all possible? Everyone knows the old platitude “beauty is in the eye of the beholder.” A recent psychological study indicates that wealth is just the same. A new paper, published in the January issue of Psychological Science by Princeton researcher Abigail Sussman, demonstrates that total net worth is not the only thing that influences perceptions of wealth, whether for ourselves or others.

If you were asked to consider two individuals—Mr. Blue, who has $120,200 in assets and $40,200 in debt, and Ms. Green, who has $80,200 in assets and just $200 in debt—who do you think is better off? Of participants in the study, 79% said Ms. Green, although net worth is the same for both. When assessing those with positive net worth, having a lower degree of both assets and debt was seen as better than having more of each.

On the other hand, when considering a pair of individuals with equal negative net worth—say, Mr. Red, with $42,400 in assets and $82,400 in debt, and Ms. Gray, with just $400 in assets and $42,000 in debt—77% of respondents more often said that Mr. Red was wealthier. Having more assets, as well as more debt, was generally perceived as better.

What’s going on? Why do the trends move in opposite directions depending on whether the individuals were in the black or red? Sussman explains:

People generally like assets and dislike debt, but they tend to focus more on one or the other depending on their net worth. We find that if you have positive net worth, your attention is more likely to be drawn to debt, which stands out against the positive background. On the other hand, when things are bad, people find comfort in their assets, which get more attention.

These findings are more than just interesting—they seem likely to affect real lending and borrowing patterns. A second part of the study asked participants to imagine themselves in each of the scenarios, and then say how willing they would be to borrow money for purchases like a bathroom renovation or television. Again, people with positive net worth saw themselves as wealthier—and more willing to take on a loan—if they had fewer assets and debt to start with, and the reverse held true for those with negative net worth.

The study’s conclusions challenge traditional assumptions of classical economics—and, Sussman says, can be crucial in understanding otherwise puzzling economical choices we see in the real world.

The first Death Star from Star Wars (via Wookieepedia)

Obi-Wan: That’s no moon. It’s a space station.

That space station was the Empire’s first Death Star in Star Wars: A New Hope. Obi-Wan and company had just bounced through a debris field, the remnants of the planet Alderaan. Such an act of destruction would seem impossible to us–it seemed so to many of the movie’s characters until it happened. But perhaps not, say three students at the University of Leicester in England who last year published a study on the subject in their university’s undergraduate physics and astronomy journal.

The study’s authors start off by making some simple assumptions: The planet being fired upon doesn’t have some sort of protection, like a shield generator. And it’s about the size of Earth but solid through and through (Earth isn’t solid, but the planet’s layers would have significantly complicated the math here). They then calculate the planet’s gravitational binding energy, which is the amount of energy required to pull apart an object. Using the mass and radius of the planet, they calculate that destruction of the object would require 2.25 x 10³² joules. (One joule is equal to the amount of energy required to lift an apple one meter. 10³² joules is a lot of apples.)

The energy output of the Death Star isn’t given directly in the movie, but the space station was said to have had a “hypermatter” reactor that had the energy output of several main-sequence stars. For an example of a main-sequence star, the authors look to the Sun, which puts out 3 x 10²⁶ joules per second, and they conclude that the Death Star could “easily afford to output [the energy required for an Earth-like planet's destruction] due to to its tremendous power source.”

It would be a different story, though, if the planet scheduled for destruction had been more like Jupiter than Earth. The gravitational binding energy of Jupiter is 1,000 times that of the Earth-like planet in the study. “To destroy a planet like Jupiter [the space station] would probably have to divert all remaining power from all essential systems and life support, which is not necessarily possible.”

Of course, that assumes that the Emperor wouldn’t be willing to sacrifice a space station full of people to wipe out his enemies. And considering that he was just fine with wiping out whole planets, I’m not sure I’d take that bet.