The Economist - USA (2021-02-13)

80 Books & arts The Economist February 13th 2021

on which scientists build their hypothes-

es. Those hypotheses are then ritually torn

apart by other scientists and—if they can

withstand sustained critiques and are not

contradicted by further evidence from the

real world—they might lay claim to being

true. In science, changing your mind in the

light of fresh information is seen as a good

thing. If a new conjecture gathers support-

ing evidence and eventually supplants

years of previous thinking on a topic, sci-

entists are duty-bound to abandon the de-

funct ideas and embrace the new ones. The

more radically an idea diverges from the

mainstream, however, the greater the scru-

tiny it will inevitably face. Carl Sagan, an

American astronomer, once summed this

up: “Extraordinary claims require extraor-

dinary evidence.”

That is the theory, at least. But like any

profession, the path of scientific research

can be influenced (both positively and

negatively) by fashions and personalities,

which can also determine who receives

funding and which ideas get heard. Take

the search for extraterrestrial intelligence,

commonly known as seti. Since the 1960s

astronomers have been listening to the

skies for any signs of radio signals sent out

by technologically capable life beyond

Earth. For most of its existence, though,

setihas been marginalised, dismissed as a

lesser use of time and resources than the

more prestigious study of black holes, sub-

atomic particles, stars, galaxies and other

“real” physics. The steadfastly radio-silent

skies have not burnished seti’s image as a

discipline to be taken seriously. 

Mr Loeb says he has always found the

hostility to seti bizarre. Modern main-

stream theoretical physicists, he points

out, accept the study of spatial dimensions

beyond the three (length, breadth and

depth) with which people are familiar. Ex-

perimental evidence for these dimensions,

however, does not exist. Similarly, many

leading cosmologists think that this uni-

verse is one among an infinite number of

others that exist together in a “multiverse”.

But, again, experimental evidence for that

proposition does not exist. String theory,

the putative “theory of everything” that is

meant to bind together the physics of the

cosmos with that of subatomic particles, is

considered scientific even though there is

no direct evidence to prove it is real.

E.T. go home

Compared with these abstract theories, the

notion that there could be life elsewhere in

the universe, when it is known to exist on

Earth, should not seem so radical a subject

of study. Mr Loeb thinks resistance to it

comes from two sources. First, the “laugh-

able” popular narratives in which aliens

lay waste to Earth’s cities and possess su-

perhuman wisdom. He is no fan of science

fiction that ignores the laws of physics.

Butthemoreimportantreason,hesays,

isa conservatismwithinscience,whichis

sustainedbythedesireofindividualscien-

tiststokeeprisklowandfundinghigh:

Bylimitinginterpretationsorplacingblin-

dersonourtelescopes,weriskmissingdis-

coveries...Thescientific community’s pre-

judiceorclosed-mindedness—howeveryou

wanttodescribeit—isparticularlyperva-

siveandpowerfulwhen itcomesto the

searchforalienlife,especiallyintelligent

life.Manyresearchersrefusetoevenconsid-

erthepossibilitythata bizarreobjectorphe-

nomenonmightbeevidenceofanadvanced

civilisation.

Thefactthataccusationsofconserva-

tisminmainstreamsciencearebeinglev-

elledbyanastronomersituatedatthevery

heartofthescientificestablishmentmay

seemironic.MrLoebhas,afterall,spent

mostofhiscareeratprestigiousAmerican

institutions,includinga recentspellasthe

headoftheastronomydepartmentatHar-

vardUniversity.Heisalsochairmanofthe

boardonphysicsandastronomyoftheus

NationalAcademies.

Hisprominentstatusinastronomycir-

cleshasensuredthatMrLoeb’sradicalhy-

pothesishasattractedwidespreadatten-

tion.Allthesame,andashereportsinhis

book,it wouldbe“puttingthemattermild-

ly”tosaythathisideahasbeenmetwith

disapproval by his scientific colleagues.

WritinginNatureAstronomyinJuly2019,a

researchteamassembledbytheInterna-

tionalSpaceScience Instituteconcluded

thatithadfound“nocompellingevidence

tofavouranalienexplanationfor‘Oumua-

mua”.ItdismissedMrLoeb’stheoryasone

notbasedonfact.

Thisisnothisfirstbrushwithscientific

celebrity.In 2016 hewastheastrophysical

brain behind Breakthrough Starshot, a

$100m project fundedby Yuri Milner,a

Russiantechbillionaire,thegoalofwhich

is to dispatch a fleet of tiny probes called

Starchips to Alpha Centauri, the nearest

star to the sun. They are to be equipped

with cameras able to relay any signs of life

they might find back to Earth. Mr Loeb

worked out that it might be possible to ac-

celerate a Starchip to around 20% of the

speed of light if it were fitted with an ultra-

thin sail and a 100-gigawatt laser were di-

rected towards it for a few minutes. So

launched, the Starchips would in theory

make the 4.4-light-year journey to Alpha

Centauri in between 20 and 30 years.

The Breakthrough Starshot project was

announced a year before the discovery of

‘Oumuamua. The hunt for life elsewhere

may well have been on Mr Loeb’s mind

when he was contemplating the object’s

most intriguing anomaly: the weird way it

hadmovedpastthesun.

In June 2018 scientists reported that

‘Oumuamua’s trajectory had deviated

slightlyfromtheoneit mighthavebeenex-

pectedtofollowifithadbeendetermined

purelybythesun’sgravitationalattraction.

Asitpassedthesuntheobjectwaspushed

away by an unexplained force. Comets

sometimesbehavelikethiswhentheyget

closetothesun,butintheircasetheforce

iseasytoexplain:a tailofdustandgasis

ejectedfromtheballoficeasit isheatedby

thesun,whichgivestheobjecta rocket-

likepush.Yetnosuchtailwasdetected

near‘Oumuamua.

Sailingclosetothesun

MrLoebhadanotherhypothesis:perhaps

sunlightwasbouncingofftheobject’ssur-

facelikethewindoffa thinsail.Athin,

sturdy,lightsail,ofthesortthathehad

himself proposed for the Breakthrough

Starshotproject,wouldbetechnicallyfea-

siblefora moreadvancedcivilisation.In

anycase,sucha sailcouldnotoccurnatu-

rally;itwouldhavetobeengineeredbyin-

telligentbeings.

Hemayormaynotberightabout‘Ou-

muamua.Butthathardlyseemstomake

muchdifferencetowhatisultimatelythe

main thesisofhisbook.Conservatismmay

notbeuniquetoastrophysics,heargues,

butit is“depressingandconcerning”given

thehugenumberofanomaliesstillper-

ceivedintheuniverse.MrLoebissurely

correctthat scientistsstudyingthevast-

nessofthecosmosshouldentertainrisky

ideasmoreoften,fortheuniverseisun-

doubtedlymorewildandunexpectedthan

any extremes conjured by the human

imagination. “Extraterrestrial” considers

thepossibilityofintelligentlifeelsewhere,

butitscoremessage,anupdatetoSagan’s

maxim,isaimedsquarelyatlifeonEarth:

“Extraordinaryconservatismkeepsusex-

traordinarilyignorant.” 

Loeb’s visions

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To read a profile of Avi Loeb in 1843 magazine, go to

economist.com/1843/aliens