2019-09-02 Bloomberg Businessweek

69

Tm

Thulium

60

 Thulium $12,000 / kg 99.95% pure sample on Amazon.com

 Ytterbium $15.50 / kg 99.99% ytterbium oxide, China market

 Lutetium $609/ kg 99.9%lutetium oxide, Chinamarket

T

hemostimportantpartofone

ofthemostpreciseclocksinthe

worldis a paper-thin,staple-size

pieceoflutetium.It restsinsidea sound-

proof,vibration-proof,mini-fridge-size

box,whichsitsatopa $22,000motion-

dampeningtable.MurrayBarrett,asso-

ciateprofessorofphysicsattheNational

University ofSingapore, reaches for

the case toshow me. “Itshould be

OK,”hesaysinhiswarmNewZealand

accent.Butthenhehesitates.We’rein

a darkenedlaboratoryfilledwithlasers

whosebeamsbank,split,andintensify

througharraysofcrystalsandelectron-

ics.“Normallyit’sOK,”hesays,backing

awayfromhisstill-very-much-a-work-in-

progressclock.“ButI’mnotsureif we’re

runninganythingornot.”

Barrett’sclock,locatedattheuniver-

sity’sCentreforQuantumTechnologies,

is intendedtoslicetimeintomoreand

smallersegmentsthananyclockbefore

it.Ananalogstopwatchcantypically

70

Yb

Ytterbium

71

Lu

Lutetium

By Adam Minter Thefutureoftimekeepingmaybebuiltonlutetium

The

Infinitely

Split Second

divide the second into 10 pieces: 0.1 sec-

ond, 0.2 second, etc. The lutetium clock

will, in theory, add 14 zeros to the right

of that decimal point, thereby segment-

ing the second into (roughly) a qua-

drillionpieces,andremainaccurateto

withina secondif leftrunningcontinu-

ouslyfor30 billionyears.Eventhesmall-

estvibrationsfrom,say,theexhaust

fansthatkeepthelaboratoryenviron-

mentcleanareenoughtoupsetthat

precision—andwithit,allthelab’swork.

Sofar,thepotentialapplicationsfor

a clockwith 15 decimalplacesofpre-

cisionaretheoreticalandaspirational.

Butthat’snotstoppinglabsaroundthe

world fromcompeting,usingdiffer-

entelements,toreachthesamegoal.

Lutetiumis insomewaystheleastlikely

elementtofeatureina winningeffort.

Notonlyisit relativelyrareinnature;

becauseofitshighcostandsimilarityto

otherelements,itsknownapplications

are alsorare. Thusresearchersand

industrytendtopassit over.If Barrett

andhislabsucceed,theglobalmar-

ketforlutetiumwon’texpandsignifi-

cantly—afterall,theclockuseshardly

any.Nevertheless,lutetiumwillquickly

becomethebeatingheartofscience

andtheglobaleconomy.

A

ll clocksmeasuretimebyfollow-

inga recurrentevent.Thatcan

meantrackingtherotationof

theEarthviatheshadowsona sundial,

orit canmeancountingtheswingsofa

pendulum.Noneofthesetimekeeping

methodscanproducea measurement

that’sconstantinalltimesandplaces,

though.Temperatureandhumidityalter

mechanicalclockparts,lengtheningor

shorteningseconds.Timekeepingbased

on astronomicalobservationisham-

peredbytheirregularityoftheEarth’s

orbitaroundthesun.

Thebulkofhumanhistorysofar

hasn’trequiredmuchprecision,sothe

limitationsofclockswereneverreally

a problem.Theninthe19th century,

atomicphysicsopenedupthepossibil-

ityofa universal,unchangingdefinition

oftime.Theideawasdeceptivelysim-

ple.Eachatomofanelementonthe

periodictablevibratesuniquelywhen

bombardedbyanexactfrequencyof

(MOSTLY)

USELESS

BySamanthSubramanian

 WHAT’S IT LOOK LIKE?

It’s silvery and shining if

preserved in an ampoule of

an inert gas such as argon.

 WHY’S IT (MOSTLY)

USELESS?

Thulium occurs at 0.5 parts

per million in the Earth’s

crust, and it’s difficult and

expensive to extract.

 WHAT’S IT USED FOR?

Arc lights use thulium to

provide soft green light.

Euro banknotes contain

traces of thulium and other

elements that fluoresce

under ultraviolet light,

for security. Max Whitby,

founder of Red Green &

Blue Co. in London, which

sells periodic tables that

hold element samples,

says he once heard of

toothpaste containing thu-

lium, but he hasn’t been

able to track down the

brand.

 CAN I GET SOME?

Why yes. A 99.95%-pure

gram sample costs $12 on

Amazon. A Sunmaster Full

Nova 315-watt lamp, which

includes not just thulium

but dysprosium in its arc

element, costs $109.85.

A €10 banknote costs €10.

THULIUM: SPL/SCIENCE SOURCE. LUTETIUM: PHOTOGRAPH BY ORE HUIYING FOR BLOOMBERG BUSINESSWEEK.