James' World 2

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In 1974, Stephen Hawking theorized that the universe’s darkest gravitational behemoths, black holes, were not the pitch-black star swallowers astronomers imagined, but they spontaneously emitted light — a phenomenon now dubbed Hawking radiation. 

The problem is, no astronomer has ever observed Hawking’s mysterious radiation, and because it is predicted to be very dim, they may never will. This is why scientists today are creating their own black holes.

Researchers at the Technion-Israel Institute of Technology did just that. They created a black hole analog out of a few thousand atoms. They were trying to confirm two of Hawking’s most important predictions, that Hawking radiation arises from nothing and that it does not change in intensity over time, meaning it’s stationary.

“A black hole is supposed to radiate like a black body, which is essentially a warm object that emits a constant infrared radiation,” study co-author Jeff Steinhauer, an associate professor of physics at Technion-Israel Institute of Technology, told Phys.org. “Hawking suggested that black holes are just like regular stars, which radiate a certain type of radiation all the time, constantly. That’s what we wanted to confirm in our study, and we did.”

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Image credit: Aaron Horowitz via Getty Images)

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On September 16, 2011, an anime fan posted a math question to the online bulletin board 4chan about the cult classic television series The Melancholy of Haruhi Suzumiya. Season one of the show, which involves time travel, had originally aired in nonchronological order, and a re-broadcast and a DVD version had each further rearranged the episodes. Fans were arguing online about the best order to watch the episodes, and the 4chan poster wondered: If viewers wanted to see the series in every possible order, what is the shortest list of episodes they’d have to watch?

In less than an hour, an anonymous person offered an answer — not a complete solution, but a lower bound on the number of episodes required. The argument, which covered series with any number of episodes, showed that for the 14-episode first season of Haruhi, viewers would have to watch at least 93,884,313,611 episodes to see all possible orderings. “Please look over [the proof] for any loopholes I might have missed,” the anonymous poster wrote.

The proof slipped under the radar of the mathematics community for seven years — apparently, only one professional mathematician spotted it at the time, and he didn’t check it carefully. But in a plot twist in late-2018, the Australian science fiction novelist Greg Egan proved a new upper bound on the number of episodes required. Egan’s discovery renewed interest in the problem and drew attention to the lower bound posted anonymously in 2011. Both proofs are now being hailed as significant advances on a puzzle mathematicians have been studying for at least 25 years.

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Raul Puente-Martinez has been pierced by quite a number of cactuses in his time. A research botanist and curator of living collections at the Desert Botanical Garden in Phoenix, he’s been studying prickly pears and chollas, which are infamous for their barbed spines, for decades. However, the worst cholla attack he’s ever witnessed came while he was hiking with several friends in Mexico. As they strolled through a cholla forest, one of the hikers discovered a chunk of cactus stuck to the tip of his shoe. He tried kicking his foot out to dislodge the spiny hitchhiker. Sure enough, most of the cactus flew off—including one piece that shot straight up and became stuck in the man’s upper lip.

Luckily, Puente-Martinez has had a lot of practice with removing spines. “You could see that they were really deep inside his lip,” he recalls. “Every time I pulled one, there was this little stream of blood coming out of the hole; that was pretty bad.”

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