New Atomic Clock 1000 Times More Accurate

stevelinton writes "The UK National Physical Laboratory has a new atomic clock potentially 1000 times more accurate than current cesium clocks: to within 1 second in about 30 billion years! This could lead quite soon to a new definition of the second, and in a while to improved resolution in GPS successor systems. More interestingly, there are theories that some of the universe's fundamental dimensionless constants may have changed by a parts in a million over the last 10 billion years or so. These clocks are so accurate that they should be able to detect these changes over a year or two."

Comments

I'll alert Britannica...

[grub]

This could lead quite soon to a new definition of the second

Now all we need is a13 year old to update the wikipedia entry.

Re:I'll alert Britannica...

[bstadil]

Now all we need is a13 year old to update the wikipedia entry

Hey! Wait a secon........never mind

Yes, but...

[untaken_name]

...what if someone forgets to wind it?

Great!

[nixdorf_]

My boss will now know with 1000x the accuracy exactly how late I am. Wonderful!

Accurate distance too?

[Ckwop]

Great.. now I can measure measure how late the train is to an accuracy of a few attoseconds. hehe

The great thing about getting more accurate timing is that it should allow you to measure distances with the same accuracy. I think that by shining two different coloured lasers against a mirror and measuring the beats in the interference pattern of the returned beam it should be possible to measure a metre very exactly.

Anyone know if this is garbage or does more accurate time mean more accurate distance.

Simon.

Re:Accurate distance too?

[MasterC]

The length of the meter is defined by time

http://physics.nist.gov/cuu/Units/meter.html

"The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second."

So if you can measure time more accuractly then you can measure a meter more accurately.

Re:Accurate distance too?

[Mister Attack]

The trouble with measuring a meter this way is that it's tricky, to say the least, to know the frequency of a laser beam to high enough precision for this to be a useful measurement. You'd basically have to do exactly what these guys are doing -- cool some ions to within a few microkelvins of zero, use them as a frequency reference and lock a laser to them. Then you'd have to do it again with a different frequency. Then you'd have to actually measure the intensity of the standing wave to high enough resolution that you could get a reasonable measurement. So basically, don't hold your breath.

Much more reasonable is to keep the current definition of the meter, which is the distance that light travels in 1/299,792,458 second in a vacuum. Then your better clock gives you a more accurate length standard without all the fuss.

Re:Accurate distance too?

[bobdotorg]

it should be possible to measure a metre very exactly.

Ah - but I suspect that measurement of what comprises six inches will be as imprecise and inaccurate as it's always been.

Re:Accurate distance too?

[SnowZero]

Since at least the 1970s, the US system has been defined off of the metric system. A foot is exactly 0.3048 meters. Everyone wins, as normal people keep the values they are used to (to at least an accuracy they would never care about), and scientists get the exact values that they need.

Re:Accurate distance too?

[SpaceLifeForm]

That can't be accurate. I'm sure that 1 nanosecond is 8 inches. The ladies say it's less however.

Why do this?

[zerman]

I don't mean to be offensive, but is there any real point to this? How much accurate does the clock really have to be? What is the point of having a clock that is this accurate? We pour millions of dollars into this type of thing. So what? Even if we did need the accuracy (which we don't) we would never have it because the accuracy bottleneck would always be transporting the signal to wherever it's needed. Can anyone think of one good example where this clock serves any real purpose, and the old cesium one wasn't good enough?

Re:Why do this?

[Lisandro]

It won't be of any use to the regular Joe. But there's a lot of scientific experiments that rely on accurate time measurements, notably those involving relativistic effects.

Re:Why do this?

[Carthag]

I don't mean to be offensive, but is there any real point to this?

"This could lead quite soon to a new definition of the second, and in a while to improved resolution in GPS successor systems. More interestingly, there are theories that some of the universe's fundamental dimensionless constants may have changed by a parts in a million over the last 10 billion years or so. These clocks are so accurate that they should be able to detect these changes over a year or two."

Re:Why do this?

[stevelinton]

The accuracy of caesium clocks is one of the factors limiting GPS accuracy to a meter or so. These clocks could get that down to a millimeter allowing, for instance, GPS based automated guidance for trucks and automated landing for planes.

There are also applications in scientific research -- I mentioned detecting changes in fundmental constants in the story, it might also help allow very long baseline interferometry (where two radio telescopes thousands of miles apart obtain the same resolution as one telescope thousands of miles wide) at higher frequencies, pushing into the long IR.

Re:Why do this?

[maeka]

The accuracy of the clocks is a small factor in real-time GPS accuracy.

Ionospheric delay plays a much larger role. Survey-grade receivers use both the L1 and the L2 bands in an attempt to better model this delay. Ionospheric delay is frequency-dependent and impacts on the L1 and L2 signals by a differing amounts.

Multipath plays a role also, not as big as the ionosphere, but still larger than the accuracy of the clocks on the GPS satellites.

Re:Why do this?

[Sai Babu]

"A second highly-monochromatic red laser (674 nm) is then aimed at the cold ion, and tuned to two very precisely defined energy states in the cold ion. Once the laser is locked on to this precise energy or frequency interval it becomes very stable."

ASIDE: Strontium give the nice red you see in fireworks.

Physical constants are defined in terms of time. We only know that they are constants so far as we can measure the passage of time. Our model of the universe is based on constancy. With a better clock we can refine or if necessary change the model.

If you care to learn about time, take a tour of the Navel Observatory's Time Service Department.

Re:Why do this?

[Misanthropy]

I was thinking the same thing until I actually read the article.

An answer from the article that affects everyone and not just super geek physicists:

Navigation on earth - based on a cluster of orbiting satellites - is limited by the accuracy of the atomic clock on each satellite. A series of calculations can get millimetre accuracy on the position of a stationary object, but for moving objects like cars and planes the accuracy is no better than a few metres. Only by making faster measurements can this accuracy be improved, something enabled by a more accurate definition of the second.
...
"That is why GPS is not yet good enough to land a passenger aircraft on its own," Prof Gill says.


Pretty cool stuff.

Re:Why do this?

[Tony-A]

Can anyone think of one good example where this clock serves any real purpose

Predicting earthquakes and volcanos.
Finding oil, gas, mineral deposits.
Hardly automatic, but attaining extreme accuracy cheaply can only help.

With a few high precision clocks broadcasting, it is possible to triangulate position precisely and hence the delay time. Precision in timing translates into precision in distance. If stuff is moving inches per decade or century, it would be interesting to know exactly how that movement is accomplished.

Re:Great!

[Orgazmus]

Hehehehehe. *giggles*
You said time, man!

upgrade

[Barsema]

I guess this guy will need an upgrade.

Give or take a year...

[CleverNickedName]

More interestingly, there are theories that some of the universe's fundamental dimensionless constants may have changed by a parts in a million over the last 10 billion years or so. These clocks are so accurate that they should be able to detect these changes over a year or two.

Exactly how long will it take to detect these changes?

Re:Give or take a year...

[agraboso]

Fundamental constants of Nature changing over the Universe history and/or over space is a topic of debate in the physics community (in which I include myself, being a grad student in physics).

There is no compelling theoretical reason that suggests this running of the fundamental constants. There are some experimental (astrophysical) evidence that could be explained in this way, and several models have been developed. They would have far reaching consequences, changing our views on cosmology and the Standard Model of particle physics.

Pinkfud, your "simple" argument is a trivialization on the issue and doesn't make much sense, in fact. For example, no observer could stand outside the universe, because there's nothing outside the universe.

I don't know if you got your ideas from a "popularising" science magazine (don't ever trust them) or misinterpreted a more serious source. But keep researching into it, and if you got the opportunity to discuss it with a physicist, do it.

P.S.: I pretend this comment just to point to you that your understanding is incorrect and to encourage your interest for physics.

Atomic wristwatch?

[cortana]

Call me back when there's a portable version available.

Re:Atomic wristwatch?

[deglr6328]

This brings up an interesting point dosent it? How can a clock accurate to one in 10^15 or one second in 30 billion years ever be truly useful to that accuracy? Wouldn't simply walking the thing down the hall to the next lab introduce unacceptable error in the clock due to the time dilation involved?

Re:Wrist Watch?

[TeaQuaffer]

The link of which you speek is here

My favorite quote is "Batteries are included (they last about 45 minutes but are rechargeable)."

Why go any further

[suso]

1 second every 30 billion years? That's more than twice as long as the age of the universe. So why then would atomic clock developers need to go any further?

Re:Why go any further

[stevelinton]

Because they're interested in deviations of much less than a second.

Re:Why go any further

[metlin]

Because you need precise measurements for things other than needing to know what the time is.

And these clocks are not just used as solar clocks, they are calibrated to be sidereal clocks too - to know the movement of the stars and the like.

Imagine you are conducting a particle collision experiment in a tunnel - the particles are almost travelling at the speed of light, and they'd cover the distance of your tunnel almost instantaneously. You would need to measure this as precisely as you can. The more this measurement is, the more precisely we can calculate how the data from other particle collisions in the Universe (from cosmic rays, for instance) are - letting us know how the Universe has changed/is changing.

There are several applications of it - most of it of interest to physicists only, ofcourse.

Re:Why go any further

[ThJ]

Accuracy and precision are not the same, as outlined in other replies to this article. The less drift you have over time, the more accurate it is. The higher number of ticks you have pr second, the more precise it is. It would be interesting to know the number of ticks/second these things can do, though...

Re:Why go any further

[gtkuhn]

But this won't help them find deviations in physical constants even if they "find them". Unless we build dozens or hundreds of these clocks, we'll never know if the universe is changing or if there is a manufacturing defect in the clock.

Re:Why go any further

[Council]

If the universe IS changing, we'll never know from these clocks since they would also be subject to change.

Understandable first reaction but not at all true.

For one, that's saying that we can't measure changes in fundamental constants AT ALL, which isn't true. We could find that our value for G has changed over time in the fifth decimal place.

All these researchers are syaing is that we can now look for changes three decimal places further than we used to.

(Regarding the idea of measuring the change of something fundamental -- there's no reason that the effect you're measuring has to be an effect relevant to the workings of your clocks -- I can measure the fundamental constant, say, G (strength of gravity, by timing how long things take to fall), using, say, a spring-based clock (or a light clock) that is in no way dependent on G. If G changes, I'll see the change. Just because a constant is fundamental doesn't mean it has an effect on the relevant operation of my measuring device.)

Like Henry Ford said when visiting a museum

[melted]

of clocks: "I see no progress in this industry. These clocks are no faster than the ones they made a hundred years ago."

Not really new

[Dolphinzilla]

trapped ion frequency standards are nothing new, NIST made one years ago, the only difference is that NPL uses Strontium instead of Mercury. While it appears to be more accurate than the NIST one, trapped ion standards are not very practical to build or run for everyday use and its not a primary frequency standard, since the definition of the second is in terms of Cesium resonance, only Cesium clocks are primary frequency standards.

That's nice but...

[ZoneGray]

That's all well and good, but I'll bet it still flashes "12:00-12:00-12:00" after the power goes off.

Changes in Constants?

[TeaQuaffer]

There is a little blip by Chris Carilli about changes in constants. [SIC] and more detailed article here.

Does anyone know more about this?

Spring forward, Fall back

[AndroidCat]

Remember folks, turn your fine-structure constant ahead tonight before going to bed.

Re:Great!

[metlin]

No, he was right.

Accuracy is how close the measurement is to the actual value, precision is how much often the measurement is in agreement with the value.

Showing the wrong time, no matter how precise, doesn't mean much. The new clock is more accurate.

Re:running late!

[thepoch]

You must be female. I hear it the other way...

"You're a billionth of a second late! Hmph!"

Damn clocks.

Bad reporting

[fatphil]

Slashdot's error -
It's not 1000 times more accurate, it's 3 times more accurate (than the NIST's mercury ion resonator). The figure of 1000 is what they think the technology in the future, but that's purely hypothetical.

NPL's errors -
Bombarding an ion with a blue laser in order to cool it is _in_no_way_ similar to firing a beam of light at a mirror-ball. Mirror balls do not get cooler when you fire beams of light at them. Explanations that use inappropriate analogies are as useful as wearing tie-died lab-coats in night-clubs.

If "one part in 10^18" is "nearly a thousand times more accurate than the best clocks of today", then today's best clocks must be accurate to 1 part in 10^15. Therefore this new clock, being "three times more accurate than the Americans", "3.4 parts in 10^15", cannot be the be the best clock of today. Either that or someone in NPL can't do simple maths.

FP.

Re:Bad reporting

[brian0918]

Can I get +4 Insightful for catching all those errors as well? :D

Second Minute

[zenzic]

According to Silvanus Thompson in his famous (and awesome!)(c1910) calculus book the word second comes from the term "second minute".

I thought that was a neat and strange word origin (if correct).

to quote him...
"When they came to require still smaller subdivisions of time, they divided each minute into 60 still smaller parts, which, in Queen Elizabeth's days, they called "second minutes" (i.e. small quantities of the second order of minuteness). Nowadays we call these small quantities of the second order of smallness "seconds"."

Re:Second Minute

[kingkade]

Thank you for the answer to a question no one asked.

Re:Second Minute

[mattdm]

OED backs this up:

a. F. seconde, ad. med.L. secunda, fem. of L. secundus SECOND a., used ellipt. for secunda minuta, lit. 'second minute', i.e. the result of the second operation of sexagesimal division; the result of the first such operation (now called 'minute' simply) being the 'first' or 'prime minute' or 'prime' (see PRIME n.2 2)

Re:Second Minute

[JanPeterBalkenende]

From http://www.etymonline.com/:

second (n.)
"one-sixtieth of a minute," 1391, from O.Fr. seconde, from M.L. secunda, short for secunda pars minuta "second diminished part," the result of the second division of the hour by sixty (the first being the "prime minute," now called the minute), from L. secunda, fem. of secundus (see second (adj.)). Shortened form sec first recorded 1860.

So sort of true, but of course the use of second and minute as time units originates in Latin.

Re:Second Minute

[Anonymous Coward]

I guess while We're at it, Queen Elizabeth should be credited with the invention of the Time Machine as well.

According to multiple sources (see Eli Maor, Trigonometric Delights, Princeton Press, etc):

"The Greeks called the sixtieth part of a degree the "first part," the sixtieth part of that the "second part,"...

In Latin the former was called pars minuta prima ("first small part") and the latter pars minuta secunda ("second small part"),
from which came our minute and second."

The actual subdivisions are Babylonian in origen, since they invented the concept of the 24hr day
with sexagesimal units of time (hours) which were subdivided a SECOND time into 60 TINIER chunks (seconds).

Notice also that most romance languages have words for this unit of time that not only predate Queen Elizabeth's birth, but the English language itself.

Awesome

[roman_mir]

But the real question is can MS make a download status bar that is 1000 times more precise and does not go from 2 minutes to 20, then to 4 minutes, then to 5 minutes etc. Or this invention does not affect a standard Microsoft Millisecond (which I believe is a random function?)

Re:fundamental constants?

[Stevyn]

so I guess seconds should be represented as floats instead of ints?

Precisely?

[starglider29a]

I'm relativistically certain that when these articles and replies use the word "accurate", they really want to be saying "precise." Right?

I mean, 'what time is it?' to the Universe? What time WAS it 'when time began'? Was there a 'countdown to the beginning of time?' And in which Universal Time Zone are we? Are we on "Universal Light Matter Savings Time?" Was Heinlein correct? IS THERE Time Enough for Love?

Re:damn whippersnappers

[mangu]

When Galileo started timing things he used his heartbeat as a standard. No, he didn't like it. He tried to improve it, in some experients he used the rhythm of music as a time standard.

Re:Accurate clocks causing us problems

[philip_bailey]

Unfortunately the world has not completely standardized on when and how these leaps seconds are to be inserted

Rubbish. This has been standardised for many years.

WTF?

[commodoresloat]

Man that shit is complicated. No wonder we Americans never adopted the metric system. If I want to measure a yard, I don't need no fancy lasers. Just a yardstick!!

Re:this might be a stupid question but...

[blueg3]

It's an awful point. When you build atomic clocks, you're not interested in measuring how long it takes the earth to go around the sun to great precision. You're not interested in actually keeping time for the next 30 billion years accurate to a second.

For that matter, if the talk I heard a year ago about the work at NIST on this very thing is still true, these atomic clocks can't maintain their accuracy for more than a week or so.

The "one second in 30 billion years" is a convenient extrapolation so that non-scientific persons get an idea of how accurate it is. It would be more correct to say that the atomic clock, in situations of normal operation, is accurate to one part in 10^18.

For that matter, it doesn't hold a wall-clock type value, like saying it's exactly 22:04:17.832... Our choice of reference for time (say, when "noon" is), is difficult to measure and quite arbitrary. Instead, you're interested in, say, how long a particular process takes (light making a round trip, or atomic decay), measured to a very high degree of accuracy (and precision).

Of course units of time are arbitrary. All units are arbitrary. Dimensions (length, time, etc.) and fundamental constants are non-arbitrary, but don't have any "natural" expression in terms of the units we use. (The most natural system of units is arguably expressing everything in terms of fundamental constants.) Seconds, minutes, hours, and years have arbitrary definitions for our convenience, just like any other unit.

I have an even more accurate clock..

[adeyadey]

..in my bedroom. It has stopped, and shows *exactly* the right time twice a day.

This "accurate" clock you describe is only exactly right every few billion years..

Re:Atomic Clock Radio Accuracy

[anno1602]

No. Radio-controlled clocks are not that accurate. Keep in mind that they are not actually constantly synchronized with the national atomic clock, they are running on a standard quartz and reset themselves every time they successfully receive a time signal. Besides, a factor would also be the results of the signal being reflected all over the place, potentially traveling a much longer path than a straight line - and, due to moving objects such as cars that might be in the way, not always the same paths. Besides, it would be impossible - ntp uses two-way communication to measure the lag, while radio controlled clocks can't phone home to the atomic clock.

So, can someone please tell me...

[WasterDave]

This has been bugging me for years. There's this spurious "atomic clocks are accurate to 1 second within a million years" thing - so how the hell to you measure it? And if you've got a more accurate way of measuring time, why not just use *that* as the clock.

I know there's an answer, please enlighten.

Cheers,
Dave

Re:So, can someone please tell me...

[zwalters]

Sorry for all the posts: I now really hate the "HTML formatted" box.

The standard press description is a little confusing. A good way to think about the subject is that atomic clocks are extremely good frequency standards, which incidentally makes them good time standards as well (if I have a pendulum that oscillates once per second, I can measure time by counting the number of oscillations).

The idea behind all atomic clocks is that atoms are very picky about the kinds of light they absorb and emit (that's how astronomers can tell what kinds of atoms make up stars). There are some frequencies of light that interact very strongly with any given kind of atom, and some frequencies where the light barely interacts at all. When the atom absorbs a photon, it jumps to a higher energy state, when it emits a photon, it jumps to a lower energy state.

If you look carefully at the spectrum of light that an atom absorbs or emits, you'll find that the atom isn't equally picky about every kind of transition that it can make. There are some transitions (in cesium, they're called hyperfine transitions) where the atom isn't just picky, it's positively fastidious. What you'll find is that if you want to excite these transitions, you'll have to shine light that is exactly the right frequency, plus or minus a tiny amount (the "linewidth" -- literally, if you plotted absorbtion vs. frequency, the width of the peak you would see on the graph.)

So reasoning backwards, if I'm shining a laser at a cavity of cesium atoms and I measure that they're strongly absorbing the light, then I know the frequency of the laser has to be *exactly* the frequency that excites the atom, plus or minus a tiny linewidth. So I can count the oscillations of my laser and figure out how much time has elapsed. That's basically how an atomic clock works.

But if you wanted to get really anal about it, you could point out that I really don't know the exact frequency of my laser at all -- all I know is that it's the frequency of the atomic transition, plus or minus the linewidth. So if a hypothetical Alice and Bob in adjacent laboratories had lasers locked to the same transition, it's possible that Alice could have her laser locked at the atomic transition frequency minus a linewidth, while Bob has his locked at the atomic transition frequency plus a linewidth. (The linewidth was chosen to be really small, but it's still not zero: also, really narrow lines are hard to lock a laser to, so there's always a tradeoff involved.) So Alice and Bob's clocks will drift a tiny bit relative to each other. But because the linewidth is so small, it will take an insane number of oscillations before Bob measures that one more second has passed than Alice measures. The "1 second in 30 billion years" is just a reflection of this: it measures the linewidth of the transition relative to the frequency of light involved.

The appeal of using Mercury or Strontium atoms (small world: one of my best friends is also working on a Strontium time standard) is that they have a special transition that is even narrower relative to the transition frequency than Cesium's hyperfine transition.

Re:Accurate clocks causing us problems

[certsoft]

As the other post has noted, leap second insertion is standardized. In addition, there hasn't been a leap second since December 1998, and there will be none for at least the rest of this year.

Definition of precision?

[yodaj007]

If some clock is held to be the standard, how can they say that its off by so many seconds every so many thousand years? By what standard is the standard held to?

Re:Wrist Watch?

[Detritus]

They are nowhere near as accurate as an atomic clock. Even with a lab grade radio clock, large amounts of error are introduced by the propagation delay of the radio signal, which isn't constant. Consumer grade radio clocks are useless for any serious applications. They use cheap quartz crystal oscillators and compensate for errors by resetting the clock once a day.

Re:How do they know?

[Detritus]

Hydrogen masers have better short-term stability than cesium frequency standards, so one can compare the two and measure the short-term variation in the frequency of the cesium standard.

Clocks can also be run in groups. With some mathematics, the group can produce a result that is more accurate than a single clock.

If you have a detailed knowledge of the physics involved in the operation of a clock, the possible sources of error can be modeled and predicted.

Re:Compared to what?

[Detritus]

The Earth is a lousy time standard. The international atomic time scale (TAI) does not have leap seconds and is not synchronized to the movement or rotation of the Earth. Civil time (UTC) has leap seconds to keep it synchronized with the Earth's rotation. This is for the convenience of people who use it for navigation.