Physicists Spot Einstein's Gravitational Waves for the First Time

SXS Collaboration, University of Chicago
SXS Collaboration, University of Chicago

Simulation of two merging black holes in front of the Milky Way. Scientists said the Sept. 14 event was so intense that in the moment before the colliding black holes swallowed each other, they emitted more energy than the rest of the universe combined.

After a decades-long search, physicists have managed to detect ethereal ripples in the very fabric of space, known as gravitational waves—triggered in this case by the death-spiral of a pair of merging black holes—and snared by a sophisticated detector known as LIGO, the Laser Interferometer Gravitational-wave Observatory. The discovery is being described as one of the great physics breakthroughs of the decade, on par with the 2012 discovery of the Higgs boson, and very likely Nobel Prize–worthy.

Lawrence Krauss, a physicist at Arizona State University and author of The Physics of Star Trek, told mental_floss that the discovery “monumental.” The new technology will allow astronomers “to peer into parts of the universe that we’d never could have seen otherwise,” Krauss said. More than that, it will pave the way for a new era in astronomy, one in which gravitational waves will be used to study a wide array of all astrophysical phenomena, many of them never before open to scientific scrutiny. “It’s opened up a whole new window on the universe,” he said—a metaphor that’s been echoed by many of the physicists and astronomers who have been weighing in excitedly on the discovery.

The discovery was unveiled Thursday morning at a packed Washington DC press conference organized by the U.S. National Science Foundation (NSF), which funded the research (with simultaneous presentations by partner institutions in at least four other countries).

The gravitational waves recorded by the LIGO detectors were the result of the violent merger of two black holes, located some 1.3 billion light-years from Earth, explained Gabriela González, a physicist at Louisiana State University and a spokesperson for the LIGO collaboration. One of the black holes was determined to have a mass 29 times that of our Sun, the other was even heavier, with a mass equal to 36 Suns. Although LIGO can only roughly pin down the direction of the signal, González said the black hole pair—now a single black hole, following the cataclysmic merger—is located in the southern sky, roughly in the direction of the Magellanic Clouds, the Milky Way’s small companion galaxies (of course, the black holes are far more distant).

The black hole pair had been locked in mutual orbit for hundreds of millions of years, gradually losing energy through the emission of gravitational waves, and then finally emitting one last “death burst” as the two objects merged into a single entity, González said. “What we saw is from only the last fraction of a second before the merger,” she told mental_floss.

The waves created from that final blast then rippled across the cosmos. After more than a billion years, some of those waves washed silently past Earth on September 14 of last year, where they triggered a tiny “blip” at each of the two identical LIGO detectors (one located in Hanford, Washington, the other in Livingston, Louisiana).

Incredibly, the team of researchers managed to keep the discovery relatively secret for almost six months. When the initial signal was recorded, Caltech physicist Kip Thorne received an e-mail from a colleague. “He said, ‘LIGO may have detected gravitational waves; go and look at this,’” referring Thorne to initial data posted on a private LIGO webpage. “I looked at it, and I said, ‘My god—this may be it!’” Thorne told mental_floss. (Thorne played a key role in the early development of LIGO and is known not only for writing some of the most-read books on gravitational physics, but for his collaboration with Carl Sagan on the book Contact, and with the makers of the smash sci-fi film Interstellar.)

Not everyone was quite so tight-lipped—and in fact rumors had been circulating for weeks leading up to Thursday’s announcement (as mental_floss reported last month). A few people got an early look at the results and couldn’t contain their excitement. McMaster University physicist Clifford Burgess emailed some of the details to colleagues in his department, and the news quickly spilled out via social media. (Burgess described the discovery as “off-the-scale huge.”)

And while there have been a somewhat alarming number of super-hyped physics “discoveries” that failed to pan out in recent years—remember the faster-than-light neutrinos?—the LIGO researchers claim to have ruled out any possible non-gravitational-wave explanation for the signal they recorded. The finding is being published in the peer-reviewed journal Physics Review Letters (the “discovery paper” was released yesterday morning, February 11), along with a series of further papers.

It’s a discovery nearly a quarter-century in the making: LIGO was spearheaded by Caltech and MIT in 1992, and now involves nearly 1000 researchers from the UK, Germany, Australia, and beyond. With a total cost of more than $600 million, LIGO is the largest project ever funded by NSF.

Einstein predicted the existence of gravitational waves, based on his newly developed theory of gravity, known as general relativity, in 1915. Gravitational waves are literally ripples in spacetime, created whenever massive objects throw their weight around—for example, when ultra-dense stars, known as neutron stars, collide, or when a star blows up in a supernova. In fact, any time masses accelerate, gravitational waves are produced—even doing dumbbell-lifts at the gym would produce them—but such waves would be infinitesimally weak, and quite impossible to measure. Even the waves from the black hole merger were so faint that they required the massive LIGO detectors to finally pick them up.

“It’s just really, tremendously exciting,” physicist Clifford Will of the University of Florida, one of the world’s leading authorities on general relativity, told mental_floss. “We’ve just finished celebrating the 100th anniversary of GR [general relativity], so this is icing on the cake.”

David Spergel, a physicist at Princeton, tweeted: “Up to now, we have only seen the universe. Now, for the first time, we can hear," adding, "The universe is playing a beautiful tune and LIGO just heard it.”

Gravitational waves alternately stretch and shrink space, by a tiny amount, as they pass by. Inside each of the LIGO detectors, laser beams bounce back and forth between mirrors attached to weights. A passing gravitational wave causes a slight change in the distance the laser beam travels, which leaves a telltale pattern (known as an interference pattern) in the recorded laser light. (Having two detectors located more than 2000 miles apart helps rule out false-alarm signals that might register at only one site.)

“We saw the same waveform—the same signal—in the two detectors,” González told mental_floss. Recording such signals by chance might happen “once in every 200,000 years,” she said.

LIGO went online in 2002, but with only a fraction of its current sensitivity. The detectors were upgraded last fall in an effort known as “Advanced LIGO.” The actual stretching caused by the passing gravitational wave is mind-bogglingly small, causing the detectors to grow or shrink in length by a distance equivalent to just 1/1000th of the width of a proton.

The success of the LIGO detectors is “a wonderful testament to the perseverance and ingenuity of the scientists,” Krauss said. “I never thought I’d see this in my lifetime.”

Astronomers and physicists expect the new technique to reveal the universe in a new light, as the first optical telescopes did when Galileo first used them to study the night sky 400 years ago, and as the first radio telescopes did in the mid-20th century.

Editor's note: This story has been significantly updated to include input from a main LIGO researcher and additional outside experts, as well as with more comprehensive details about the extraordinary find.

New Cross-Bred Cosmic Crisp Apples Can Stay Fresh for Up to a Year

Cosmic Crisp
Cosmic Crisp

Healthy snackers know only too well the disappointment that comes with biting into what looks like a deliciously crisp apple and getting a mouthful of mealy mush instead. It’s just one of the pome fruit’s many potential issues—they also brown quickly, bruise easily, and don’t last as long as whatever bag of chips you might be tempted to reach for instead.

Enter the Cosmic Crisp, a Washington-grown patented hybrid apple that could be the answer to all your apple-related complaints. According to New Atlas, researchers at Washington State University began breeding the new variety as a cross between Enterprise and Honeycrisp apples in 1997, and it’s officially hitting stores now.

cosmic crisp apple on tree
Cosmic Crisp

Not only does a Cosmic Crisp apple resist bruising and browning better than other kinds of apples, it also boasts an exceptionally long storage life. In a controlled atmosphere, it should stay fresh for a full year—meaning you’ll soon be able to enjoy a crisp, satisfying snack in the middle of March, when out-of-season apples usually leave much to be desired. In your own refrigerator, Cosmic Crisp apples are good for about six months, and they’ll even last for several weeks if you leave them out at room temperature. The long shelf life might cut down on the number of apples that you end up tossing in the trash because they went bad before you got around to eating them.

In a 2012 report published in the American Society for Horticultural Science journal HortScience, the Washington State University researchers found that a group of 114 consumers rated the Cosmic Crisp apple, or WA 38, higher than Fuji apples in sweetness, sourness, flavor intensity, crispness, firmness, juiciness, and overall acceptance. The apple's website even suggests that bakers can reduce the amount of added sugar in recipes that contain Cosmic Crisps.

The Cosmic part of its name comes from the whitish specks on the apple’s skin, which reminded taste testers of a starry sky. In reality, those specks are lenticels—porous openings that allow the apple to exchange gases with its environment.

If you don’t see Cosmic Crisp apples in your grocery store yet, here’s a simple trick for keeping any apples fresh for longer.

[h/t New Atlas]

The Reason So Many Babies Are Conceived in Winter

yurizhuravov/iStock via Getty Images
yurizhuravov/iStock via Getty Images

Does it feel like many friends and family members announce the pending arrival of a baby during the fall and winter months? That’s not exactly a coincidence. It turns out the cold season is associated with more reproductive activity than any other time of the year. The month of December alone accounts for 9 percent of conceptions in the United States. Science is gaining a better understanding of why.

All living creatures heed an evolutionary instinct to target seasonal births. If conception happens during colder months, babies will be born during warmer months, when resources will be bountiful. Northern states have births peaking in June and July, while southern states come a bit later in October and November. The farther south, the later the birth peak, since people in these warm climates are less influenced by frigid temperatures.

What are frisky humans responding to in colder months? Research suggests that the cooler temperatures and shortened days signal that it's time to get busy. Other theories suggest that men may be more fertile in colder months, or that a woman’s ovum receptivity might change with decreased daylight. Not only are couples potentially more sexually active, but that activity might wind up being more (re)productive.

Are there benefits to conceiving at other times? Possibly. One 2013 study published in the Proceedings of the National Academy of Sciences gathered data from nearly 1.5 million births and found that average birth weight in the first five months of the year decreased by 10 grams. Babies born during the summer months were 20 grams heavier. Mothers who conceived in summer tended to gain more weight than those who conceived at other times.

If you have a disproportionate amount of friends with a September birthday, it’s likely that their parents consciously or unconsciously followed their evolutionary instinct nine months earlier.

[h/t Smithsonian]

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