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

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.

This Just In
Yes, Parents Do Play Favorites—And Often Love Their Youngest Kid Best

If you have brothers or sisters, there was probably a point in your youth when you spent significant time bickering over—or at least privately obsessing over—whom Mom and Dad loved best. Was it the oldest sibling? The baby of the family? The seemingly forgotten middle kid?

As much as we'd like to believe that parents love all of their children equally, some parents do, apparently, love their youngest best, according to The Independent. A recent survey from the parenting website Mumsnet and its sister site, the grandparent-focused Gransnet, found that favoritism affects both parents and grandparents.

Out of 1185 parents and 1111 grandparents, 23 percent of parents and 42 percent of grandparents admitted to have a favorite out of their children or grandchildren. For parents, that tended to be the youngest—56 percent of those parents with a favorite said they preferred the baby of the family. Almost 40 percent of the grandparents with a favorite, meanwhile, preferred the oldest. Despite these numbers, half of the respondents thought having a favorite among their children and grandchildren is "awful," and the majority think it's damaging for that child's siblings.

Now, this isn't to say that youngest children experience blatant favoritism across all families. This wasn't a scientific study, and with only a few thousand users, the number of people with favorites is actually not as high as it might seem—23 percent is only around 272 parents, for instance. But other studies with a bit more scientific rigor have indicated that parents do usually have favorites among their children. In one study, 70 percent of fathers and 74 percent of mothers admitted to showing favoritism in their parenting. "Parents need to know that favoritism is normal," psychologist Ellen Weber Libby, who specializes in family dynamics, told The Wall Street Journal in 2017.

But youngest kids don't always feel the most loved. A 2005 study found that oldest children tended to feel like the preferred ones, and youngest children felt like their parents were biased toward their older siblings. Another study released in 2017 found that when youngest kids did feel like there was preferential treatment in their family, their relationships with their parents were more greatly affected than their older siblings, either for better (if they sensed they were the favorite) or for worse (if they sensed their siblings were). Feeling like the favorite or the lesser sibling didn't tend to affect older siblings' relationships with their parents.

However, the author of that study, Brigham Young University professor Alex Jensen, noted in a press release at the time that whether or not favoritism affects children tends to depend on how that favoritism is shown. "When parents are more loving and they're more supportive and consistent with all of the kids, the favoritism tends to not matter as much," he said, advising that “you need to treat them fairly, but not equally.” Sadly for those who don't feel like the golden child, a different study in 2016 suggests that there's not much you can do about it—mothers, at least, rarely change which child they favor most, even over the course of a lifetime.

[h/t The Independent]

15 Scientific Reasons Spring Is the Most Delightful Season

Summer, winter, and fall may have their fans, but spring is clearly the most lovable of the four seasons. Not convinced? Here are 15 scientific reasons why spring is great:


road and field on a sunny day

Spring marks the end of blistering winter and the transitional period to scorching summer. In many places, the season brings mild temperatures in the 60s and 70s. People tend to be most comfortable at temperatures of about 72°F, research shows, so the arrival of spring means you can finally ditch the heavy winter layers and still be comfortable.


sunny sky

Following the spring equinox, days begin lasting longer and nights get shorter. Daylight Saving Time, which moves the clock forward starting in March, gives you even more light hours to get things done. Those extra hours of sun can be a major mood-booster, according to some research. A 2016 study of students in counseling at Brigham Young University found that the longer the sun was up during the day, the less mental distress people experienced.


blue bird on branch

Many animals migrate south during the winter, then head north as temperatures rise. For relatively northern regions, there is no better indicator of spring than birds chirping outside your window. Their northward migration can start as early as mid-February and last into June, meaning that throughout the spring, you can expect to see a major avian influx. In addition to the satisfaction of marking species off your bird-watching checklist, seeing more of our feathered friends can make you happy. In 2017, a UK study found that the more birds people could see in their neighborhoods, the better their mental health.


Baby squirrels

Many animals reproduce in the spring, when temperatures are warmer and food is plentiful. Baby bunnies, ducklings, chipmunks, and other adorable animals abound come spring. Studies have found that seeing cute animals can have positive effects on humans. For instance, one small study in 2012 found that when college students looked at cute images of baby animals, they were better at focusing on a task in the lab. Being able to watch fluffy baby squirrels frolic outside your office window might make spring your most productive season of the year.


flowers hanging outside of a house

In 2015, a pair of public policy researchers discovered a hidden upside to "springing forward" for Daylight Saving Time. It reduced crime. When the sun set later in the evening, the study published in the Review of Economics and Statistics found, robbery rates fell. After Daylight Saving Time started in the spring, there was a 27 percent drop in robberies during that extra hour of evening sunlight, and a 7 percent drop over the course of the whole day.


child with rainbow umbrella jumping in puddle

Warmer temperatures mean you can spend more time outside without freezing your feet off, which is great for mental health. Across the seasons, research has found that taking walks in nature slows your heart rate and makes you more relaxed, but some research indicates that there is something special about spring's effect on your brain. A 2005 study from the University of Michigan linked spending 30 minutes or more outside in warm, sunny spring weather to higher mood and better memory. But the effect reverses when spring ends, since being outside in the warmest days of summer is usually pretty uncomfortable.


woman writing in a park

That same University of Michigan study found that spending time outside in the sunny spring weather isn't just a mood booster, it actually can change the way people think. The researchers found that being outdoors broadened participants' minds, leaving them more open to new information and creative thoughts.


leaves budding in spring

Spring brings green growth back to plants and trees. Depending on where you live, trees may begin sporting new leaves as early as mid-March. That successful spring leaf growth ensures a cool canopy to relax under during the hot summer—a hugely important factor in keeping cities comfortable. According to researchers, vegetation plays a big role in mitigating the urban heat island effect. When trees release water back into the air through evapotranspiration, it can cool down the areas around them by up to 9°F, according to the EPA.


tulip bulbs

It's amazing what a little sun can do for plants and grass. Through photosynthesis, plants convert sunlight, carbon dioxide, and water into food, releasing oxygen in the process. That means as plants start to grow in the spring, they pull carbon out of the atmosphere, providing an important environmental service. Plants take in roughly 25 percent of the carbon emissions humans produce, absorbing more than 100 gigatons of carbon through photosynthesis each growing season. Because of this, the amount of carbon dioxide in the atmosphere drops each spring and summer. (Unfortunately, it rises in the winter, when most plants aren't growing.)


wooden box full of fresh produce

Many vegetables and some fruits are harvested in the spring. 'Tis the season to get your local asparagus, greens, peas, rhubarb, and other fresh produce. Getting more fruits and vegetables into your diet isn't just good for the body; it's good for the soul. A 2016 study of more than 12,000 Australians found that when people increased the amount of fruits and vegetables in their diet, they felt happier and had higher rates of life satisfaction. If they increased their intake by eight portions a day (a tall order, we know) the psychological gains were equivalent to the change in well-being people experience when they go from being unemployed to having a job, the researchers found.


Flowers in a vase

After months spent conserving energy, flowers bloom in the spring, once they sense that the days have grown longer and the weather has turned warmer. That's good for humans, because several studies have shown that looking at flowers can make you happy. A 2008 study of hospital patients found that having flowers in the room made people feel more positive and reduced their pain and anxiety [PDF]. Another study from Rutgers University found that when participants were presented with a bouquet of flowers, it resulted in what scientists call a "true smile" a full 100 percent of the time. Seeing flowers had both "immediate and long-term effects" that resulted in elevated moods for days afterward, according to the researchers [PDF].


woman tying shoes in flower field

While it's important to keep moving no matter what the weather, research shows that working out can be more beneficial if you do it outside. A 2011 study found that, compared with an indoor workout, exercising outdoors in nature increased energy levels, made people feel revitalized, and decreased tension, among other positive effects. People who worked out in the fresh air also tended to say they enjoyed the experience more and would be likely to repeat it, suggesting that using nature as your gym might help you stick with your exercise regimen. While those benefits probably extend to winter, too, it's a whole lot easier to stomach the idea of a run once the weather warms up.


dew on grass and a daisy

Flu season in the U.S. typically lasts through the fall and winter, usually peaking between December and February and tapering off during the spring. The seasonal change is in part because of dry air. Cold temperatures mean a drop in humidity, and indoor heating only makes the air drier. This lack of moisture in the air can dry out your skin and the nasal cavities, leading to nose bleeds, irritated sinuses, and a greater risk of getting sick. Since the mucus in your nose is designed to trap viruses, when it dries up, you're more likely to catch something nasty, like the flu. As the weather warms up and becomes more humid throughout the spring, that mucus comes back. As the season wears on, not only can you lay off the body lotion, but you can probably put away the tissues—if you don't have spring allergies, that is.


windows open on a red house

Temperate weather makes it easier to get the fresh air you need. Opening your windows and allowing the breeze in serves as an important way to ventilate indoor spaces, according to the EPA. A lack of ventilation can lead to an unhealthy concentration of indoor pollutants from sources like cleaning product fumes, certain furniture and building materials, and stoves (especially gas ones), posing a threat to your health and comfort. Winter brings the highest rates of indoor pollutants like nitrogen oxide, a 2016 study of unventilated stove use in homes found. Spring brings the perfect opportunity to throw open those windows and doors and get the air moving again.


woman enjoying sitting in the sun

Sunlight triggers your body to produce the vitamin D, which keeps your bones strong. At northern latitudes, it's extremely difficult to get enough sun exposure naturally to maintain healthy vitamin D levels during the winter—even if you did want to expose your skin to the elements—but that starts to change during the spring. One Spanish study found that in Valencia (which shares a latitude with Philadelphia, Denver, Baltimore, Kansas City, and several other major U.S. cities), people only need 10 minutes outside with a quarter of their bodies exposed to the spring sunshine to get an adequate daily dose of vitamin D.

A version of this story originally ran in 2014.


More from mental floss studios