Slashdot Mirror
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."
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.
Because they're interested in deviations of much less than a second.
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.
Does anyone know more about this?
Sola Deo Gloria!
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.
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.
Also FatPhil on SoylentNews, id 863
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"."
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.
There is no place like ~!
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.