Ein­stein con­tin­ues to make waves

‘Why is it,’ Ein­stein asked in March 1944, ‘that no­body un­der­stands me, and ev­ery­body likes me?’ Jonathan Gor­nall ex­plores the great sci­en­tist’s legacy in light of the re­cent dis­cov­ery of grav­i­ta­tional waves

The National - News - The Review - - Front Page - Jonathan Gor­nall is a reg­u­lar con­trib­u­tor to The Re­view.

As the new mil­len­nium loomed, a Gallup poll com­mis­sioned by CNN and USA To­day found that Amer­i­cans ad­mired four peo­ple from the 20th cen­tury above all oth­ers.

The first three came as lit­tle sur­prise. Mother Teresa, Martin Luther King, Jr and John F Kennedy – most peo­ple could prob­a­bly sum­marise their con­tri­bu­tions to the world.

But at num­ber four in the list was Al­bert Ein­stein – a name as in­stantly recog­nis­able as his car­toon­ish, “mad sci­en­tist” im­age and a by­word for ge­nius in pop­u­lar cul­ture. But what did Ein­stein achieve that so many peo­ple ad­mired? Some may have in­voked his the­o­ries of rel­a­tiv­ity, or the T-shirt-friendly equa­tion E = mc2.

But how many could have ex­plained them in any depth, or known that his 1921 No­bel Prize was un­re­lated, that it was awarded for “his ser­vices to The­o­ret­i­cal Physics, and es­pe­cially for his dis­cov­ery of the law of the pho­to­elec­tric ef­fect”?

In an in­ter­view in The New York Times in March 1944, Ein­stein asked: “Why is it that no­body un­der­stands me, and ev­ery­body likes me?”

The Gallup sur­vey is ev­i­dence of what can be termed “the Ein­stein The­ory of Gulli­bil­ity”: that when it comes to that slip­pery thing we call ge­nius, most of us hap­pily ac­cept that we have ab­so­lutely no chance of un­der­stand­ing what that ge­nius en­tails.

More than 60 years af­ter his death at the age of 76, Ein­stein is in the head­lines once again. His name and work have been con­jured up by sci­en­tists and jour­nal­ists in seek­ing the great man’s post­hu­mous en­dorse­ment for what has been de­scribed by some as “the most im­por­tant sci­en­tific break­through of the cen­tury”.

On Fe­bru­ary 11, hun­dreds of sci­en­tists work­ing on a decades-long, multi­bil­lion-dol­lar, multi­na­tional col­lab­o­ra­tive pro­ject in the United States col­lec­tively an­nounced they had de­tected “rip­ples in the fab­ric of space­time called grav­i­ta­tional waves, ar­riv­ing at the Earth from a cat­a­clysmic event in the dis­tant uni­verse”.

The event had been long pre­dicted but never wit­nessed: a com­ing to­gether of two black holes, 1.3 bil­lion light years away from Earth, which had been slowly or­bit­ing and draw­ing in­ex­orably closer for bil­lions of years.

Ac­cord­ing to the Laser In­ter­fer­om­e­ter Grav­i­ta­tional-Wave Ob­ser­va­tory (Ligo) Sci­en­tific Col­lab­o­ra­tion, in the fi­nal few min­utes this dance ac­cel­er­ated dra­mat­i­cally un­til, “dur­ing the fi­nal frac­tion of a se­cond, the two black holes col­lide into each other at nearly one-half the speed of light and form a sin­gle, more mas­sive, black hole”.

The re­sult­ing re­lease of en­ergy was emit­ted as a burst of grav­i­ta­tional waves, and it was th­ese that Ligo ob­served. The de­tec­tion of th­ese faint waves on Earth up to 1.3bn years later – an ob­ser­va­tion made on Septem­ber 14 last year – “con­firms a ma­jor pre­dic­tion of Al­bert Ein­stein’s 1915 gen­eral the­ory of rel­a­tiv­ity and opens an un­prece­dented new win­dow onto the cos­mos”, said Ligo. “The field of grav­i­ta­tional wave as­tron­omy is now a re­al­ity.”

Con­ve­niently, the dis­cov­ery hap­pened ex­actly “100 years af­ter Ein­stein’s pre­dic­tion”.

It was, said the di­rec­tor of the White House Of­fice of Sci­ence and Tech­nol­ogy Pol­icy, which has in­vested US$1 bil­lion (Dh3.67bn) in the pro­ject, “one of his­tory’s great­est sci­en­tific dis­cov­er­ies”. Cue unquestioning cel­e­bra­tory head­lines around the world. In the en­su­ing ex­cite­ment, even US pres­i­dent Barack Obama found time to Tweet “Ein­stein was right!”.

Only, he wasn’t. Ein­stein be­lieved in nei­ther grav­i­ta­tional waves nor black holes.

While there are few the­o­ret­i­cal or ex­per­i­men­tal physi­cists who would dis­pute Ein­stein’s im­mense sig­nif­i­cance to their field – his 1915 gen­eral the­ory of rel­a­tiv­ity nailed grav­ity and is the foun­da­tion of all mod­ern astro­physics – a hand­ful of sci­en­tists out­side the Ligo magic cir­cle have ex­pressed scep­ti­cism about the dis­cov­ery.

Dr Natalia Kir­iushcheva, a the­o­ret­i­cal and com­pu­ta­tional physi­cist at the Univer­sity of Western On­tario (UWO), Canada, says that while it was Ein­stein who ini­ti­ated the grav­i­ta­tional waves the­ory in a pa­per in June 1916, it was an ad­den­dum to his the­ory of gen­eral rel­a­tiv­ity and by 1936, he had con­cluded that such things did not ex­ist. Fur­ther­more – as a pa­per pub­lished by Ein­stein in the An­nals of Math­e­mat­ics in Oc­to­ber, 1939 made clear, he also re­jected the pos­si­bil­ity of black holes.

Re­gard­less, on news of the dis­cov­ery last month, Rainer Weiss, an MIT (Mas­sachusetts In­sti­tute of Tech­nol­ogy) physics pro­fes­sor, who was among those who pro­posed the Ligo pro­ject in the 1980s, said: “It would have been won­der­ful to watch Ein­stein’s face had we been able to tell him.”

It surely would, says Dr Kir­iushcheva. Were Ein­stein alive to­day, she says: “I think he would be very scep­ti­cal about this dis­cov­ery, and would an­a­lyse very, very care­fully what they have been do­ing.”

In Ein­stein’s ab­sence, Dr Kir­iushcheva and Sergei Kuzmin, a UWO maths pro­fes­sor who shares her scep­ti­cism, have been do­ing just that.

In the process, they are go­ing up against an in­sti­tu­tional be­he­moth – some­thing Ein­stein, a sin­gu­lar in­di­vid­ual who ab­horred “herd na­ture”, would doubt­less have ap­proved of.

Founded in 1997 for the sole pur­pose of prov­ing the ex­is­tence of and de­tect­ing grav­i­ta­tional waves, Ligo em­braces about 1,500 sci­en­tists from dozens of in­sti­tu­tions across 15 coun­tries, in­clud­ing the US, Bri­tain, Korea, Aus­tralia, Ger­many, In­dia and Rus­sia.

Proof of the bank­able value of the dis­cov­ery came on Fe­bru­ary 17, less than a week af­ter the an­nounce­ment, when the In­dian govern­ment gave the go-ahead to a four-year-old pro­posal to build In­dia’s own Ligo ob­ser­va­tory.

Nev­er­the­less, says Dr Kir­iushcheva, it is the job of sci­en­tists to be scep­ti­cal – and, she in­sists, there is plenty about the Ligo pro­ject that in­vites scep­ti­cism.

The Ligo Sci­en­tific Col­lab­o­ra­tion re­lies pri­mar­ily on two unique pieces of equip­ment more than 3,000 kilo­me­tres apart in the US: one in Liv­ingston, Louisiana, and the other up in the northwest, in Han­ford, Wash­ing­ton.

Each of th­ese iden­ti­cal “laser in­ter­fer­om­e­ters” con­sists of two 4km long tun­nels, set at 90 de­grees to each other. A laser beam is split and fired through the two tun­nels, bounc­ing off a mir­ror at the end and then back to a mir­ror at the start. The dis­tance each beam trav­els is pre­cisely the same – un­til, in the­ory, a pass­ing grav­i­ta­tional wave, minutely dis­tort­ing space as it passes at the speed of light, af­fects the length of first one and then the other.

On the re­peated cy­cle of this dis­tor­tion alone, the Ligo sci­en­tists claimed that they had not only de­tected grav­i­ta­tional waves for the first time, but that the waves had orig­i­nated from the never-be­fore-wit­nessed merger of two black holes, 1.3bn light years away from Earth – an event that hap­pened at about the same time as the first plants grew on Earth.

The dis­tance be­tween the two de­tec­tors meant that the wave was picked up by the Liv­ingston ob­ser­va­tory seven mil­lisec­onds be­fore its coun­ter­part in Han­ford, which gave the sci­en­tists a rough idea of the di­rec­tion in the uni­verse from which it orig­i­nated.

Now it re­mains only for the No­bel Foun­da­tion to fig­ure out who among the 1,500 in­hab­i­tants of the Ligo vil­lage should be awarded the next No­bel Prize for physics.

But, ac­cord­ing to the Ligo pa­per, the ob­ser­va­tions were made by the twin ob­ser­va­to­ries on Septem­ber 14, 2015. The prob­lem with this, says Dr Kir­iushcheva, is that this was four days be­fore the de­tec­tors be­gan their first “ob­serv­ing run”. There is no men­tion of this in the dis­cov­ery pa­per. Ligo’s twin ob­ser­va­to­ries, fit­ted with up­graded de­tec­tors, had un­der­gone a five-year re­build and, ac­cord­ing to the or­gan­i­sa­tion’s records, did not start their “first of­fi­cial ‘ob­serv­ing run’” un­til 8am on Septem­ber 18, 2015 – four days af­ter the his­toric de­tec­tion of grav­i­ta­tional waves.

In the weeks lead­ing up to the run, both in­ter­fer­om­e­ters had been “op­er­at­ing in en­gi­neer­ing mode” as tech­ni­cians had been “work[ing] to re­fine the in­stru­ment to pre­pare it for of­fi­cial data col­lec­tion du­ties”.

Surely this meant that, by Ligo’s own terms, op­ti­mal con­di­tions for the ex­per­i­ment were not in place when the waves were de­tected?

Not so, says Peter Shawhan, a pro­fes­sor at the Univer­sity of Mary­land and a Ligo spokesman.

“The last ac­tual ad­just­ments to the de­tec­tors were made on Septem­ber 11, so we have sta­ble, well-cal­i­brated data from Septem­ber 12 on­ward,” he told The Na­tional.

Ligo had “de­cided not to write about that de­tail” in the main pa­per but it was “de­scribed briefly” in a com­pan­ion pa­per – Char­ac­ter­i­sa­tion of tran­sient noise in Ad­vanced LIGO rel­e­vant to grav­i­ta­tional

wave sig­nal GW150914 – which went un­re­ported amid the global ac­claim. One de­tail that was men­tioned in the main pa­per, though only in pass­ing, was the cu­ri­ous fact that the his­toric de­tec­tion was made while Ligo’s com­pan­ion Virgo de­tec­tor, a col­lab­o­ra­tion be­tween the Ital­ian and French gov­ern­ments and lo­cated just out­side Pisa, was off­line, un­der­go­ing its own upgrade.

This seems re­mark­able: the whole point of hav­ing mul­ti­ple de­tec­tion cen­tres, as widely sep­a­rated as pos­si­ble, is to cor­rob­o­rate and in­crease con­fi­dence in any de­tec­tion.

“We have [our own] two widely-sep­a­rated Ligo de­tec­tors, and check­ing for con­sis­tency be­tween them is ab­so­lutely cru­cial for the analy­ses we do,” says Prof Shawhan.

“But you are right, we would have liked to have Virgo run­ning too, and see­ing the sig­nal in three de­tec­tors would give us even greater con­fi­dence.”

Yet it seems this wasn’t the only part of the global de­tec­tion sys­tem not in place when the grav­i­ta­tional waves were re­ported.

In a Septem­ber 18 press re­lease that an­nounced the start of the Ligo de­tec­tors’ first of­fi­cial ob­serv­ing run – four days af­ter ev­i­dence of grav­i­ta­tional waves was recorded – much was made of a world­wide net­work of con­ven­tional ob­ser­va­to­ries on standby to val­i­date any ap­par­ent de­tec­tion.

“To­day,” Ligo an­nounced, “the broader as­tro­nom­i­cal com­mu­nity has been added to the team.” This meant Ligo would “be able to no­tify any num­ber of 74 as­tro­nom­i­cal ob­ser­va­to­ries around the world, who have agreed to, at a mo­ment’s no­tice, point their tele­scopes to the sky in search of light sig­nals cor­re­spond­ing to pos­si­ble grav­i­ta­tional wave de­tec­tions”. But there was no men­tion of this net­work in the dis­cov­ery pa­per. The sim­ple rea­son, says Prof Shawhan, was, “as you guessed, on Septem­ber 14 we were not ready to promptly share an event can­di­date with the as­tronomers”.

He down­played the sig­nif­i­cance of tele­scopes in con­firm­ing Ligo de­tec­tions. “We would,” he says, “love it if the as­tronomers are able to find a coun­ter­part, but we do not nec­es­sar­ily ex­pect there to be a de­tectable coun­ter­part for ev­ery grav­i­ta­tional wave event.”

There are other black holes in the Ligo uni­verse, says Dr Kir­iushcheva and other sci­en­tists, who are rais­ing ques­tions about an event that took place five years ago, shortly be­fore the twin US de­tec­tors were closed for their upgrade.

On Septem­ber 16, 2010, a false sig­nal – a so­called “blind injection” – was fed into both the Ligo and Virgo sys­tems as part of an ex­er­cise to “test ... de­tec­tion ca­pa­bil­i­ties”. At the time, the vast ma­jor­ity of the hun­dreds of sci­en­tists work­ing on the equip­ment had no idea that they were be­ing fed a dummy sig­nal.

The truth was not re­vealed un­til March the fol­low­ing year, by which time sev­eral pa­pers about the sup­posed sen­sa­tional dis­cov­ery of grav­i­ta­tional waves were poised for pub­li­ca­tion.

“While the sci­en­tists were dis­ap­pointed that the dis­cov­ery was not real, the suc­cess of the anal­y­sis was a com­pelling demon­stra­tion of the col­lab­o­ra­tion’s readi­ness to de­tect grav­i­ta­tional waves,” Ligo re­ported at the time.

But take a look at the vi­su­al­i­sa­tion (www.ligo. org/news/ blind-injection.php) of the faked sig­nal, says Dr Kir­iushcheva, and com­pare it to the im­age ap­par­ently show­ing the col­li­sion of the twin black holes, seen on the se­cond page of the re­cently-pub­lished dis­cov­ery pa­per (tinyurl.com/ h3wkvmo).

“They look very, very sim­i­lar,” she says. “It means that they knew ex­actly what they wanted to get and this is sus­pi­cious for us: when you know what you want to get from sci­ence, usu­ally you can get it.”

The ap­par­ent sim­i­lar­ity is more cu­ri­ous be­cause the faked event pur­ported to show not a col­li­sion be­tween two black holes, but the grav­i­ta­tional waves cre­ated by a neu­tron star spi­ralling into a black hole. The sig­nals ap­pear so sim­i­lar, in fact, that Dr Kir­iushcheva ques­tions whether the “true” sig­nal might ac­tu­ally have been an echo of the fake, “stored in the com­puter sys­tem from when they turned off the equip­ment five years be­fore”.

Prof Shawhan ad­mits that “most of us who saw the sig­nal early on Septem­ber 14 [ last year] as­sumed that it must be a blind injection since it was so beau­ti­ful”.

But “the blind injection team had not started the ac­tive pe­riod for that yet, and dou­ble-checks of all chan­nels con­firmed that there was no injection, ei­ther in­ten­tional or un­in­ten­tional”.

Be­sides, he says, al­though the two im­ages “do look visu­ally sim­i­lar, if you look closely you can see that the timescales are dif­fer­ent”.

The fake sig­nal from 2010 rises from a fre­quency of about 90 to 256 hertz in 0.25 sec­onds, a jump that takes the Septem­ber 2015 sig­nal only about only 0.02 sec­onds to achieve. That, he says, “tells you that the 2015 event cor­re­sponds to a bi­nary [event] with larger masses”. For Dr Kir­iushcheva and her col­leagues, per­haps the big­gest ques­tion mark hang­ing over the Ligo find­ings is that for any sci­en­tific ex­per­i­ment to have full cred­i­bil­ity, its re­sults must be in­de­pen­dently re­peat­able – clearly im­pos­si­ble when only Ligo and its sci­en­tists have ac­cess to the nec­es­sary fund­ing and equip­ment.

Prof Shawhan says that “the re­sults have been repli­cated in some sense; al­though it may look like one re­sult from the out­side … we rely on two in­de­pen­dent de­tec­tors each ob­serv­ing the same event in a con­sis­tent way.

“We also have found the event us­ing mul­ti­ple in­de­pen­dent data anal­y­sis al­go­rithms ex­e­cuted by dif­fer­ent peo­ple within our col­lab­o­ra­tion … this gives us the con­fi­dence to claim that we have un­am­bigu­ously de­tected a grav­i­ta­tional wave sig­nal.”

The ques­tions raised by Dr Kir­iushcheva and her col­leagues are all good ones, he says, and “some con­tin­ued scep­ti­cism is fine. But we have pre­sented ev­ery­thing we know about this event and we hope to be able to re­port on ad­di­tional events in the fu­ture”. Watch that space. In the mean­time, re­gard­less of where he stood on the is­sue of grav­i­ta­tional waves, were he still alive to­day, “con­tin­ued scep­ti­cism” is some­thing Ein­stein would doubt­less have ap­proved of.

Af­ter all, as he once said: “The im­por­tant thing is to not stop ques­tion­ing. Cu­rios­ity has its own rea­son for ex­ist­ing.”

David Ry­der /Bloomberg

Main, a sim­u­la­tion of two black holes col­lid­ing, a process that is thought to cause grav­i­ta­tional

waves. Cour­tesy the SXS (Sim­u­lat­ing eX­treme

Space­times) pro­ject; Below, top, a Ligo tech­ni­cian in­stalls a de­vice to con­trol stray light in­side one of the vac­uum cham­bers.

Cour­tesy LIGO; Bot­tom, one of two vac­uum cham­bers mea­sur­ing four kilo­me­tres in length at the Laser In­ter­fer­om­e­ter Grav­i­ta­tional-Wave

Ob­ser­va­tory (Ligo) at the Han­ford Site near Rich­land, Wash­ing­ton.

Cour­tesy Cal­tech/MIT/LIGO Lab

Th­ese plots show the sig­nals of grav­i­ta­tional waves de­tected by the twin Ligo ob­ser­va­to­ries at Liv­ingston, Louisiana, and Han­ford, Wash­ing­ton, on Fe­bru­ary 11. The fi­nal plot com­pares the data, and their sim­i­lar­ity con­firms that both wit­nessed the same event.

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