NIST Ion Clock Sets New Record for Most Accurate Clock in the World (nist.gov) 18
NIST: There's a new record holder for the most accurate clock in the world. Researchers at the National Institute of Standards and Technology (NIST) have improved their atomic clock based on a trapped aluminum ion. Part of the latest wave of optical atomic clocks, it can perform timekeeping with 19 decimal places of accuracy.
Optical clocks are typically evaluated on two levels -- accuracy (how close a clock comes to measuring the ideal "true" time, also known as systematic uncertainty) and stability (how efficiently a clock can measure time, related to statistical uncertainty). This new record in accuracy comes out of 20 years of continuous improvement of the aluminum ion clock. Beyond its world-best accuracy, 41% greater than the previous record, this new clock is also 2.6 times more stable than any other ion clock. Reaching these levels has meant carefully improving every aspect of the clock, from the laser to the trap and the vacuum chamber.
The team published its results in Physical Review Letters. "It's exciting to work on the most accurate clock ever," said Mason Marshall, NIST researcher and first author on the paper. "At NIST we get to carry out these long-term plans in precision measurement that can push the field of physics and our understanding of the world around us."
Optical clocks are typically evaluated on two levels -- accuracy (how close a clock comes to measuring the ideal "true" time, also known as systematic uncertainty) and stability (how efficiently a clock can measure time, related to statistical uncertainty). This new record in accuracy comes out of 20 years of continuous improvement of the aluminum ion clock. Beyond its world-best accuracy, 41% greater than the previous record, this new clock is also 2.6 times more stable than any other ion clock. Reaching these levels has meant carefully improving every aspect of the clock, from the laser to the trap and the vacuum chamber.
The team published its results in Physical Review Letters. "It's exciting to work on the most accurate clock ever," said Mason Marshall, NIST researcher and first author on the paper. "At NIST we get to carry out these long-term plans in precision measurement that can push the field of physics and our understanding of the world around us."
Eternity (Score:5, Funny)
The Devil: This is where you will spend eternity winding the clock
Me: Akshually I'll be winding the frequency standard; it requires additional mechanism to keep time
The Devil:
The Devil: You know that's why you're here, right?
Accuracy vs Precision (Score:1)
Ultimately how do we determine that a clock is 'accurate'?
It is no longer related to the earth's rotation, which is several fractions of a second different.
OK it it's something like 1/9,192,631,770 of a vibration of a cesium atom, but that begs the question of who decided that a second was 9,192,631,770 cesium vibrations long.
In the end, something must be arbitrary.
Re: (Score:2)
Simple: By cheating! You just define that the Caesium vibrations are totally accurate and then you measure against that.
BIPM (Score:2)
OK it it's something like 1/9,192,631,770 of a vibration of a cesium atom
This was decided by the International Bureau of Weights and Measures [bipm.org] which manages SI units. However, this definition is no longer sufficient since Caesium clocks are much less accurate than the current generation of ion clocks like the one in the paper. I believe there is a process underway to redefine the second more precisely presumably using this new technology since the Caesium-based definition is no longer sufficiently accurate, so in this case you are more worried about precision since your accurac
Re: (Score:2)
I think the underlying assumption is that the vibration of the caesium atoms is perfect. In that sense, defining the second based on that measure if perfectly fine; it's our ability to measure that has the imprecision. In the case of caesium clocks, what
Re: (Score:2)
I think the underlying assumption is that the vibration of the caesium atoms is perfect.
No, it is based on the observed, not assumed, stability of the caesium oscillation. This is directly observed by comparing multiple caesium clocks, and seeing them drift out of alignment. No assumption of perfection is involved anywhere.
Re: (Score:3)
Ultimately how do we determine that a clock is 'accurate'?
There's no such thing as accurate per-se only more accurate and less accurate. More accurate means less drift and less jitter.
but that begs the question of who decided that a second was 9,192,631,770 cesium vibrations long.
Who? International agreement, on the recommendation of some very nerdy metrologists. You need some repeatable arbitrary thing, and that definition was the most repeatable thing people knew of in 1967.
In the end, something must be a
Re: (Score:2)
Between that and acknowledging the organic lack of accuracy we call leap years, ask yourself; does it really fucking matter?
It does if you want GPS to work.
Re: (Score:2)
It's hardly dependent on any single clock.
Tell me you don't understand how GPS works without telling me you don't understand GPS.
It's like living in a house with five very accurate clocks. If you don't pick one and set all the others to the same time, you'll never agree on what time it is.
Re: (Score:2)
Between that and acknowledging the organic lack of accuracy we call leap years, ask yourself; does it really fucking matter?
You're confusing absolute time and relative time. No one gives a shit what time and date it is with any precision. What we care about is the passage of time relative between devices and between arbitrary points.
Your lack of understanding of how GPS works is the reason why you can't understand this. Without atomic clock level of precision (GPS relies on using multiple rubidium oscillators to function) you can't triangulate your position in relation to ephemeris data.
Re: (Score:3)
And if you shift the vertical distance of your watch by 5 mm you will be out of sync with the ion clock due to the difference in gravitational time dilation.
Meh (Score:3)
Re: (Score:2)
What was even more interesting was adding pennies to the pendulum made it swing faster.
By adding the pennies near the top of the pendulum it moved the center of mass slight higher and thus minutely sped up the swing. I love horology.
To quote Mr. Harrison... (Score:2)
"It's all in your mind, you know."