Scandium-based nuclear clocks promise punctuality for next 300 billion years Set your watches! Scientists have set the clock ticking for the development of a new generation of timepieces with accuracy of up to 1 second in 300 billion years or about 22 times the age of the universe. Researchers working at European XFEL X-ray have examined the potential of scandium as the basis for nuclear clocks, long …
> accuracy of up to 1 second in 300 billion years
Given the claim to accuracy, a time limit of 300 billion years sounds a little approximate. You'd kinda hope that the people who made that forecast would be able to nail down the limit of that 1 second accuracy a bit closer. Say to 316,952,044,811.3503559017 years
Unfortunately it doesn't look like the universe will osscilate. All the math is tending towards an infinite universe, but one stretched so thin that atoms can no-longer hold themselves together.
The lower bounds for the Big Rip are only 100 billion years or so, so these clocks will still be good for that. The upper bounds are out in the 10^12 years sort of number, by which point these clocks will be wrong by around 30 seconds.
The ability of a chronometer to maintain accuracy (not to drift with respect to its initial setting) has traditionally been referred to as 'going rate'. This is not the same thing as accuracy, which refers to discrepancy between actual time and represented time at a given moment. This timepiece apparently has a going rate of 1 second in 300 billion years, but its absolute accuracy will depend on how it's synchronised with absolute time at the moment it's set running. And by the way, what is absolute time anyway - once we 're talking in terms of seconds per billion years, what's the reference?
This timepiece apparently has a going rate of 1 second in 300 billion years
Is that 1 second spread uniformly across 300 billion years or say there is going to be a 1 second jump at any moment within 300 billion time period?
Imagine if you always wake up at 6:30 and that one day your alarm clock goes off at 6:29:59. That's easily the whole day ruined.
How sensitive would this be to altitude? The closer you are to the ground, the slower time passes. Also, the rotation speed of the Earth varies slightly with the global weather. Would that be something that could measureably affect the rate at which time passes for such a clock?
You can only measure time in your frame of reference. If you had 2 of these clocks, one on the ground and one atop Mt Everest they would differ but as far as the time in their frames of reference are concerned they would both be correct.
It's not just altitude but velocity too, a clock on the equator will differ from an identical one at the pole and don't start on clocks in moving vehicles such as rockets or satellites.
Plainly a standard reference is required from which all other clocks are set, historically this was a clock in Greenwich but now various standards bodies like NIST, NPL, ISO etc cooperate.
My mechanical watch runs about 3 secs per day fast. I set it 30 seconds slow on the first of the month and re-set it at the end of the month when it's running 1 minute fast. That's over a month between settings and if I need to know the time more precisely it's easy to calculate to within a few seconds based on the date. I can't think of the last time I needed to know the time with such accuracy - nothing else happens in my life that starts or finishes on time to this precision. If I were in charge of this scandiuum clock it would run for almost 900,000 years before it needed adjusting.
And I appear. Umm, yes, OK. Ata guess you need one atom to make such a clock? Which would make the lb of Sc I've got floating around in the souvenir box enough to make one for ever El Reg reader?
There's the Xmas offer sorted then.
BTW, Brexit was great, Yah?
It's easy enough to keep time by microwaves, since they can be put into an electrical circuit that connects to a clock.
And it's easy enough to measure distances with the wavelength of light, just by using an interferometer.
That's why, in the past, while the second was defined as 9,192,631,770 oscillations of a hyperfine transition in Cesium-133, the metre had been defined as 1,650,763.73 wavelengths of the spectral line associated with the 2p10 to 5d5 transition of Krypton-86.
But then they decided to keep only the second, and define the speed of light as exactly 2.99792458 * 10^8 metres per second, requiring distance to be derived from microwaves, which are more suitable to measuring time than distance. I felt this was a mistake, but maybe I'm wrong, and they have found ways to manage to get an improvement in the accuracy of the metre out of this.
Now, we would have to switch to X-Rays. Which can't be seen in an interferometer, making it hard to measure distance with them, and whose oscillations we have no way to turn into electrical pulses for counting either. So we could have a supremely accurate definition of the metre and the second, but one that is impossible to actually put to use to calibrate anything.
Right now, the particular resonance involved is known to have an energy of 12.38959 keV. This is only seven digits, and we will need to know the value of the resonance to nineteen digits to even use it as a theoretical definition to the possible accurace of one part in 10^19.
So, while it is an interesting first step, who knows how long it's going to take to fill in the missing pieces?
Oh, wait a moment. It is possible to perform X-Ray diffraction experiments. So you diffract these X-Rays from scandium with a crystal, and once you measure the angle by which they've diffracted... you have now measured the spacing between atoms in the crystal by one part in 10^19, and you can use that to calibrate something because that might actually be measurable directly. And no doubt there are other ways that scientists can figure out.
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