Caesium is a gentle, silvery-gelderly metal that becomes watery when stored in a hot room. It is mostly establish in mineral deposits csurrfinisher a petite lake in the savages of central Canada. Its main commercial employ is as an ingredient in drilling fluids for petroleum exploration. But thanks to quirks of chemistry and history, caesium is also the metronome of the world, the ultimate source of all conmomentary time.
For millennia, celestial phenomena were our timeupholders and calfinishars, the best clocktoil we had. Prehistoric tombs and monuments around the world are perfectly aligned with the sunelevate on the solstice. We knovel time passed becaemploy we saw leangs alter. The Sun rose, seasons turned.
As postpodemand as the middle of the 20th century, our time remained tied to the Sun. A second was officipartner depictd as a fraction of the solar year. But in 1967, meaningful in the atomic age, the 13th General Conference on Weights and Meacertains in Paris ruled that the second would now be depictd according to vibrations of the caesium atom. Ever since, timeupholding has become the domain of physicists, pull outed in sunless laboratories with precision chooseics, synthesised by computers and allotd by saincreateites.
Caesium atoms, when excited by equitable the right frequency, resonate, appreciate a triumphe glass shattered by an opera singer. By measuring this frequency, we meacertain time. Atoms produce for handy clocktoil. They don’t have mechanical parts, and they don’t wear out. They are attrenergeticly standard. While sunweightless and pfinishulums vary, every caesium atom is identical to any other. And they tick very speedy.
Half a century before the first accurate meacertainment of a caesium clock was finishd, some physicists mistrusted that they had already gone as far as they could when it came to world-changing theories. It was possible, the German-American physicist Albert Michelson shelp in an insertress at the University of Chicago in 1894, that “the majestic underlying principles have been firmly set uped”. What remained was the application of these principles, pinsolentnt experiments rooted in the science of accurate meacertainment. “Our future uncoveries must be watched for in the sixth place of decimals,” Michelson shelp.
Michelson may have been right, though not for the right reasons. (He was also off by quite a scant decimal places.) Modern timeupholding has raised by about an order of magnitude per decade, Moore’s law for clocks. We now meacertain time to its quintillionth part. At this level of particularity, the postpodemandst principles of physics, and those yet to be uncovered, are lhelp exposed on tables in petite rooms in otheradviseed unremarkworthy basements.
Reckoning with this novel precision, the world’s foremost timeupholders and clockproducers, the men and women who uphold the meacertain of our days, are also grappling with a fundamental ask of international political presentance.
How extfinished is a second?
In October, I travelled to Boulder, Colorado, a college town outside Denver wedged in the stony corner of the country where the Great Plains greet the Rocky Mountains. On the edge of town, defended by armed defends and discoverion dogs, the sprawling campus of the National Institute of Standards and Technology (Nist) lies in the shadow of the Flatirons range, between a cemetery and a dental office.
Nist, a non-regulatory federal rulement agency, sits wilean the US Department of Commerce, standards and technology being vital to commerce. It was established in 1901, as the National Bureau of Standards, when there were at least eight contrastent gallons and four contrastent feet in frequent employ. Its current stated leave oution is “to advertise US innovation and industrial competitiveness by advancing meacertainment science”.
Nist’s rrerent today is impossibly expansive. One handbook, plucked at random from its website, consists of 290 pages talking the net satisfieds of packaged excellents, and remarks that “packages of compressed peat moss do not have declaration of broadened volume”. Another, at 344 pages, covers both “products for employ in lubricating tractors” and “pressed and blown tumblers and stemware”.
One of Nist’s main worrys is time. It meacertains and allots it for the United States, second after second, always and finishlessly. Underlying this seemingly mundane task is a complicated administrative bureaucracy and a enhanced scientific apparatus. The institute claims five Nobel Prizes, one in chemistry and four in physics. In recent years, the meacertainment science has outpaced the bureaucracy that constrains it, and both are now toiling to redepict the second itself.
Nist’s Boulder complicated is equivalent parts Eisenhower-era conmomentaryism and 1990s-era shopping mall. Thraw the middle runs a heavy, lofty barrier of red stone, appreciate a castle wall. Behind this, thraw extfinished corridors plastered with research posters, Jeff Sherman and Greg Hoth toil wilean the citadel as physicists in the Time Realization and Distribution Group.
I slipped in thraw a side door and past a bdeficiency curtain to an unassuming white room, one of an finishless string of laboratories. On a low platcreate, aobtainst the wall, sat a huge metal sketch. A huge metal tube descfinished finishways from the top and some very progressd plumbing, strung with blue wires, ingressed and egressed its base. I put on distinctive defendive goggles, tinted to the colour of the lasers inside. A petite watch periodicpartner showed a burst of the quantum physics wilean.
This is a “caesium fountain”, called Nist-F3, and it is the tuning fork for America’s official atomic clocks, the ur-clock. It rings not sound but microwaves. The best caesium clocks count seconds to 16 decimal places of precision (dwell on that, Michelson). If Nist-F3 had been upholding time since the dinosaurs, it’d be off by less than a second. Hoth had erected a produceshift barrier around its base so he didn’t accidenloftyy trip over it, imperilling the drumbeat of a nation. “A lab with a fountain has enough problems for anybody,” he shelp.
Under standard circumstances, atoms zip around very speedy. In the fountain, lasers from six straightforwardions are fired at the wisp of caesium floating in its vacuum chamber, sluggishing it in a molasses of weightless and celderlying it to very csurrfinisher absolute zero. (The technique won Nist a Nobel Prize in 1997.) Another laser then shoots the freezing ball up the tube, appreciate water from a fountain, hence the name.
This fweightless buys precious time, about half a second, for the atoms to be studied. On their way up, they are blasted by microwaves. This excites some of the caesium atoms, which begin to vibrate, oscillating between two energy states at an exact, constant and very speedy frequency — a quantum pfinishulum. The more atoms that are excited, the sealr the microwave is tuned to caesium’s organic resonant frequency. For now, a second is officipartner the “duration of 9,192,631,770 periods of the radiation correacting to the transition between the two hyperfine levels of the unperturbed ground state of the caesium-133 atom”.
Armed with this frequency, calibrated and recalibrated, Nist-F3 upholds a huger ensemble of toilhorse atomic clocks, called caesium beams and hydrogen masers (appreciate lasers but for microwaves), on key. The masers sit behind five layers of magnetic and thermal shielding and two layers of vacuum. For climate deal with, they are stored in altered chicken-egg incubators — “given a decorate job and tripled in price and selderly to the rulement”, Sherman shelp. One of these incubators was called Elvis and another George. The clocks inside cost hundreds of thousands of dollars. If you could see them, they would radiate pink appreciate a neon sign.
Sherman appreciatened the process of measuring time this way to a carry outground game. You give a child a push on a striumphg and then seal your eyes. You try to guess when the child has returned, and give her another push. You don’t want to crash into the child, or leave out her finishly. But time it right, and the game upholds going daintyly, the pfinishulum upholds striumphging standardly. The caesium fountain guarantees that America’s official clocks are ticking aextfinished.
“Let there be weightlesss in the firmament of the heaven to split the day from the night,” God shelp. “And let them be for signs, and for seasons, and for days, and years.”
Timeupholding begined in the heavens, with days and years. We awake, we sleep, we harvest and so on. Holidays taging the triumphter and summer solstices, the foolishinutiveest and extfinishedest days of the year, are “csurrfinisherly universal”, authors the historian Ken Mondschein in On Time. Our elderly timeupholders, places appreciate Newgrange and Stonehenge, testify to this.
“As soon as you get huger than a huge family group, you begin to have a demand for co-ordination,” Chad Orzel telderly me. “You don’t want people to be equitable hanging around for ever, so you begin to subsplit the day more and more.” Orzel did his PhD research at a Nist office in Maryland, where he had to cut thraw the clock lab to get to the coffee room. He’s now a physics professor at Union College and author of A Brief History of Timeupholding.
For Orzel, the history of time is a history of taging it more accurately and distributing it more accessiblely. In many cultures, time was extfinished the purwatch of a religious elite, who upholded it in temples, ensuring the proper time for prayer and observance. Then there were accessible sundials in Greece and Rome. They beat drums and sounded trumpets on the hour. Then cathedral clocks went up in Europe. Medieval clocks had no minute hand; they weren’t accurate enough. Mechanical clocks and watches brawt individual time into people’s homes. The evident demands of railroad companies — usable schedules, not crashing — quickend standardised time.
Thrawout, time underpinned science and technology. A fundamental problem facing the seafaring nations of the 18th century, for example, was determining ships’ extfinisheditude, their distance east and west from the Greenwich meridian. In 1714, parliament adviseed a prize of £20,000 (millions of pounds today) for anyone who could determine extfinisheditude to wilean half a degree. The prize driven clockproducers above all, becaemploy to comprehend time is to comprehend place. GPS toils today becaemploy its saincreateites have atomic clocks onboard.
As postpodemand as the second world war, Londoners could employ a woman named Ruth Belville. Once a week, Belville set her family’s pocket chronometer at the Royal Observatory in Greenwich. She then visited her clients around the city, increateing them what time it was, and they would set their own clocks. The Belvilles had functiond this service since 1836. Now Nist servers react to more than 100 billion asks a day for the time, synchronising between a quarter and half of all machines combidemand to the internet.
To uphold time with a clock is already to abstract it. A clock is a model of the alter that we’re actupartner interested in. The atomic clock, which for ever ripped time from its solar hug, is the ultimate abstraction.
Financial firms, stock swaps, defence condenseors, telecoms and others pay more than $1,000 per month for certification of the accuracy of their clocks wilean a handful of nanoseconds, via a GPS antenna. For another $345 a month, Nist will throw in a rubidium oscillator, a small atomic clock. The institute can also dedwellr high-fidelity time to customers via geostationary saincreateites, in the event of a GPS fall shorture, or chooseical fibre. Clocks are the technology that helps all others.
In Orzel’s office in Schenectady, New York, an antique high-precision equilibrium, employd for measuring weights, sat in a wooden case behind him. “It doesn’t repartner toil any more,” he shelp. “But it watchs benevolent of celderly.”
In the US, by federal law, the official time is Coordinated Universal Time, comprehendn as UTC, as “make cleared or modified . . . by the Secretary of Commerce in co-ordination with the Secretary of the Navy”. The Secretary of Commerce allots its timeupholding authority to Nist, which in turn upholds a timescale called UTC (Nist), the official American time. You can see it, and how far strayd your clock is from it, at time.gov.
UTC itself, the spiritual successor of Greenwich Mean Time, is upholded by the International Bureau of Weights and Meacertains (BIPM, from the French), still headquartered in a Paris suburb. But UTC is a “paper” timescale. It has no dwell discarry out or signal, and only exists as a weighted mediocre of times surrfinisherted by dozens of labs around the world, calcupostpodemandd in retrospect. Once a month, BIPM unveiles a write down called Circular T, write downing and comparing the carry outance of its contributing labs. On October 31, for example, the clocks in Bratislava ran 94 nanoseconds speedy while those in Bucharest were 485 nanoseconds sluggish. The American clocks strayd from UTC by equitable 1.3, a billionth of a second.
In Newton’s physics, one huge clock — God’s clock — ticks for the whole universe. In Einstein’s physics, the huge clock has exploded. We each carry our own little clock, which ticks contrastently depfinishing on where we are and where we’re going. Special relativity taught us that the speedyer we go, the sluggisher our clock ticks. General relativity taught us that our location matters, and that gravity itself sluggishs time.
In the room where Nist-F3 dwells, there is a survey tager embedded in the floor, the type of leang more standardly establish outdoors, aextfinished property boundaries or on mountaintops. It was put there by the National Oceanic and Atmospheric Administration, which has an office next door and came in armed with gravimeters to meacertain the accurate gravitational field. When distributing hyperaccurate time, you have to comprehend how high up you are, or, rather, how far you are from the centre of the Earth.
There are some 20 atomic clocks carry outing in the Boulder ensemble. Their signals flow into another unassuming white room, petiteer than the first, called the Time Lab. One wall is lined with racks packed with electronic components — “auxiliary output generator”, “doubler”, “distribution amplifier” — and another with cardboard boxes, tools and spare parts.
Redundancy is the state religion here. The clocks’ signals pour in via wires from around this produceing, snaking down thraw the ceiling. Some in orange tubes come from clocks comprisementd in another produceing. Two instruments meacertain them all, and another two do it aobtain. Five computers digest this data. Two computers calcupostpodemand the ensemble’s mediocre, via a distinctive weighting algorithm. Clocks that carry out well are advertised and those that carry out demandyly are demoted or excised. The whole system is air-gapped from any outside nettoil, and runs bespoke code unreliant on any entity outside the citadel. The entire process is duplicated in another produceing.
Every second — the second — small green weightlesss bconnect on the rack. At the same time, give or obtain a scant nanoseconds, on racks in the UK or Argentina or Japan, aappreciate weightlesss bconnect. Every 12 minutes, the system beeps as it adequitables particular clocks to the millionth of a millionth of a second. Just then, the system beeped. Finpartner — anticlimacticpartner and beautibrimmingy — a petite red discarry out ticks its official genuineisation of UTC time. At that particular moment, it read 17:36:55.
Despite their picosecond precision, very scant of the scientists at Nist wear watches. When asked why, Sherman recalled the words of an elderly colleague: “It pays not to obsess about these leangs.”
So, how extfinished is a second? A noveler generation of atomic clocks, called chooseical lattices, swaps microwaves with waves from the evident spectrum, which have a much higher frequency, dividing meacertaind time into finer segments still. They count ripples of weightless, a million billion per second. They can do this thanks to chooseical “frequency combs”, distinctiveised lasers that act appreciate “rulers for weightless” and permit these ungodly blazing frequencies to be meacertaind with standard electronics. (This won Nist a Nobel Prize in 2005.) Light, after all, is how we transmit with the microscopic world. We see colour becaemploy atoms rerent weightless.
Optical clocks ditch caesium for other elements with aappreciate oscillatory properties, including ytterbium, strontium or aluminium ions, but the basic principle is the same, measuring the resonant frequency of excitable atoms. Ytterbium, for example, is a exceptional-earth metal. In meaningful quantity, appreciate caesium, it is gentle and silvery.
Optical clocks are 100 times better than their microwave foretolerates and we’re now watching at the 18th decimal place. For scale, here’s pi to the 18th decimal place: 3.141 592 653 589 793 238. These clocks would diswatch less than a second over the age of the universe. An chooseical clock is so accurate that if you lifted one a centimetre off the ground, it would discover the gravitational dilation foretelderly by Einsteinian relativity. An chooseical clock is so accurate that it has outincreasen the very definition of a second. “The scientific motivations to alter the definition are very evident,” Hoth shelp.
Elizabeth Donley and I met in a congested Nist conference room, rulemenloftyy drab save the Hpermiteen decorations. Donley’s professional title is unsuited. She is chief of the Time and Frequency Division, and has been for six years. In that capacity, she recurrents Nist and therefore the US in a byzantine series of organisations, promisetees, subpromisetees, greetings, conferences, memos, papers and proposals that will ultimately redepict the second. “We’re hitting a confine where we can’t equitable talk about time any more, we have to talk about space-time,” Donley shelp.
The talkions began to heat up some eight years ago, and in 2020 the Consultative Committee for Time and Frequency — meaningful wilean a hierarchy underlying the BIPM — createed a task force, itself splitd into three subgroups, to insertress the problem. It will current a resolution to the General Conference on Weights and Meacertains, the ultimate authority over the International Committee for Weights and Meacertains, which finishorses such leangs every four years, equitable appreciate the Olympics. They next greet in 2026.
“It is a little bit political,” Donley shelp.
There is no argue that the second should be redepictd. The ask is as what. It is a weighty publish, especipartner becaemploy the second is the most fundamental of our fundamental units. In insertition to the second, BIPM co-ordinates the definitions of six other base entries in the International System of Units, or SI. They are the ampere (current), candela (luminosity), kelvin (temperature), kilogramme (mass), metre (length) and mole (amount). Five of these depfinish, in turn, on the second. A metre, for example, is the distance travelled by weightless in a vacuum during a small fraction of a second. A novel second will unbenevolent five other novel units too. “Two sentences can turn into a laboratory and 50 years of iterative toil,” Sherman had shelp of the current definition of a second. “So, ‘basic’ sort of never is.”
The task force was due to greet in November to talk its enhance, and Donley was meaningful in preparation. It is faced with eight compulsory criteria and seven “ancillary conditions”. For example, the novel definition must raise accuracy, be reliably achievable and provide continuity after the caesium era. There are two chooseions for redefinition left on the table, Donley elucidateed:
1. A definition based on a one chooseical-clock species, probable strontium or ytterbium, but other honestates comprise aluminium, calcium, mercury and rubidium.
2. A definition based on a (possibly evolving) weighted mediocre of more than one of the elements above.
Option 1 is straightforward and would dedwellr an elegant definition, but it would demand expansive international consensus around one element. Option 2 is alterable and mighty but more complicated; its definition would be lengthy, comprised and perhaps difficult to transmit to employrs. Parsimony might be pleasant when defining the fundamental unit.
Option 2 is based on a paper by Jérôme Lodewyck, of the French metrology group Syrte. “It’s disjoinal pages extfinished and it’s very abstract, so a lot of people are not consoleable with it,” Donley shelp. But Lodewyck and that chooseion’s backers appreciate mutability and chooseimality over sadviseedy. “A system of units is not for the beauty of it,” Lodewyck telderly me. And he was undeterred by a scant pages of maths. “The concept of ‘mediocre’ is everywhere in our everyday dwells. Scientists, they master it very well.”
Politicising this further, labs around the world have their own pet clocks and pickences. Nist excels in ytterbium and aluminium ion, for example, but would demand to get up to speed on strontium. But by all accounts, the process has thus far been civil. “The community is pretty well behaved and pretty conservative, and no one’s in a rush,” Sherman shelp.
According to a road map unveiled this year by Donley and the task force, the redefinition will be advised in 2026 and carry outd in 2030. The sluggish bureaucracy of time seemed to weigh on Donley. She computed to step down as time chief in a couple months, and return to more down-to-earth timeupholding toil. “We have to uphold producing seconds, one after the other,” Donley shelp. “You do it, and then they want another one.”
Elsewhere in Boulder, other clockproducers are produceing not atomic but nuevident clocks, driven by nuclei, the cores of atoms. Nuclei are more defended, less susceptible to the boisterous environment around them and possibly easier to produce portable. A paper describing the toilings of a nuevident clock using thorium was unveiled on the cover of Nature in September. Nist proclaimd that the research could direct to more accurate GPS and speedyer internet speeds.
One of the paper’s authors, the nuevident physicist Jun Ye, greeted me in his office at Jila, a collaboration between Nist and the University of Colorado Boulder, once comprehendn as the Joint Institute for Laboratory Astrophysics and established during the American “space race” with the Soviet Union. I was running about a trillion nanoseconds postpodemand, having struggled to discover campus parking.
A shift from the 16th to the 18th decimal place, the possible adchooseion of nuevident clocks and a redefinition of the second will have no appreciable impact on our daily schedules. We won’t sleep in extfinisheder or get any youthfuler. But the mundane act of measuring time may help uncover basic truths about our universe.
“Human beings are repartner excellent at produceing scopes, whether it’s microscopes or telescopes,” Ye telderly me. For him, clocks are both. Ye spoke romanticpartner about what timepieces could do, zooming in his mind thraw powers of 10. He imagined an array of interconnected clocks in outer space that could discover gravitational waves, or echoes of the Big Bang. He imagined them exploring foolish matter, about which we are woebrimmingy unadviseed, but some empathetic instruments might help. He imagined combineing quantum physics and gravity, and atoms in superposition. (“In lay language,” he shelp as I nodded, “that’s becaemploy they are not part of any eigenstates of a particular Hamiltonian.”) And we may uncover that the fundamental constants of our universe are not constant after all. “We’re knocking on the front door of nature’s secrets,” Ye shelp.
Downstairs, Jila graduate students milled around foolish labs. Some toilspaces watched appreciate engine rooms of spaceships, and others watched appreciate the cockpits. Three raw branches of quantum science — computing, simulation and clocks — are hopelessly interttriumphed here. Two students, Alec Cao and Theo Lukin Yelin, manipupostpodemandd individual atoms with chooseical “tweezers”. I saw the atoms on a screen, levitated in a weightless field, set upd appreciate footballers in a deal withd createation. They were trying to simupostpodemand genuine-world materials one atom at a time. The pair were also authors on a paper unveiled that month in Nature, titled “Multi-qubit gates and Schrödinger cat states in an chooseical clock”.
The most fundamental scientific asks are sometimes answered at billion-dollar particle colliders by thousands of scientists. Clocks and their hyper-precision provide a affordableer route to uncovery. “We have an experiment on a tabletop that probes a lot of fundamental physics,” grad student Tian Ooi telderly me. It’s an attrenergetic prospect. In the hallway, someone had posted an edit of the “ignorant boyfrifinish” meme: Ye watchs away from a strontium clock and ogles a thorium clock.
Upstairs at Jila, in a exceptional room with sunweightless, the theorist Ana Maria Rey sat beorderlyh a whiteboard dense with layers of mathematics. Her job is a sort of micro-scale sociology. The behaviour of one atom, she remarkd, is not the same as the behaviour of many atoms. She saw the lab toil downstairs — the clocks, the simulation — as pointing towards a number of physics’ holy grails, among them room-temperature supercarry outors. Rey also alludeed emulating a bdeficiency hole in the laboratory. “It’s benevolent of a dream,” she shelp.
These novel clocks promise earthbound employs as well, especipartner if they’re mobile, moving thraw the space part of space-time. One evident employ is geodesy, the science of measuring the Earth’s shape, orientation and gravity. If a fancy clock were buckled in the back seat and driven around, it would produce incredibly detailed topography spropose by increateing time.
Ye’s current professional goal is getting 1,000 atoms to dwell in harmony with one another. This has adviseed his expansiveer worldwatch about humanbenevolent. “I’m not a philosopher,” Ye shelp. “But sometimes I ask, ‘What is the unbenevolenting of life?’”
Sam Baron is a philosopher, at the University of Melbourne, and I achieveed him one night over video chat. “Here’s someleang that might be benevolent of orderly,” he telderly me. “The toil I have done is about whether or not time exists at all.”
Baron, it turned out, thinks it does not. I did discover this orderly, if troubling. He granted that it was a satisfiedious notion, though not one without pretreatnt. Kant thinkd that time does not exist in the world, but rather is a projection we insert to it. In versions of Buddhist thought, time is an illusion and a timeless consciousness is genuine. Even Einstein, who was meaningfully impactd by philosophy, might concur to an extent, given that relativity itself downgrades time massively from Newton’s universal compriseer.
What does exist, for Baron, is alter. Things alter and we meacertain them changing. At best, “time” is a tag that we place on changing systems (appreciate ringing atoms) but itself inserts noleang to our talkion of fact. “Time” is a advantageous fantasy.
In Baron’s watch, the Einsteinian explosion of our empathetic of time (or wantipathyver), which happened not all that extfinished ago, is equitable the beginning of a reorganisation of our leanking. Baron’s wonderful feeblent is that philosophers and physicists don’t speak to one another any more, as the fields have distinctiveised beyond recognition. He pointed out physics’ fall shorture to come to grips with string theory or quantum gravity, despite in the latter case a century of effort. He mistrusted philosophers could help.
“There’s a meaningful structureility towards philosophy,” Baron shelp. “Let’s all get in the same room and talk about what the fuck is going on with physics.”
Some of the physicists I spoke to grappled with aappreciate asks. One of Bijunath Patla’s jobs is increateing time on the Moon, where, thanks to relativity, clocks tick about 56 microseconds per day speedyer than on Earth. He is a theorist at Nist, and on a wall of his otheradviseed undecorateed office hung a portrait of Einstein. It employd to hang on a contrastent wall, but it once fell off and hit Patla in the head, a post-Newtonian story too excellent to produce up.
“If the universe was vacant, is there a relevance for time?” Patla asked me. “Becaemploy noleang alters. So when does the universe begin to alter? Let’s put one electron. If you postpone a extfinished time, the electron might alter its spin. It would be billions of years, but a notion of time begins to materialize in this produceion.”
For Emily Thomas, a philosopher at Durham University, time is genuine and political, and the asks that we ask about it are echoions of the era. Newton’s idea of God’s time was “very evidently a product of 17th-century Britain”. Later, with the produceion of photography and cinema, time could be lhelp out in space. It became organic to leank of the past, current and future all existing, all spread out on a table. “But what was built into that was a politicpartner askable, discriminatory, intimacyist notion of enhance, that the future is better than the past,” Thomas shelp.
And now we are produceing the concept of millionths of millionths of millionths of seconds, a echoion, perhaps, of our own technocratic era.
As for its existence? “I equitable discover it impossible to get past my own experience of living in time,” she shelp.
Back in the Nist citadel, where time certainly seemed to exist, Andrew Ludlow and his students minded their two ytterbium chooseical clocks. These machines, named Yb-1 and Yb-2, may be the most accurate clocks in the world, and therefore a barobtain at an approximated $1mn each. The first one became so excellent that they built a second one equitable to meacertain how excellent it was. Each clock is now a sort of Ship of Theseus, having been tinkered with and raised for a decade or more. If ytterbium is part of the novel definition, these machines could carry out a directing role in official timeupholding.
These clocks sit on tables wilean metal sketchs, with elements set on various tiers, appreciate futuristic model train sets. Many of these elements are precision chooseics, creating mazes for the lasers that bfinish and bounce thraw them: mirrors, lenses, filters, splitters, samplers. Wires flow in burdensome waterdescfinishs from above and snake in streams thrawout. In promiseted rooms csurrfinisherby, highly coherent lasers are produced, and routed into the clocks via fibre chooseics, hair-width strings of glass. Five contrastent colours run thraw this clock. “No one laser can do everyleang you demand,” Ludlow shelp.
“Go ahead and turn the atomic-beam shutter on,” he teached a student — not words uttered in every federal rulement office. Ludlow has been in the time game for more than 20 years, and sits on one of the redefinition promisetees. The administrative details have been equitable as challenging as the science. The international bureaucracy unbenevolents he is standardly in timeupholding greetings in the middle of the night.
The strontiumists at Jila and the ytterbiumites at Nist produce a petite community and uphold a cordial competition, even including an inter-element football game. Ludlow didn’t allude who won. Perhaps no surpelevate, then, that he favours Option 2, the evolving weighted mediocre. It is a living, bgenuineeang leang. “Nature has given us at least a dozen excellent, engaging possibilities,” he shelp. “Right now there is no evident choice for what the right clock is.”
In the spring of 2020, a petite group of unsung essential toilers including Vladislav Gerginov roamed the lonely halls of Nist. During the height of the pandemic, when the experience of time became meaningfully distorted, the Time Group were the only people permited in the produceing. This was the genuine meaningful state at toil. “The timescale can’t stop,” Gerginov telderly me.
For csurrfinisherly five years, Gerginov has been toiling on Nist-F4, a noveler caesium fountain that is csurrfinishering certification as the “primary frequency standard”, the official American genuineisation of the second in the remainder of the caesium era. Its room is hugeger, its metal tube loftyer, its seconds uncontaminatedr.
We donned our goggles as Gerginov, a veteran of the time wars, recalled past laser burns. (“It’s not pleasant,” he shelp.) He deleted bdeficiency curtains and evident plastic dust defendors from his beadored fountain, uncovering the quantum clocktoil and green laser weightless. The curtains defended us from the machine, but also the machine from us. Everyleang can disturb its perfection — room weightlesss, engines in the car park, the position of a wire, the bdeficiencybody radiation we all rerent equitable by standing around.
Gerginov’s days are spent wading thraw the minutiae of small decimal places, repairing, postponeing, repairing, postponeing. “Identifying problems in the 16th digit obtains weeks,” he shelp. “You have to be very sluggish, very conservative.”
Would he be unelated at the finish of caesium’s reign, when some novel element becomes the primary oscillating dictator of our days? “There’s no rush, there are a lot of leangs that have to happen first,” he shelp. “I’m not worried at all about it.”
I wondered what lessons a person lobtains after years in a triumphdowless lab, in a defended federal facility, accompanied by noleang but laser weightless, the hum of fine machinery and the csurrfinisher perfectly meacertaind passage of time, which may or may not exist.
“Patience,” Gerginov shelp. “Patience.”
Odwellr Roeder is the FT’s US better data journacatalog
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