Sci­en­tists fer­vently tune in to sound­track of the cos­mos

A year af­ter their dis­cov­ery, ob­ser­va­tory re­searchers are lis­ten­ing to grav­i­ta­tional waves as as­tro­physics lit­er­ally evolves into a global en­deavor

The Washington Post Sunday - - POLITICS & THE NATION - BY JOEL ACHENBACH joel.achenbach@wash­post.com

liv­ingston, la. — The speed limit on the LIGO ac­cess road is 10 mph, which is pre­pos­ter­ously slow, par­tic­u­larly af­ter you’ve spent the past hour hurtling across the bayou coun­try on el­e­vated free­ways. You have to creep to­ward the guard booth. The sci­en­tists and en­gi­neers don’t care how fast you drive; it’s the brak­ing that’s the prob­lem. De­cel­er­a­tion ex­erts a force on the road that can throw off exquisitely sen­si­tive in­stru­ments nearby.

This is ba­sic physics, and it’s a headache for LIGO, the Laser In­ter­fer­om­e­ter Grav­i­ta­tional-wave Ob­ser­va­tory.

True story: A few years back, Am­ber Stu­ver, a physi­cist, was sit­ting in the LIGO con­trol room on a quiet day, with no seis­mic ac­tiv­ity, no wind. The lasers were func­tion­ing per­fectly. Sud­denly, ev­ery­thing went hay­wire.

“What just hap­pened?” Stu­ver asked her co-work­ers.

“FedEx guy,” some­one an­swered.

The FedEx guy! Comes ev­ery day at 4:30 to the load­ing dock, im­pa­tient driver, hit the brakes too hard — and ren­dered deaf an in­stru­ment de­signed to hear grav­i­ta­tional waves from ex­plod­ing stars and black-hole col­li­sions bil­lions of light-years away.

The point is that LIGO is a del­i­cate busi­ness.

One year ago, LIGO sci­en­tists gath­ered in Wash­ing­ton to an­nounce their his­toric dis­cov­ery of grav­i­ta­tional waves — rip­ples through the fab­ric of space and time, some­thing the­o­rized by Al­bert Ein­stein ex­actly a cen­tury ear­lier but dis­may­ingly elu­sive. The waves in that ini­tial dis­cov­ery came from the unimag­in­ably vi­o­lent merger of two black holes in a dis­tant precinct of the uni­verse.

Now sci­en­tists at LIGO think they’re on the verge of a string of cos­mic break­throughs, but they also have a new set of con­cerns, and they don’t in­volve the FedEx guy. The ques­tion is: What’s go­ing to hap­pen to sci­ence in the Age of Trump?

LIGO in­volves, ac­cord­ing to its own count, 1,006 sci­en­tists from 83 dif­fer­ent in­sti­tu­tions in 15 na­tions. A num­ber of stu­dents who work on LIGO-re­lated re­search are af­fected by the Trump ad­min­is­tra­tion’s en­try ban, ac­cord­ing to LIGO’s chief spokes­woman, Gabriela González, a physi­cist at nearby Louisiana State University.

“We are very con­cerned,” González said in a phone in­ter­view. “They are part of our sci­en­tific work­force, and now at this time they can­not travel abroad.”

This is a new sci­en­tific field, and it will ben­e­fit dra­mat­i­cally from ob­ser­va­to­ries be­ing built in Italy, Ja­pan and In­dia. The Euro­pean Space Agency is also pre­par­ing a space-based grav­i­ta­tional-wave de­tec­tor, called LISA.

González em­pha­sized the need for a global network of de­tec­tors. This is not a feel-good con­cept but a sim­ple func­tion of ge­om­e­try. De­tec­tors spaced far apart can tri­an­gu­late the ori­gin of a grav­i­ta­tional wave. This is a global project, be­cause sci­en­tists want a truly planet-size network to sharpen their de­tec­tion skills.

Be­cause LIGO has two de­tec­tors, both in North Amer­ica, sci­en­tists have only an ap­prox­i­mate no­tion of where any par­tic­u­lar wave comes from. They can point to a gen­eral re­gion of the sky, ob­long in shape, and say it came from over that­away.

“The big­ger the tri­an­gle, the bet­ter the pre­ci­sion,” González said. “We need the network.”

Fund­ing is an­other con­cern, though LIGO would seem bet­ter po­si­tioned than many other sci­en­tific en­deav­ors, par­tic­u­larly cli­mate-change and so­cial-sci­ence re­search, which are likely tar­gets for cuts by the Trump ad­min­is­tra­tion and the Repub­li­can ma­jor­ity in Congress. Ba­sic sci­ence re­search, how­ever, has tra­di­tion­ally en­joyed bi­par­ti­san sup­port.

LIGO is funded by the Na­tional Sci­ence Foun­da­tion, an in­de­pen­dent agency of the fed­eral gov­ern­ment with an annual bud­get of about $7.5 bil­lion. In the past two decades, NSF has spent about $1.1 bil­lion on LIGO, which is op­er­ated by Cal­tech and MIT and in­cludes a sec­ond site, the LIGO Han­ford Ob­ser­va­tory in east­ern Wash­ing­ton.

The chair­man of the House Sci­ence Com­mit­tee, La­mar Smith (R-Tex.), has sup­ported the project, ac­cord­ing to com­mit­tee spokes­woman Kristina Baum.

She wrote in an email, “The Chair­man’s pri­or­i­ties in­clude en­sur­ing more NSF fund­ing is di­rected to­wards the hard sciences and ground­break­ing re­search like grav­i­ta­tional waves, and less fund­ing to friv­o­lous or mar­ginal projects.”

LIGO cer­tainly meets the def­i­ni­tion of hard sci­ence.

There’s only one stop­light in Liv­ingston, a small town about an hour north of New Or­leans. If you look closely, you’ll see a tiny sign, with an ar­row, say­ing “LIGO.” It’s easy to miss next to the three bill­boards ad­ver­tis­ing a per­sonal-in­jury at­tor­ney, a $5,000 re­ward for tips to Crime Stop­pers, and “Top Dol­lar Paid” for gold and guns at a pawn­shop.

But if you head west a cou­ple of hun­dred yards, and then turn north at the Fire­works Ware­house, and drive a few miles on a wind­ing coun­try road, you’ll even­tu­ally reach the place where the the­ory of grav­i­ta­tional waves be­came a re­al­ity.

LIGO is, in some ways, an in­cred­i­bly im­prob­a­ble en­ter­prise be­cause of its phys­i­cal scale and es­o­teric sci­en­tific am­bi­tion. There is no ob­vi­ous ap­pli­ca­tion for the knowl­edge gained. The cost of the project could eas­ily have led to a kind of grav­i­ta­tional col­lapse end­ing in obliv­ion. And although it had a firm the­o­ret­i­cal foun­da­tion — Who would bet against Ein­stein? — it re­quired lev­els of en­gi­neer­ing never be­fore at­tempted.

The two ob­ser­va­to­ries in Louisiana and Wash­ing­ton state had to be built in re­mote, seis­mi­cally sta­ble lo­ca­tions. The dom­i­nant fea­ture of each fa­cil­ity is the pair of 2.5-mile-long beam lines, set per­pen­dic­u­larly. These are tubes in which laser beams pass through an al­most per­fect vac­uum.

“We had to cor­rect for the cur­va­ture of the Earth,” Stu­ver said, stand­ing on a bridge over­look­ing one of the beam line tubes as it re­ceded into the piney woods — tim­ber land owned pri­mar­ily by Wey­er­haeuser. “From the cor­ner there to the end of the arm, the Earth curves down away a lit­tle bit more than four feet.”

A re­porter drove a rental car the length of the arm, with Stu­ver serv­ing as nar­ra­tor. The beam line is en­cased in heavy con­crete. Stu­ver said that so few atoms and mol­e­cules re­main in the vac­uum tubes that if you could gather them all up, from the en­tire 2.5-mile length, and com­press them to nor­mal at­mo­spheric pres­sure, they would amount to one thim­ble­ful of air.

Hunt­ing stands are nearby in the woods, but they point away from the beam lines. The sci­en­tists met with lo­cal hunt­ing clubs and made a sim­ple re­quest: Don’t shoot the ob­ser­va­tory.

The es­sen­tial con­cept of LIGO is that a grav­i­ta­tional wave, when it passes through Liv­ingston, will stretch one arm while con­tract­ing the other that runs at a 90-de­gree an­gle. Space it­self will change di­men­sions. Two arms nor­mally of iden­ti­cal length will sud­denly be slightly mis­matched. This ef­fect, how­ever, is smaller than the width of an atom.

That’s where the lasers come in. A laser beam is split into two beams, one for each arm. The beams travel the length of the arms and bounce off mir­rors at the end. They cir­cu­late hun­dreds of times in the arms be­fore fi­nally re­con­verg­ing at the cor­ner where the arms meet.

If there’s no grav­i­ta­tional wave rolling through town, the wave­lengths of the beams will con­tinue to line up per­fectly. But if, say, a cou­ple of black holes have col­lided, and the rip­ple of the event passes through Earth, the shift in the laser wave­lengths can re­veal the sig­na­ture of that dis­tant cat­a­clysm.

The first big run of LIGO, from 2002 to 2010, had yielded bup­kis. The ob­ser­va­tory just wasn’t sen­si­tive enough. But the ex­per­i­ment got some up­grades, and sud­denly the uni­verse be­came au­di­ble. At pre­cisely 4:51 a.m. CDT on the morn­ing of Sept. 14, 2015, the Liv­ingston de­tec­tor picked up a sig­nal — a hum, build­ing in in­ten­sity and end­ing in a chirp.

A frac­tion of a sec­ond later, the de­tec­tor 1,865 miles away in Han­ford, Wash., picked up the same sig­nal — and in the process con­firmed that grav­i­ta­tional waves move at the speed of light. The sig­nal fit pre­cisely with the the­o­ret­i­cal mod­els for what hap­pens when black holes col­lide.

A month later, an­other ap­par­ent grav­i­ta­tional wave passed through — though sci­en­tists can’t be ab­so­lutely sure it wasn’t caused by some ter­res­trial noise.

“I have an 87 per­cent con­fi­dence that this is a grav­i­ta­tional wave from an as­tro­phys­i­cal source,” Stu­ver said. That sounds pretty good, but sci­en­tists don’t con­sider an 87 per­cent prob­a­bil­ity very ro­bust.

In De­cem­ber 2015, a third event hap­pened, and that one passed the con­fi­dence test. Thus dur­ing a roughly four-month de­tec­tion run, LIGO picked up two cer­tain events and one pos­si­ble event.

LIGO sci­en­tists were de­lib­er­ate in an­nounc­ing their dis­cov­ery. First they had to make sure that some­one had not pro­grammed a fake sig­nal in the de­tec­tors as a way of test­ing the in­stru­ments. Then they had to pre­pare a sci­en­tific pa­per with more than 1,000 co-au­thors. They fi­nally booked a room at the Na­tional Press Club in Wash­ing­ton and flew in the pioneers of LIGO for the Feb. 11, 2016, news con­fer­ence.

Here in Liv­ingston, life changed. LIGO had been around for years, but many lo­cals didn’t know any­thing about it. They may have heard about it from schoolkids who went to the fa­cil­ity on field trips (there is an im­pres­sive sci­ence cen­ter with ex­hibits on lasers, grav­ity and ba­sic physics). But at the first open house af­ter the an­nounce­ment, 1,292 peo­ple showed up to see what the fuss was about.

“For the first time in my life, I saw peo­ple stand­ing in line for a sci­ence tour as though it was a ride at an amuse­ment park,” Stu­ver said.

Un­til LIGO came along, in­for­ma­tion about the uni­verse came al­most ex­clu­sively from wave­lengths of light in the elec­tro­mag­netic spec­trum. That in­cludes op­ti­cal, X-ray, gamma-ray and in­frared tele­scopes. But grav­i­ta­tional waves carry in­for­ma­tion, too.

“This is like Galileo turn­ing the tele­scope to the sky for the very first time,” Stu­ver said.

At a con­gres­sional hear­ing last year be­fore the House Sci­ence Com­mit­tee, Smith asked a panel of LIGO lead­ers, “What are the prac­ti­cal con­se­quences of — or, prac­ti­cal ap­pli­ca­tions of grav­i­ta­tional waves?”

LIGO sci­en­tists an­swered by say­ing that the ex­per­i­ment has al­ready led to tech­no­log­i­cal ad­vances in “vi­bra­tion iso­la­tion” and “laser sta­bi­liza­tion,” as well as pre­ci­sion time­keep­ing. This is also a train­ing ground for sci­en­tists mov­ing into other are­nas.

But no one re­ally sells LIGO on prac­ti­cal grounds. The main sell­ing point: It’s knowl­edge for its own sake. LIGO probes the dark­ness, and re­veals hid­den and uni­ver­sal truths.

LIGO LAB­O­RA­TORY/REUTERS

ABOVE: A tech­ni­cian with the Laser In­ter­fer­om­e­ter Grav­i­ta­tional-wave Ob­ser­va­tory in­stalls a mode cleaner tube baf­fle used to con­trol stray light as part of the Ad­vanced LIGO aux­il­iary op­tics sys­tem in 2010.

MAX BECHERER/PO­LARIS IMAGES FOR THE WASH­ING­TON POST

LEFT: Am­ber Stu­ver, a physi­cist with LIGO, stands in front of the fa­cil­ity’s X arm beam tube last week. Stu­ver is part of a team of sci­en­tists mea­sur­ing grav­i­ta­tional waves at the fa­cil­ity in Liv­ingston, La.

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