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musicollage · 4 years ago

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Plaid — The Digging Remedy. 2016 ; Warp. ~ [ Album Review | 1) Pitchfork + 2) Headphone Commute + 3) Resident Advisor + 4) Pop Matters + 5) Exclaim! + 6) Igloo Magazine + 7) Treble + 8) Soundblab ]

1) As hard as it is to believe that Warp Records mainstays Plaid have been making experimental electronic music now for over twenty-five years, it’s even harder to believe that they’ve managed to do without markedly adjusting their basic formula for success. Plaid have staked out a well-defined musical territory for themselves by choosing on each new record to continually mine their existing plot of land rather than explore new terrain elsewhere. Their latest album, the appropriately named The Digging Remedy, reiterates that the Plaid game plan remains intact.

Luckily for Plaid, their game plan has usually been a pretty good one. Their music is a unique strain of listenable, hyper-melodic experimental electronic music that fits the frequently maligned tag “Intelligent Dance Music” all while sounding truly like no one else. They’ve also never made a truly bad album, which isn’t easy to say for a band who’ve been together that long, both in their current incarnation as Plaid and in the past life as the Black Dog with Ken Downie (anywhere from 10 to 15 records depending on how you’re counting). If nothing else, the Plaid blueprint is strong, unique and reliable.

The Plaid coming to us now on The Digging Remedy is in a sort of fourth stage: from the early Black Dog years running from ‘91-‘95; to the first Warp trifecta golden era of ‘95-02; to the experiments and soundtracks of ‘03-'12; and finally in 2014, they hit a wizened, back-to-basics phase. 2014’s Reachy Prints returned to the warm tones and friendly melodies that had worked so well for them over the previous twenty years. Now, two years later, The Digging Remedy picks up where its predecessor left off.

One tradition that The Digging Remedy also carries on is the somewhat odd placement of an album opener that is distinct (and often superior) from anything else on its accompanying record. 2001’s Double Figure opener “Eyen,” with it’s fade-in intro, circular acoustic guitar arpeggio and coo-ing choral vocals sounded beautiful and stands out from the rest of the album. The first two minutes of “Even Spring” from 2003’s Spokes, featuring Leila-collaborator Luca Santucci’s ghostly vocals, sounded even further away (before returning to “standard Plaid” mid-song). And Scintilli’s delightfully exquisite “missing” is perhaps the most unique track in their catalog, incorporating vocals not for lyricism but as a new instrument. On The Digging Remedy, lead track “Do Matter” lays down a tone of ominous, reflective menace that feels like a perfect development for the band: after years of playfulness and warmth, the idea of imagining a darkwave Plaid record that turns that warmth into nightmare feels like a potential home run.

Alas, that dream is not to be, as second track “Dilatone” drags the mood back to familiar territory. The jarring transition from “Do Matter” to “Dilatone,” a slight track that spins in tiny circles while going nowhere, represents one of The Digging Remedy’s biggest weak spots. Though the album reaches greater heights than its predecessor Reachy Prints with a number of excellent compositions (“Do Matter,” “Clock,” “Melifer,” “Yu Mountain,” “Saladore”), the sequencing of everything just feels a bit off, in a way that seems uncharacteristic. Too often, the momentum of a great track is followed by the slow thud of something both different and lesser. The deliberate build and pitter-patter Knight Rider paranoia of “Saladore”—the closest thing to “Do Matter”’s ghoulishness—is wonderful, but to have it wind down into the bass drum circus thump of “Reeling Birds” feels like bit of a let down.

The good news about The Digging Remedy is that it’s lovely and listenable for any longtime followers, or for anyone remotely interested in the kind of melodic IDM defined by this piece. However, it is neither an exciting deviation nor a refinement; as such, it’s really just more of an already-good thing, albeit packaged less delicately. Few artists can say that twenty-five years in they are still able to put out quality records. But here’s to hoping that next time around Plaid might consider stepping off their lawn to chase that darkwave dream.

2) I’ve been observing some of my friends’ listening habits and their music consumption trends. Some just seemingly follow paths in no particular direction; some use music to counteract their moods (when tired, looking for the up-beat rhythms); others, like me, find sounds to compliment their state of my mind (even during angry moments, angry music sounds great). By now, I’ve got a music collection spanning years of continuous play, so what in the world would I play? This morning, I am in a particular “cerebral” mood, caffeine streaming through my blood, the sun already shining on upcoming hours of the unknown, and I need that something to stimulate my mind. And, without even thinking twice about it, I turn to the latest release from Plaid. Again…

Those following the output of Ed Handley and Andy Turner since the early 90s, need no introduction to the group. And, chances are, that if you’re reading this, you’ve been converted to a fan. So what’s a writer to do, when covering The Digging Remedy, but regurgitate the history that led us to this very moment? For that, I’ll leave it to the rest, or past reviews of Reachy Prints (Warp, 2014) or Tekkonkinkreet (Aniplex, 2006), and turn directly to the sounds explored on this latest full-length studio album, released, of course, on their home label, Warp. At nearly 45 minutes in length, I also like to pair the album with On Other Hands, a 19-minute EP with four more tracks to round-up and compliment the tale.

Plaid’s story-telling is impeccable. Each piece is a microcosm of unfolding narrative, gliding around the harmonic scale with maximum precision and minimum exertion. While most electronic musicians tend to focus on advance technology trends (and this I say without much negative connotation), Plaid’s sound excels on what Turner and Handley have always done best – deliver exquisite quality in each and every track. The sounds on The Digging Remedy seem to freely breathe in an architectural foundation of rhythmic structure, definitive space layouts, and deliberate sequencing. The album delivers a particularly pleasurable sonic experience while consumed through an audiophile-grade gear (FLAC + Grace Design m903 + Audeze LCD-X on this side of the pond).

The melodic progressions keep my mind occupied with every twist, echoing my earlier desire to stimulate the thought. While the cover of the album features an “edgy” geometrical kaleidoscope of figures, the music offers a smoother ride into a universe of gorgeous harmony and immediately memorable melodies (“Saladore”, for example, is a perfect marriage between an up-beat glitchy rhythm and a beautiful theme that you’d wish would go on for another twenty minutes). Keeping the “intelligent” part of IDM, Plaid continues to explore their distinct contribution to the evolution of music, long after the rest have put their arms to rest. A perfect way to set your brain awake and unfold the intricate puzzles that reward with further listens. For more pleasant surprises visit thediggingremedy.com. Highly recommended!

3) It's startling to realize that Ed Handley and Andy Turner have been making electronic music consistently for 27 years—first as members of The Black Dog and then, since '91, as Plaid. And all of that experience adds up to a distinct fluidity in their music. Smooth transitions and bright melodies have always been hallmarks of Plaid's music, and The Digging Remedy is no exception—essentially, this is the same accomplished electronica we've come to expect from the two Englishmen.

Handley and Turner have been mining the same futuristic aesthetic for more than 20 years—after that long it starts to feel quaint. To their credit, they refresh it enough to feel contemporary. Sleek polish and careful sound design help the music stand up against their peers from the younger generation, such as producers like Konx-Om-Pax or Boxcutter.

But The Digging Remedy's tried-and-true approach can feel somewhat lacking. What starts with a John Carpenter-esque direction on opener "Do Matter" blossoms briefly with the multirhythms of "Dilatone" and into a sparkling patina of melodic elements on "CLOCK." But by the fourth track, the album slips away into background listening. This is partly due to how many tracks have similar pacing and energy, creating an intentional smoothness that winds up cloying. As a whole, the music is warm and pleasant, even occasionally gorgeous, but it feels a bit bloodless. The effect is compounded by the addition of somewhat smug-sounding (and dare I say it, middle-aged) worldbeat flute and guitar from multi-instrumentalist Benet Walsh, especially on closing tracks "Held" and "Wen."

Perhaps the biggest problem, then, is the absolute ease in which Handley and Turner handle themselves. If any part of the production process—whether in practice or emotion—felt tricky or rough, you wouldn't be able to tell. The moments of small disruption that draw you out of The Digging Remedy's electronica stupor—like the staccato intro to "CLOCK" or the way "Saladore" edges towards the dance floor—are reminders of why Plaid are important. But it's not enough to dislodge a sense of complacency that feels out of step with their reputation as innovators.

4) In the milieu of '90s British IDM, Plaid was sort of a peculiar example. They do not have the LSD soaked psychedelic weirdness or nosiness of Aphex Twin, nor the jazzy drum and bass underpinnings of Squarepusher, nor the stark abstraction of Autechre. What they do have is a preternatural sense of melody and capacity for writing memorable songs. At times, Plaid’s music almost feels more akin to post-rock bands from the U.S. like Tortoise or Pele than their Warp label mates of the '90s. There is lovely warmth that runs through their music that is almost the inversion of Autechre’s unsettling coldness. Although Plaid do on occasion sample traditional instruments, it is never clear exactly when they are doing so. The listener can easily imagine a live band reinterpreting these songs on traditional instruments, something that is hard to imagine with most of their electronic peers. The Plaid sound is well established and they do not seem very interested in reinventing the wheel, and why should they be?

On their new record The Digging Remedy Plaid provide us with one of the most satisfying examples of the Plaid sound yet recorded. Although Plaid have never dropped the ball or wandered off into ill-advised self-indulgence, they have not sounded this strong or consistent since 1999’s stunning classic Rest Proof Clockwork. These songs are catchy. The kind of catchy that makes ass wiggling and repetitive head bobbing down-right mandatory. Listeners should prepare themselves for goofy Charlie Brown-esc grins that might make you look a little bit demented on public transportation or at the gym, so be careful where you choose to listen to The Digging Remedy.

On tracks like "Melifer", Plaid have all of their strongest traits on display: hooks that will not leave your brain for days, beats that grove and bump like the finest hip-hop, and a sense of timing and songcraft that knows just what to do and when. "Melifer" is fairly short, barely four minutes long, so don’t be surprised if you feel the need to listen to this one over and over. The Digging Remedy’s 12 tracks zip by without any filler to be found, downright begging repeated listens.

It has always seemed to me that Plaid must have an abiding love for dub music and possibly other Caribbean genres like calypso. The fingerprints of dub can be felt throughout The Digging Remedy, and I do notmean dubstep, I mean Lee ‘Scratch’ Perry-ish abstractions that sound like they were beamed down from space. The tinkling and pleasant bonking audible on many of Plaid’s records, including the The Digging Remedy, often remind the listener or steel drums. All of this contributes to the signature Plaid sound, which is always warm, joyful, and spacious.

Those of you hoping for a curve ball of some kind from Plaid might be disappointed with the The Digging Remedy. This record sounds exactly like what it is: a Plaid record. Most listeners, however, will be delighted by every moment of The Digging Remedy. It is a summertime record if ever there was one, filled with sunshine and nostalgia. It just goes to show that there will always be room in the world for more hook infested, balmy electronic music that makes you grin like an idiot.

5) When you've been around since 1991, you basically have two options: get with the times, or latch more firmly onto the sound that was your making. Like the Prodigy or the Chemical Brothers, Plaid have opted for the latter option, but unlike those two, they can still pull it off.

Thankfully, they got out of their fruitless movie soundtrack cul-de-sac a few years ago, returning to Warp with Scintilli in 2011. Since then, they've rolled out a nice collection of quirky blips that fit snugly into the sound they've established, if perhaps a little too snugly.

The Digging Remedy follows the same format as a large chunk of Plaid's albums, in that it's got some amazing tracks — good enough to justify the legendary status that they've achieved — but enough average ones that the finished product inevitably gets pulled back to a few shades above mediocrity. Leading the pack are tracks like the hair-raising opener "Do Matter," "Yu Mountain," with its beautiful cacophony of clangs, and "CLOCK," which uses that ever-satisfying, old IDM chestnut of a bouncing ball effect to much success. Such heights are then marred, however, by some atonal, flute-like elements on "Lambswood."

One thing that Plaid have gotten consistently better at, however, is subtlety. There's nary a track on The Digging Remedy that doesn't gradually introduce elements into view, like landmarks slowly appearing on the horizon, a tack they've nailed since their return to Warp. It's only gotten better since their last album, Reachy Prints.

Plaid remain enjoyable, if a little stuck in a rut. Staunch Plaid fans will find plenty of joy in The Digging Remedy, but then, why wouldn't they? They've heard this record before.

6) There’s never been a dull moment in the near twenty-five years spent exploring the plaid-wallpapered, carpeted, upholstered, veneered and lacquered dwellings architected by the inimitable Ed Handley and Andy Turner. Well, except, of course, for those few barren years when nothing new appeared on the landscape.

Back in the early noughties, Plaid began strolling nonchalantly down almost Autechrean side-alleys that led them away from the wildly eclectic collages of Not For Threes and the playful quirkiness of Rest Proof Clockwork, with Double Figure pointing towards a more abstract world that culminated in the blistering sound-design of the by turns stunning then alienating anomaly that was Spokes.

Three years later, a worrying foray into collaborative audiovisual work on Greedy Baby that largely failed to create imagery that lived up to the caliber of their compositions seemed to ominously prefigure that which every fan surely dreads: a move into film soundtracks. I mean, seriously, does anyone really love it when one of their favorite acts goes down this route? It marked the end of Plaid as a prolific major player in the electronic music scene for another five years as they went dark from the Warp roster.

How wonderful it was to have them back in 2011 with the exquisitely crafted Scintilli, refreshed, recharged and bursting at the seams with new ideas. So what is this digging remedy then? Have Ed & Andy been spending time in the back garden unearthing the seeds, relics and keepsakes that were the roots of past glories as a palette cleanser to that stark, sound-design oriented material? Reachy Prints hinted at this, and listening to The Digging Remedy it’s easy to imagine that to be the case.

Nobody could accuse Plaid’s work of being unsubtle, and it’s the lack of immediacy borne of that which makes Plaid’s music such a joy to revisit. There’s always something new to discover on a Plaid record, but it really has to be said that since the release of Reachy Prints they’ve taken this to new levels.

Both that album and The Digging Remedy are not just melodically subtle, but subtly complex, both in the production and arrangements. Witness, too, just how short their recent output is compared with the more experimental, noodling days of Not For Threes, wonderful though they were. Nothing on The Digging Remedy is over four and a half minutes long, yet there’s nary a single track that feels underdeveloped.

With the possible exception of the terminally infectious “Saladore” perhaps, but maybe that’s simply because it’s so good? At just under four minutes, Plaid spend two building and layering some of their most insistent, stuttering and rapid-fire percussion in years, adding tumbling keys, then airy melodic pads, before finally topping them with sublime strings in the final minute. And it has the indecency to end there, the swine!

On opening builder “Do Matter,” the crystalline shards and prismatic beams that made the most memorable moments of Spokes and Scintilli come alive are present but so is an overarching Tomorrow’s Harvest sense of foreboding that carries over into the nervy “Baby Step Giant Step.”

Pronounced nods to the past appear on “Dilatone,” which on the surface sounds like it could easily have appeared on Not For Threes alongside “Abla Eedio” or “Prague Radio”. The sublime “CLOCK” employs that old IDM favourite: the bouncing ball effect. Only instead of it being migraine-inducing, Plaid make this both fun and nostalgia-pinging. It culminates in a frenetic, colorful melange of everything we’ve come to know and love about Plaid.

The acoustic touches of Rest Proof Clockwork shine brightly here too, even though they don’t necessarily illuminate many of The Digging Remedy‘s finest moments. “The Bee” is “Dang Spot” silly but fails to ignite on account of sounding so out of place and the penultimate “Held” warbles cheerfully enough, but merely skates above a lake of pretty. The closing “Wen,” however, is every bit as graceful and delicately nuanced as tracks like “Ralome” or “Gel Lab” whilst adding to the mix all those tricks they’ve accumulated from their soundtrack work.

Even when returning to the polished chrome of Double Figure Plaid are surpassing themselves, as evinced by the melodic delicacy of the quieter moments of “Yu Mountain” interspersed with all the clatter and clang. Another highlight of that album was also one its most atypical moments, the sublime acoustic-guitar led “Eyen” twinkling wryly amongst its other glitzy, over-polished and hyperactive brethren. The spellbinding “Melifer” mines a similar vein with its gorgeously composed guitar melodies, at first ruminative then positively chipper as they whistle through trademark metallic instruments.

Ultimately, The Digging Remedy feels like a perfectly natural successor to Reachy Prints, with Plaid firmly back where they belong: luring us in with quirky, brightly colored and accessible melodies, then trapping us in their dizzying maze of surprise, delight and hidden depths. Keep digging.

7) It’s the age-old conundrum of the music fan: Do we want progress or consistency, or both from our favorite artists? Plaid’s latest album The Digging Remedy certainly has plenty of consistency, which would be troubling had it not followed 2014’s Reachy Prints, where steady veterans’ hands made as straightforward and entertaining a release as exists in the Plaid catalog. But it also tentatively steps (back, again) into curious and experimental territory; if Reachy Prints found the electronic duo in 4/4 attack mode, The Digging Remedy suggests subsequent synthesized decay.

Andy Turner and Ed Handley create a lot of music here that’s just slightly off-kilter and imperfect, and therefore often quite interesting. This is dance music run through Sonic Youth tunings (“Yu Mountain”), Autechre patches (“Dilatone”), and uneven time signatures (“Baby Step Giant Step”). The duo also offer neotraditional songwriting structures aping the discography of Massive Attack or some live EDM band. At its best, we get the sinewy “Melifer” and the guitar kerrang of “The Bee.” At its worst—which still isn’t bad, mind you—the album loses gathered momentum in its back quarter (from “Reeling Spiders” on), veering dangerously close to smooth jazz.

But the heart of Plaid and The Digging Remedy remains disarming leftfield takes on 1990s electronica tropes. “Lambswood” is straight-up Buddha Bar material while “CLOCK” cycles through various iterations of synth-stabbing ecstatic house, tiptoeing on the edge of chaos. “Saladore,” meanwhile, is a throwback to the heady innovation of early IDM, the hard-charging stormer of the album that recalls the birth of Warp—Plaid included. After a quarter-century of making music that embraces how things change, it’s somehow comforting to hear Turner and Handley staying the same.

8) Andy Turner and Ed Handley, working under the name Plaid, have been around the block once or twice, and they've established themselves with a very unique, recognizable sound wholly their own. Their newest set, The Digging Remedy, finds them staying comfortably nestled in the well worn path they've carved out for themselves over the years.

The first track, 'Do Matter', was surprising, in that it felt like a more generic, undefined sound than I'd expect from the duo. It wasn't bad, just a very basic ambient electronic track, a weightless little thing that could have been created by any of dozens of other artists. But things quickly fell back into place with the next song, 'Dilatone', and it was like putting on an old, comfortable shoe. That distinct, bleepy clickety percussion was front and center, and it was like I'd taken a trip back to the early 2000s and was listening to Not For Threes and Double Figure again.

'CLOCK' is where the band settle down into their strengths: surging and retreating beats and synths, pulsing along like sinewaves. 'The Bee' is a mix of slightly hip-hopped beats, mild guitars, and rich and hearty basslines. Oddly, it sounds like an instrumental track by a different band, rather than a track by a band that never uses vocals. It's followed up by the appropriately sweet 'Melifer', with its honeyed clouds of chiming synths and puffy, muted bass. And of course a dash of clicking percussion.

'Yu Mountain' is another big, pounding song, with nice metallic percussion and a weirdly warbling bassline. On the other end of the spectrum is 'Reeling Spiders', which features this wonderful, inwardly crumbling synth filigree for its first half. And closer 'Wen' has delightful layers of melody bubbling past each other before it tinkles away to nothing.

But there are a handful of relatively bland tracks as well, such as 'Lambswood' and 'Saladore', that go back to that more generic electro sound, something that any number of bands could have produced back in the 90s. And since these weaker tracks seem to be backloaded, the album leaves a poorer impression than it should.

To be fair, this is generally quite good stuff, but it's also nothing you haven't heard before if you've been following the band for any length of time. If they're new to you, this is a fine place to start, as it does include plenty of the distinctiveness that makes Plaid, Plaid. But no groundbreaking, mindblowing tunes have come out of this effort. This is clearly the work of a couple veteran musicians who are comfortable with themselves and their sound, and don't feel the need to pull any stunts to impress anyone. If you go into it knowing all that, this is worth a listen.

#electronic music #idm #downtempo #ambient music #plaid #warp #2016 #2010s #2010s electronic #pitchfork #headphone commute #resident advisor #pop matters #exclaim!#igloo magazine #treble #soundblab #review

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s-c-i-guy · 7 years ago

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Troubled Times for Alternatives to Einstein’s Theory of Gravity

New observations of extreme astrophysical systems have “brutally and pitilessly murdered” attempts to replace Einstein’s general theory of relativity.

Miguel Zumalacárregui knows what it feels like when theories die. In September 2017, he was at the Institute for Theoretical Physics in Saclay, near Paris, to speak at a meeting about dark energy and modified gravity. The official news had not yet broken about an epochal astronomical measurement — the detection, by gravitational wave detectors as well as many other telescopes, of a collision between two neutron stars — but a controversial tweet had lit a firestorm of rumor in the astronomical community, and excited researchers were discussing the discovery in hushed tones.

Zumalacárregui, a theoretical physicist at the Berkeley Center for Cosmological Physics, had been studying how the discovery of a neutron-star collision would affect so-called “alternative” theories of gravity. These theories attempt to overcome what many researchers consider to be two enormous problems with our understanding of the universe. Observations going back decades have shown that the universe appears to be filled with unseen particles — dark matter — as well as an anti-gravitational force called dark energy. Alternative theories of gravity attempt to eliminate the need for these phantasms by modifying the force of gravity in such a way that it properly describes all known observations — no dark stuff required.

At the meeting, Zumalacárregui joked to his audience about the perils of combining science and Twitter, and then explained what the consequences would be if the rumors were true. Many researchers knew that the merger would be a big deal, but a lot of them simply “hadn’t understood their theories were on the brink of demise,” he later wrote in an email. In Saclay, he read them the last rites. “That conference was like a funeral where we were breaking the news to some attendees.”

The neutron-star collision was just the beginning. New data in the months since that discovery have made life increasingly difficult for the proponents of many of the modified-gravity theories that remain. Astronomers have analyzed extreme astronomical systems that contain spinning neutron stars, or pulsars, to look for discrepancies between their motion and the predictions of general relativity — discrepancies that some theories of alternative gravity anticipate. These pulsar systems let astronomers probe gravity on a new scale and with new precision. And with each new observation, these alternative theories of gravity are having an increasingly hard time solving the problems they were invented for. Researchers “have to sweat some more trying to get new physics,” said Anne Archibald, an astrophysicist at the University of Amsterdam.

Searching for Vulcan

Confounding observations have a way of leading astronomers to desperate explanations. On the afternoon of March 26, 1859, Edmond Lescarbault, a young doctor and amateur astronomer in Orgères-en-Beauce, a small village south of Paris, had a break between patients. He rushed to a tiny homemade observatory on the roof of his stone barn. With the help of his telescope, he spotted an unknown round object moving across the face of the sun.

He quickly sent news of this discovery to Urbain Le Verrier, the world’s leading astronomer at the time. Le Verrier had been trying to account for an oddity in the movement of the planet Mercury. All other planets orbit the sun in perfect accord with Isaac Newton’s laws of motion and gravitation, but Mercury appeared to advance a tiny amount with each orbit, a phenomenon known as perihelion precession. Le Verrier was certain that there had to be an invisible “dark” planet tugging on Mercury. Lescarbault’s observation of a dark spot transiting the sun appeared to show that the planet, which Le Verrier named Vulcan, was real.

It was not. Lescarbault’s sightings were never confirmed, and the perihelion precession of Mercury remained a puzzle for nearly six more decades. Then Einstein developed his theory of general relativity, which straightforwardly predicted that Mercury should behave the way it does.

In Le Verrier’s impulse to explain puzzling observations by introducing a heretofore hidden object, some modern-day researchers see parallels to the story of dark matter and dark energy. For decades, astronomers have noticed that the behavior of galaxies and galaxy clusters doesn’t seem to fit the predictions of general relativity. Dark matter is one way to explain that behavior. Likewise, the accelerating expansion of the universe can be thought of as being powered by a dark energy.

All attempts to directly detect dark matter and dark energy have failed, however. That fact “kind of leaves a bad taste in some people’s mouths, almost like the fictional planet Vulcan,” said Leo Stein, a theoretical physicist at the California Institute of Technology. “Maybe we’re going about it all wrong?”

For any alternative theory of gravity to work, it has to not only do away with dark matter and dark energy, but also reproduce the predictions of general relativity in all the standard contexts. “The business of alternative gravity theories is a messy one,” Archibald said. Some would-be replacements for general relativity, like string theory and loop quantum gravity, don’t offer testable predictions. Others “make predictions that are spectacularly wrong, so the theorists have to devise some kind of a screening mechanism to hide the wrong prediction on scales we can actually test,” she said.

The best-known alternative gravity theories are known as modified Newtonian dynamics, commonly abbreviated to MOND. MOND-type theories attempt to do away with dark matter by tweaking our definition of gravity. Astronomers have long observed that the gravitational force due to ordinary matter doesn’t appear to be sufficient to keep rapidly moving stars inside their galaxies. The gravitational pull of dark matter is assumed to make up the difference. But according to MOND, there are simply two kinds of gravity. In regions where the force of gravity is strong, bodies obey Newton’s law of gravity, which states that the gravitational force between two objects decreases in proportion to the square of the distance that separates them. But in environments of extremely weak gravity — like the outer parts of a galaxy — MOND suggests that another type of gravity is in play. This gravity decreases more slowly with distance, which means that it doesn’t weaken as much. “The idea is to make gravity stronger when it should be weaker, like at the outskirts of a galaxy,” Zumalacárregui said.

Then there is TeVeS (tensor-vector-scalar), MOND’s relativistic cousin. While MOND is a modification of Newtonian gravity, TeVeS is an attempt to take the general idea of MOND and make it into a full mathematical theory that can be applied to the universe as a whole — not just to relatively small objects like solar systems and galaxies. It also explains the rotation curves of galaxies by making gravity stronger on their outskirts. But TeVeS does so by augmenting gravity with “scalar” and “vector” fields that “essentially amplify gravity,” said Fabian Schmidt, a cosmologist at the Max Planck Institute for Astrophysics in Garching, Germany. A scalar field is like the temperature throughout the atmosphere: At every point it has a numerical value but no direction. A vector field, by contrast, is like the wind: It has both a value (the wind speed) and a direction.

There are also so-called Galileon theories — part of a class of theories called Horndeski and beyond-Horndeski — which attempt to get rid of dark energy. These modifications of general relativity also introduce a scalar field. There are many of these theories (Brans-Dicke theory, dilaton theories, chameleon theories and quintessence are just some of them), and their predictions vary wildly among models. But they all change the expansion of the universe and tweak the force of gravity. Horndeski theory was first put forward by Gregory Horndeski in 1974, but the wider physics community took note of it only around 2010. By then, Zumalacárregui said, “Gregory Horndeski [had] quit science and [become] a painter in New Mexico.”

There are also stand-alone theories, like that of physicist Erik Verlinde. According to his theory, the laws of gravity arise naturally from the laws of thermodynamics just like “the way waves emerge from the molecules of water in the ocean,” Zumalacárregui said. Verlinde wrote in an email that his ideas are not an “alternative theory” of gravity, but “the next theory of gravity that contains and transcends Einstein’s general relativity.” But he is still developing his ideas. “My impression is that the theory is still not sufficiently worked out to permit the kind of precision tests we carry out,” Archibald said. It’s built on “fancy words,” Zumalacárregui said, “but no mathematical framework to compute predictions and do solid tests.”

The predictions made by other theories differ in some way from those of general relativity. Yet these differences can be subtle, which makes them incredibly difficult to find.

Consider the neutron-star merger. At the same time that the Laser Interferometer Gravitational-Wave Observatory (LIGO) spotted the gravitational waves emanating from the event, the space-based Fermi satellite spotted a gamma ray burst from the same location. The two signals had traveled across the universe for 130 million years before arriving at Earth just 1.7 seconds apart.

These nearly simultaneous observations “brutally and pitilessly murdered” TeVeS theories, said Paulo Freire, an astrophysicist at the Max Planck Institute for Radio Astronomy in Bonn, Germany. “Gravity and gravitational waves propagate at the speed of light, with extremely high precision — which is not at all what was predicted by those [alternative] theories.”

The same fate overtook some Galileon theories that add an extra scalar field to explain the universe’s accelerated expansion. These also predict that gravitational waves propagate more slowly than light. The neutron-star merger killed those off too, Schmidt said.

Further limits come from new pulsar systems. In 2013, Archibald and her colleagues found an unusual triple system: a pulsar and a white dwarf that orbit one another, with a second white dwarf orbiting the pair. These three objects exist in a space smaller than Earth’s orbit around the sun. The tight setting, Archibald said, offers ideal conditions for testing a crucial aspect of general relativity called the strong equivalence principle, which states that very dense strong-gravity objects such as neutron stars or black holes “fall” in the same way when placed in a gravitational field. (On Earth, the more familiar weak equivalence principle states that, if we ignore air resistance, a feather and a brick will fall at the same rate.)

The triple system makes it possible to check whether the pulsar and the inner white dwarf fall exactly the same way in the gravity of the outer white dwarf. Alternative-gravity theories assume that the scalar field generated in the pulsar should bend space-time in a much more extreme way than the white dwarf does. The two wouldn’t fall in a similar manner, leading to a violation of the strong equivalence principle and, with it, general relativity.

Over the past five years, Archibald and her team have recorded 27,000 measurements of the pulsar’s position as it orbits the other two stars. While the project is still a work in progress, it looks as though the results will be in total agreement with Einstein, Archibald said. “We can say that the degree to which the pulsar behaves abnormally is at most a few parts in a million. For an object with such strong gravity to still follow Einstein’s predictions so well, if there is one of these scalar fields, it has to have a really tiny effect.”

The test, which should be published soon, will put the best constraints yet on a whole group of alternative gravity theories, she added. If a theory only works with some additional scalar field, then the field should change the behavior of the pulsar. “We have such sensitive tests of general relativity that they need to somehow hide the theory’s new behavior in the solar system and in pulsar systems like ours,” Archibald said.

The data from another pulsar system dubbed the double pulsar, meanwhile, was originally supposed to eliminate the TeVeS theories. Detected in 2003, the double pulsar was until recently the only binary neutron-star system where both neutron stars were pulsars. Freire and his colleagues have already confirmed that the double pulsar’s behavior is perfectly in line with general relativity. Right before LIGO’s October announcement of a neutron-star merger, the researchers were going to publish a paper that would kill off TeVeS. But LIGO did the job for them, Freire said. “We need not go through that anymore.”

Slippery Survivors

A few theories have survived the LIGO blow — and will probably survive the upcoming pulsar data, Zumalacárregui said. There are some Horndeski and beyond-Horndeski theories that do not change the speed of gravitational waves. Then there are so-called massive gravity theories. Ordinarily, physicists assume that the particle associated with the force of gravity — the graviton — has no mass. In these theories, the graviton has a very small but nonzero mass. The neutron-star merger puts tough limits on these theories, Zumalacárregui said, since a massive graviton would travel more slowly than light. But in some theories the mass is assumed to be extremely small, at least 20 orders of magnitude lower than the neutrino’s, which means that the graviton would still move at nearly the speed of light.

There are a few other less well-known survivors, some of which are important to keep exploring, Archibald said, as long as dark matter and dark energy remain elusive. “Dark energy might be our only observational clue pointing to a new and better theory of gravity — or it might be a mysterious fluid with strange properties, and nothing to do with gravity at all,” she said.

Still, killing off theories is simply how science is supposed to work, argue researchers who have been exploring alternative gravity theories. “This is what we do all the time, put forward a working hypothesis and test it,” said Enrico Barausse of the Astrophysics Institute of Paris, who has worked on MOND-like theories. “99.9 percent of the time you rule out the hypothesis; the remaining 0.1 percent of the time you win the Nobel Prize.”

Zumalacárregui, who has also worked on these theories, was “sad at first” when he realized that the neutron star merger detection had proven Galileon theories wrong, but ultimately “very relieved it happened sooner rather than later,” he said. LIGO had been just about to close down for 18 months to upgrade the detector. “If the event had been a bit later, I would still be working on a wrong theory.”

So what’s next for general relativity and modified-gravity theories? “That question keeps me up at night more than I’d like,” Zumalacárregui said. “The good news is that we have narrowed our scope by a lot, and we can try to understand the few survivors much better.”

Schmidt thinks it’s necessary to measure the laws of gravity on large scales as directly as possible, using ongoing and future large galaxy surveys. “For example, we can compare the effect of gravity on light bending as well as galaxy velocities, typically predicted to be different in modified-gravity theories,” he said. Researchers also hope that future telescopes such as the Square Kilometer Array will discover more pulsar systems and provide better accuracy in pulsar timing to further improve gravity tests. And a space-based replacement for LIGO called LISA will study gravitational waves with exquisite accuracy — if indeed it launches as planned in the mid-2030s. “If that does not see any deviations from general relativity, I don’t know what will,” said Barausse.

But many physicists agree that it will take a long time to get rid of most alternative gravity models. Theorists have dozens of alternative gravity theories that could potentially explain dark matter and dark energy, Freire said. Some of these theories can’t make testable predictions, Archibald said, and many “have a parameter, a ‘knob’ you can turn to make them pass any test you like,” she said. But at some point, said Nicolas Yunes, a physicist at Montana State University, “this gets silly and Occam’s razor wins.”

Still, “fundamentally we know that general relativity is wrong,” Stein said. “At the very core there must be some breakdown” at the quantum level. “Maybe we won’t see it from astronomical observations … but we owe it to ourselves, as empirical scientists, to check whether or not our mathematical models are working at these scales.”

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