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Keeping Time with a Mercury Atom
Roland Piquepaille writes "The National Institute of Standards and Technology (NIST) has announced that a new experimental atomic clock based on a single mercury atom is now at least five times more precise than NIST-F1, the U.S. standard clock. This mercury atomic clock 'would neither gain nor lose a second in about 400 million years' while it would take 'only' 70 million years to NIST-F1, based on a 'fountain' of cesium atoms, to gain or lose a second. But even if this new kind of optical atomic clock is more accurate than cesium microwave clocks, it will take a while before such a design can be accepted as an international standard. A ZDNet summary contains pictures and more details about the world's most precise clock."
syncing to time.singlemercuryatom.nist.gov doesn't work yet.
?giS
It's easy to make impressive statements like that when you know nobody will be around to prove you wrong!
bite my glorious golden ass.
I officially throw open this whole topic to be used for
bitching about Roland Piquepaille.
Great news for those mission critical D-Link routers!
So you're going to trust a single mercury atom to keep time acurate for 400 milliion years even though the half-life is only 444 years? Oh, wait a minute. The planet Mercury is being used for this new clock. For a split second, I thought we had a serious technical problem.
They're treating time as if it were something absolute.
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So... at what point do you say that a clock is accurate enough? I mean, yeah maybe this thing is more accurate than current technology, but if it turns out to be way more expensive, why bother? How often do you need the accuracy that current technology can't provide?
DRM 'manages access' in the same way that a prison 'manages freedom'
Roland is back with the accepted stories you wish you'd submitted, and no one is wasting time with any bullshit about how he's robbing us with his good editing.
--
make install -not war
Can someone explain why we even need this sort of precision?
Duct tape is like the Force. It has a light side, a dark side, and it holds the universe together.
While a 70 million to 400 million jump is quite exceptional, how long will this continue? Will anyone really want to use a clock that won't lose a second until AFTER the sun has expanded and burnt up the earth (~5 billion years)?
Why is it that cars break in 15 years, and most other things are extremely fragile, but this clock can last 40 billion years? Is it made from some kind of super-dense material? Why is the quality of this timepiece so great, and how is it made? It would be nice to have some technical information on how an ordinary person could manufacture a timepiece of this exact precision. Are the materials from a very deep mine? Are they hydrogen materials? Why is this clock so accurate?
...from the Heisenberg uncertainly principle:
The more precisely
the MOMENTUM is determined,
the less precisely
the POSITION is known
So this clock is unfortunately missing. And when it is found, it is not so accurate anymore.
"Fix it"
400 million years in the future, my descendents will profit unthinkable amounts from their ownership of y400002k.com
Just in case the religious right get a further hold on our country in the future, I've also registered jesuswillreturn400002k.com and (hedging my bets) spaghettimonsterwillreturn400002k.com
but we all know that by that time, humanity will simply be slaves to the powerfully accurate mercury clock.
So, I for one welcome our new mercury atom overlords, and remind them that mercyatomoverlords.com can be had for the steal of 6.7 billion dollars, should cover the cost of registering the domain up to that point.
www.GrenadeHop.com
Teacher: What! You're 15 attoseconds late! Again! Go stand in the corner!
-- Cheers!
Fit on my wrist??????????
How do you calibrate a new atomic clock, if you have nothing more accurate to compare it against? And if we have clocks that won't lose or gain a second in 70 million years, why do we need to develop one that won't lose or gain a second in 400 million years?
or should I even care how many MILLIONS of years it takes a clock to get thrown off by an entire second?
70 million years is more than enough time for me... Sounds like somebody needs more grant money to me!
Remember, adding a random "do:loop" into someone else's code is a damn good time!
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I'm just curious about something here. If a second is defined to be 9,192,631,770 oscillations of a Caesium-133 atom, then why is it said atomic clocks are accurate to within a second over 70 million years? Isn't that lost/gained second itself defined by the Caesium atom's transitions? I hope this question makes sense...
--- At my sig, unleash hell.
At what point do people simply say that our time keeping methods are good enough?
We already have a clock that only loses 1 second every 70 million years! The odds of the current time keeping system (or mankind, for that matter) continuing in it's current form for the next 70 million years are rather low, so why do we really need one that only loses a second every 400 million?
Sure, it's nice to be able to improve, but can't the research money go to something more useful? Like, maybe cancer research or studies into how we can build giant robots that transform into dinosaurs...
I'm keeping time with empties.
I'm suspecting that this level of accuracy would be quite useful in high-end scientific experiements--not so much for general wall-clock settings.
For example, measuring the duration of extremely short events--like in particle accelerators.
- The race is not [always] to the swift, nor the battle to the strong. -
This reminds me of that one clock that someone wanted to stick into a New Mexico cave or something. It was big, mechanical (IIRC) and had a foot pedal that you stepped on to update the display.
The details in my head are sketchy, but I think there was a Slashdot article on it. Maybe it wasn't. Anyway, this reminds me of it.
"Beware of he who would deny you access to information, for in his heart he dreams himself your master."
How do you determine that it will gain or lose a second in 400 million years instead of 70 million years if:
A.)It hasn't been around long enough to find out.
B.)There are no timepieces more accurate to base this estimate on.
Can't wait to have a wristwatch with this. My atomic wristwatch is a bit too bulky.
Open Source Alternatives
For any definition of a fundamental unit, there are (quantum-mechanical or practical) limitations on how accurately the specified measurement can be made. Thus, there is a small but finite spread in the effective values used by different laboratories. As long as the new standard is within that range, it is "exactly the same" in the sense of being indistinguishable, but nonetheless better, because its measurement uncertainty is smaller.
Whenver the definition is revised, the new proposed standard is compared to the old accepted standard as precisely as anyone has ever done. For example, Louis Essen measured the frequency of the Cesium hyperfine transition as 9,192,631,770 +/- 20 Hz relative to the old tropical year definition. Thus, 9,192,631,770 was picked as the definition.
However, there are quantum mechanical limitations on our ability to measure that. In particular, when we examine the atoms for a time t, there is an uncertainty proportional to 1/t in the frequency. With cesium atoms, which are electrically neutral, gravity poses a problem. There's no way to hold them up without disturbing them, so they fly through cesium beam clocks in a fraction of a second, giving a small uncertainty in the measurement frequency. Suppose this is +/-1 Hz; that then leads to an uncertainty of +/- 1/9192631770 in the duration of a second.
Cesium fountains slow the cesium atoms down as much as possible and thereby extend the measuring time and reduce the uncertainty. However, for any given measuring time, a higher frequency will always lead to a smaller relative uncertainty. The problem is that 9 GHz is accessible to fast electronics. The mercury clock generates a frequency of 1,064,721,609,899,143 Hz (+/-10 Hz as of current measurements) - that's 1.065 Petahertz! There's no electronics that can keep up, so the challenge of building such a clock is measuring its output frequency. Nonetheless, it should be obvious that with a base frequency some 100,000 times higher than the base frequency of a cesium clock, the potential measurement uncertainty is 100,000 times lower.
If the standard second is ever redefined, it will be to a value that is indistinguishable from the old one using any cesium clock ever built.
It's like drawing a line. Suppose you have a line in pencil, and need to know where it is as precisely as possible. After a while the width of the pencil gets annoying, so you sit down with a magnifying glass and measure it as precisely as possible, and draw a line with a super-sharp pen through the middle of the pencil line. But then that's too wide and fuzzy, so you use a microscope and score a line with a diamond-tip probe. But then that's too wide, so you use an atomic-force microscope and push individual atoms around. Then the atoms are too fuzzy, so you cryogenically cool it to reduce their motion. Etc. etc. Each standard is equal to the old one because it's inside the range of uncertainty of measurement.
Alright, so if we have a clock that loses a single second every seventy million years, why not just move it a second every 70 million years and end up with a clock that (should) be 100% accurate?
All niggers are indeed faggots
So why does the page say:
"Jim Bergquist's optical clock team produced the first optical atomic clock based on a transition of a single mercury (Hg+) ion in 2001. The newest single-ion clocks, using either Hg+ or aluminum (Al+) ions, show the best time-keeping performance ever measured, neither gaining nor losing a second in a billion years."
I'm confused...
Looks like Roland Piquepaille failed to RTFA?
I hear a lot of people asking why we need this much accuracy. I'll give you a hint, it's not so we'll know the time in 700 million years, it's so we'll know it now. Some years ago an expirament was carried out where an atomic clock was loaded on a plane and flown around for hours. When it landed again the clock on board was compared with a clock on land and the limit of the accuracy of clocks showed a difference predicted by relativity. Now imagine if we could add some decimal points to that difference, not just substantiate current theory, but look for subtle differences. It's a hell of a lot cheeper than building giant ring accelerators or firing off expencive rockets which the nerds (a term of affection) here seem to support.
Don't mess with the bunny, outsideworld.org
http://www.leapsecond.com/pages/atomic-bill/
Wait, so the White Rabbit is always in a hurry, but it's the Mad Hatter who has the accurate clock?
--- Jason Olshefsky
Karma: Poser (mostly affected by adding this line long after everyone else did)
Do we really need a more precise clock ?
I mean, can't we just bury some notes about Leap Years somewhere for anyone that's around in 70 million years ?
The dinosaurs are about 65 million years older than us right ? Look how far the world has come. Hell, I'll bet whatever is living here 65 million years from now will have built-in clocks in their brains anyway.
Wanna fight ? Bend over, stick your head up your ass, and fight for air.
"I don't feel tardy."
When you're trying to measure gravity waves.
Because you can - or because you should?
Daniel Kleppner of MIT contributed an article to Physics Today which ruminated on the problems that clocks like this will have for international timekeeping. The trick is that the clocks will be able to see the diurnal variations in general relativistic gravitational potential. No two clocks like this on the surface of the earth will ever be able to agree with each other. A whole new set of computational protocols for combining their results into International Atomic Time (TAI) will be necessary.
I know I'm risking my own karma to ask this, but why was parent modded Redundant? The comment is funny, and it accurately illustrates why we might take time to do something seemingly useless. Because it might be useful, duh!
Point is - parent should be modded up/funny. If I had mod points today I'd do it myself.
So you can laugh all you want to...
Ooooh, so that's why people who tend to be more active (on the move) live longer!
Half the time I'm right, the other half you're wrong.
I'll take it!!! Look at all the money I'll save going to the gym!! Whooo Hooooooooooooooo
Let's get going and change the standard. We're losing femtoseconds as I type this!
(T>t && O(n)--) == sqrt(666)
Here's a brief article (and a picture) of the US's current standard. There's also a graph showing that the US standard tends to be replaced roughly every 5-10 years.
As a measurement geek, I can tell you couldn't be more wrong.
The problem is: Ok, now you have 1/10,000,000 of the pole-to-equator distance in 1791. Now WTF is that? How much exactly? Have you ever seen two rulers where an inch are exactly the same size? If you measure your ruler WRT the meter, and then another ruler WRT the first ruler, etc, etc, the error will accumulate, and soon you'll have an inch with 2cm and another inch with 3cm. And no pieces of nothing will fit together: imagine if the pins in your computer's processor with 1/10mm error in the distance between them would fit in the socket (answer: NO)
So, we define all units in terms of thing we can measure again and again and again with minimum (preferably zero) error. (do you know that the 1m platinum bar, made two centuries ago, lost almost 1/10 mm already due to some oxidation or somesuch?)
And: temperature is not something you see in a thermometer, it's the mean speed of the molecules vibration. It HAS a meaning.
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
The server at ZDNet has crashed. I posted the text below.
Thanks for clicking,
Roland
Keeping time with a mercury atom
Posted by Roland Piquepaille @ 10:07 am
Digg This!
The National Institute of Standards and Technology (NIST) has announced that a new experimental atomic clock based on a single mercury atom is now at least five times more precise than NIST-F1, the U.S. standard clock. This mercury atomic clock "would neither gain nor lose a second in about 400 million years" while it would take "only" 70 million years to NIST-F1, based on a "fountain" of cesium atoms, to gain or lose a second. But even if this new kind of optical atomic clock is more accurate than cesium microwave clocks, it will take a while before such a design can be accepted as an international standard.
An experimental atomic clock based on a single mercury atom is now at least five times more precise than the national standard clock based on a "fountain" of cesium atoms.
The experimental clock, which measures the oscillations of a mercury ion (an electrically charged atom) held in an ultra-cold electromagnetic trap, produces "ticks" at optical frequencies. Optical frequencies are much higher than the microwave frequencies measured in cesium atoms in NIST-F1, the national standard and one of the world's most accurate clocks. Higher frequencies allow time to be divided into smaller units, which increases precision.
The NIST Time and Frequency Division built a first prototype of such a mercury optical clock six years ago. But now, this single atom based optical clock is the world's most precise one.
The current version of NIST-F1 -- if it were operated continuously -- would neither gain nor lose a second in about 70 million years. The latest version of the mercury clock would neither gain nor lose a second in about 400 million years.
Here is a picture of this experimental optical clock (Credit: NIST). This image comes from the Spring 2006 issue of JILA Light & Matter, a publication from NIST (PDF format, 8 pages, 1.52 MB). This clock is described on page 6 in "Partnership in Time."
The mercury atomic clock from NIST
Jim Bergquist's optical clock team produced the first optical atomic clock based on a transition of a single mercury (Hg+) ion in 2001. The newest single-ion clocks, using either Hg+ or aluminum (Al+) ions, show the best time-keeping performance ever measured, neither gaining nor losing a second in a billion years.
And below is a picture from Jim Bergquist holding "a portable keyboard used to set up the world's most accurate clock. The silver cylinder in the foreground is a magnetic shield that surrounds a cryogenic vacuum system, which in turn holds the heart of the clock, a single mercury ion (electrically charged atom). The ion is brought to rest by laser-cooling it to near absolute zero (Credit: Geoffrey Wheeler, NIST)
Setting up the mercury atomic clock from NIST
For more information about this optical atomic clock, please read another NIST document, How the Mercury Clock Works.
The latest research work on this clock has been published by Physical Review Letters under the title "Single-Atom Optical Clock with High Accuracy" (Volume 97, Number 2, Article #020801, July 14, 2006). Here is a link to the abstract.
Finally, you might want to know if such an accurate clock is useful for. After all, there is only a very small chance that you're there in 400 million years. Let's return to the NIST news release for a conclusion.
Ultra-precise clocks can be used to improve synchronization in navigation and positioning systems, telecommunications networks, and wireless and deep-space communications. Better frequency standards can be used to improve probes of magnetic and gravitational fields for security and medical app
once the environmentalists find out they'll make sure we can't get them - mercury is toxic after all.
...the future crusty old bastards are already drinking the Kool-Aid.