New Most Precise Clock Based On Aluminum Ion

eldavojohn writes "The National Institute for Standards and Technology has unveiled a new clock that will 'neither gain nor lose one second in about 3.7 billion years,' making it an atomic clock twice as precise as the previous pacesetter, which was based on mercury atoms. Experts call it a 'milestone for atomic clocks.' The press release describes the workings: 'The logic clock is based on a single aluminum ion (electrically charged atom) trapped by electric fields and vibrating at ultraviolet light frequencies, which are 100,000 times higher than microwave frequencies used in NIST-F1 and other similar time standards around the world.' This makes the aluminum ion clock a contender to replace the standard cesium fountain clock (within 1 second in about 100 million years) as NIST's standard. For those of you asking 'So what?' the article describes the important applications such a device holds: 'The extreme precision offered by optical clocks is already providing record measurements of possible changes in the fundamental "constants" of nature, a line of inquiry that has important implications for cosmology and tests of the laws of physics, such as Einstein's theories of special and general relativity. Next-generation clocks might lead to new types of gravity sensors for exploring underground natural resources and fundamental studies of the Earth. Other possible applications may include ultra-precise autonomous navigation, such as landing planes by GPS.'"

Comments

Ah, I unplugged the atomic clock...

[tjstork]

I unplugged the atomic clock by mistake. I was just brooming around and I knocked out this here plug. Anyone know what time it is?

Re:Ah, I unplugged the atomic clock...

[sconeu]

Does anybody really know what time it is?
Does anybody really care?

Re:Ah, I unplugged the atomic clock...

[Kozar_The_Malignant]

Sorry, but it's Friday, and it's five o'clock somewhere.

Re:Ah, I unplugged the atomic clock...

[PatHMV]

Does anybody really know what time it is? Does anybody really care?

25 or 6 to 4...

Re:Ah, I unplugged the atomic clock...

[deglr6328]

The long list of lame jokes that would inevitably accompany this article are obvious and unsurprising. But these "oooh now I can get to my next meeting within one yoctosecond of it starting" jokes may be more apt than you realize. There is a real issue of how to even use a clock this accurate at all. This new Al ion clock is supposedly accurate to one part in 10^17, yes? An article I read in SciAm ~8 years ago predicted this milestone would be reached within the decade, and it seems they were right. The problem is, you will introduce a relativistic time dilation to a clock with an accuracy on the order of 1 in 10^17 merely by walking down the street with it. Similarly, you will experience a comparable magnitude of time dilation by reducing the earth's gravity you experience by raising your elevation off the ground by only 10 centimeters. Aside from pure physics experiments like measuring a potential variation in the fine structure constant since the beginning of the universe and such, I don't know how practical application of a clock this accurate could be achieved. For instance, even if you manage to get a time standard of this level accuracy aboard a GPS satellite, you need to know the satellite's location in orbit, it's "ephemeris data", to an equal degree of accuracy in order to make use of such a time standard. Is that even possible? How do you transfer a time standard of such extreme precision between two clocks while preserving its integrity? If that can't be done, what is the practical use of an absolutely stationary clock that can never be moved? Even for the measurement of the fine structure constant at something like 1/10^18, you will have to take into consideration the movement of the continent due to plate tectonics and the movement of magma bubbles in the planet's mantle in order to have confidence in the accuracy of your answer.

Re:Ah, I unplugged the atomic clock...

[jmizrahi]

You are absolutely correct, the time measured by such a clock is going to be dependent on general relativistic effects, most prominently by distance from the mean geoid. However, I fail to understand how you jump from that to concluding that it's useless. For example, you could use such a clock to make precision measurements of general relativity and test possible extensions. Moreover, a clock that sensitive should be able to "feel" changes in gravity caused by density fluctuations in the Earth. This could help find oil deposits, for example. The summary says as much. Generally speaking, you NEVER lose by increased precision. It is true that if your specific application is limited by low precision in some other component, you won't gain by increasing precision somewhere else. However, that's not the case here. I'll admit that I don't know enough about GPS and satellites to answer your specific question, but my impression is that they currently ARE limited by time standards.

Re:Ah, I unplugged the atomic clock...

[IICV]

Allright then - you take twelve of these clocks, grouped into clusters of three, arranged in the shape of 3D right angle with each cluster as far away from the other as possible. You isolate them as well as you can, so that they are not disturbed by local vibration and other such things. Probably the best thing to do would be to launch them into space.

Then you measure their time differences.

If there's any differences, assuming you've isolated them well enough and are filtering out the expected noise, those differences must be due to external gravity waves.

Tadaa, we've got a gravity wave antenna. Maybe someone's talking in that spectrum.

Re:Ah, I unplugged the atomic clock...

[IICV]

I'm smoking 100% pure grade-A science, son.

Extraordinary claims

[Locke2005]

The National Institute for Standards and Technology has unveiled a new clock that will 'neither gain nor lose one second in about 3.7 billion years' Sure, they say that now, but just TRY tracking them down to get your money back 3.7 billion years from now when you find out they were lying!

Re:Extraordinary claims

[pnewhook]

Or if they move it. Once they do general relativity takes over and the time is now 'wrong' according to a stationary observer.

Marketing angle

[sakdoctor]

For the domestic market they can use the marketing angle that aluminium is safer than mercury, and that it will case less pollution when you come to trade it in.

In fact, I think I'll order one now.

Re:Marketing angle

[RealErmine]

For the domestic market they can use the marketing angle that aluminium is safer than mercury, and that it will case less pollution when you come to trade it in.

In fact, I think I'll order one now.

Everyone knows that aluminum is an intermediate material in terms of durability and weight reduction. Wake me up when it is replaced with carbon fiber.

It's about time

[Switchback]

Well this is money well spent. I mean, having to correct my clock every 100 million years was becoming just too laborious.

Plane landings?

[Dynedain]

If you need a clock that's accurate to 8.6 x 10^-19 seconds in order to land a plane, you're probably doing it wrong.

Re:Plane landings?

[ircmaxell]

You need that kind of precision to do it from several hundred miles away (As is what happens with GPS). The Satellites all have clocks on board that are synchronized and constantly transmit the time. A GPS receiver simply needs to listen to a few of the satellites, and compute the difference between their times to determine the location. The kicker of it is that since the satellites are moving at fast speeds (relative to us), the time of their clocks are different from "our" time. So special relativity is used to counter those relativistic effects. So basically, GPS is only as accurate as the clocks that form its backbone. That's one of the reasons why unaugmented GPS is limited in accuracy to a few meters. Improving the accuracy of the clocks (by orders of magnitude) has the potential to cut down a few meters to potentially tens of centimeters... You'd need that level of accuracy to land a plane... Planes "flare" during landing (slowing the rate of decent to nearly 0 just as the wheels touch down). Plus or minus even one meter in any direction (up, down, forward, back, side to side) could be catastrophic. So current "autoland" autopilots use radar altitude and ground based ILS (radio based navigation) to gain the necessary precision. If GPS accuracy gets good enough to where you don't need those aux systems (or need them as primary at least), complexity of autopilots would drop significantly...

Re:Plane landings?

[Burdell]

The relativistic speed means their clocks run slower than clocks sitting still on Earth, according to special relativity. Another source of GPS time difference is that they are farther away from the center of Earth's gravity than we are, so according to general relativity, their clocks run faster than clocks on Earth. Both factors have to be taken into account.

Re:Plane landings?

[ircmaxell]

Correct, which is why I said in my post that ILS and radar altitude are needed at the present time. Radar altitude systems are prohibitively expensive and big (pretty much only usable on commercial airliners and in military applications). ILS is good for approach, but you can't land off it. It'll get you down to 50 feet AGL (or less in certain areas), but it won't get you though the flare. That's because the glideslope portion of the ILS signal is set a 3 degrees. So it can only tell you your relation to the 3* slope, not distance above the ground (which is what's really needed when you're over the threashold). ILS gets you aligned with the runway, and onto the proper approach path. It's an approach system, not a landing system (and was never designed as such)... For an ILS system without a radar altimiter, the pilot always must handle the actual landing. (hence the classes of autopilot, and existence of a decision height -- The height which you need to either be able to proceed visually, or abort the approach)... That's why autoland based on GPS is such an interesting thing. It would enable cheaper autoland systems which are a lot smaller than present systems (Basically business jets and light aircraft could potentially be equipped) and don't depend on airport infrastructure. So you could theoretically autoland on a small General Aviation airport...

I do have my Private Pilots license with Instrument rating, but I also love physics...

Re:Plane landings?

[plover]

But his assumption that clock error is responsible for all of the current lack of precision is wrong. Clock error is responsible for probably less than a third of the current error. Atmospherics, multipath reflections, and ephemeris errors account for the bulk of the error.

Sure, every improvement is an improvement. But these clocks are not a magic bullet that will magically grant centimeter precision.

Re:Plane landings?

[blueg3]

Red and blue shift are not caused by moving faster than the speed of light in the local medium (though Cherenkov radiation is), but rather by motion of the emitting object relative to the observer. (Not to mention cosmological and gravitational shifts.)

Re:Plane landings?

[mpe]

Improving the accuracy of the clocks (by orders of magnitude) has the potential to cut down a few meters to potentially tens of centimeters... You'd need that level of accuracy to land a plane... Planes "flare" during landing (slowing the rate of decent to nearly 0 just as the wheels touch down). Plus or minus even one meter in any direction (up, down, forward, back, side to side) could be catastrophic. So current "autoland" autopilots use radar altitude and ground based ILS (radio based navigation) to gain the necessary precision.

"Full blind autoland" systems have been around since the 1960's An unexpected problem with the first systems is that they were "too accurate", runways wear out quickly if touchdown always happens in the same place.

If GPS accuracy gets good enough to where you don't need those aux systems (or need them as primary at least), complexity of autopilots would drop significantly...

Most landings are performed by pilots. Even in an autoland situation the pilots go through similar procedures to if they were flying the plane. Otherwise things are likely to end up like TK1951.

Re:Assuming We're still around

[Locke2005]

Uh, I think what they really mean is that it is accurate to about one four-billionith of a second per year, which beats the heck out a Timex. I don't think anyone seriously believes the device itself will last long enough to lose or gain even a microsecond.

3.7 billion years from now ...

[Korbeau]

neither gain nor lose one second in about 3.7 billion years

Location: 3.7 billion years from now, early December, Planet Earth

Doomsayer: "The ancient "Scientific Community" civilization was so certain a great cataclysm would come in the following months based on their long-lost primitive yet poweful and mythical calculations that they even deemed unnecessary to keep track of time correctly starting this age! The end is near my friends! A new age will come!"

You're late

[spun]

You should have been here to welcome us .0000000001 seconds ago. Your membership in the Committee to Welcome Our New Overlords has been revoked.

Even Better

[causality]

For those of you asking 'So what?' [ ... ]

Do you have any idea how many Slashdot articles could benefit from such an explanation?

Re:So I guess this means

[alexj33]

will 'neither gain nor lose one second in about 3.7 billion years,'

What clock are they going to check it against to verify its accuracy?

And if there is such a clock, why isn't that clock being tested instead?

The Star Trek Fanatic version

[sacrilicious]

"My god... transparent... ALUMINUM?"
"No no, this is *timekeeping* aluminum. You see, it consists of an incredibly preci-"
"Traaaaaansparent aluminum... amazing."