Bloomberg Businessweek USA - 02.09.2019

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, China market

T

he most important part of one

of the most precise clocks in the

world is a paper-thin, staple-size

piece of lutetium. It rests inside a sound-

proof, vibration-proof, mini-fridge-size

box, which sits atop a $22,000 motion-

dampening table. Murray Barrett, asso-

ciate professor of physics at the National

University of Singapore, reaches for

the case to show me. “It should be

OK,” he says in his warm New Zealand

accent. But then he hesitates. We’re in

a darkened laboratory filled with lasers

whose beams bank, split, and intensify

through arrays of crystals and electron-

ics. “Normally it’s OK,” he says, backing

away from his still-very-much-a-work-in-

progress clock. “But I’m not sure if we’re

running anything or not.”

Barrett’s clock, located at the univer-

sity’s Centre for Quantum Technologies,

is intended to slice time into more and

smaller segments than any clock before

it. An analog stopwatch can typically

70

Yb

Ytterbium

71

Lu

Lutetium

By Adam Minter The future of timekeeping may be built on lutetium

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-

drillion pieces, and remain accurate to

within a second if left running continu-

ously for 30 billion years. Even the small-

est vibrations from, say, the exhaust

fans that keep the laboratory environ-

ment clean are enough to upset that

precision—and with it, all the lab’s work.

So far, the potential applications for

a clock with 15 decimal places of pre-

cision are theoretical and aspirational.

But that’s not stopping labs around the

world from competing, using differ-

ent elements, to reach the same goal.

Lutetium is in some ways the least likely

element to feature in a winning effort.

Not only is it relatively rare in nature;

because of its high cost and similarity to

other elements, its known applications

are also rare. Thus researchers and

industry tend to pass it over. If Barrett

and his lab succeed, the global mar-

ket for lutetium won’t expand signifi-

cantly—after all, the clock uses hardly

any. Nevertheless, lutetium will quickly

become the beating heart of science

and the global economy.

A

ll clocks measure time by follow-

ing a recurrent event. That can

mean tracking the rotation of

the Earth via the shadows on a sundial,

or it can mean counting the swings of a

pendulum. None of these timekeeping

methods can produce a measurement

that’s constant in all times and places,

though. Temperature and humidity alter

mechanical clock parts, lengthening or

shortening seconds. Timekeeping based

on astronomical observation is ham-

pered by the irregularity of the Earth’s

orbit around the sun.

The bulk of human history so far

hasn’t required much precision, so the

limitations of clocks were never really

a problem. Then in the 19th century,

atomic physics opened up the possibil-

ity of a universal, unchanging definition

of time. The idea was deceptively sim-

ple. Each atom of an element on the

periodic table vibrates uniquely when

bombarded by an exact frequency of

(MOSTLY)

USELESS

By Samanth Subramanian

 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.