[time-nuts] Updating the unit of,time: the second.

[Mike Cook]

> Le 27 mai 2019 à 11:13, Dave B via time-nuts <time-nuts at lists.febo.com> a écrit :
> 
> Hi.
> 
> This from the recent ShortWave Radiogram broadcast, may be of interest.
> 
> ~ ~ ~
> 
> (Snipped stuff about other SI units undergoing a revamp...)
> 
> Scientists now have their sights set on updating the unit of
> time: the second.
> 
> Currently, the second is defined by atomic clocks made of cesium
> atoms. Those atoms absorb a certain frequency of light. The
> wiggling of the light's electromagnetic waves functions like the
> pendulum on a grandfather clock, rhythmically keeping time. One
> second is defined as 9,192,631,770 oscillations of the light.
> 
> But a new generation of atomic clocks, known as optical atomic
> clocks, outdo the cesium clocks. "Their performance is a lot
> better than what currently defines the second," says physicist
> Andrew Ludlow of the National Institute of Standards and
> Technology in Boulder, Colo. Because those optical atomic clocks
> operate at a higher frequency, their "ticks" are more closely
> spaced, making them about 100 times more precise than cesium
> clocks.
> 
> Ideally, the length of a second should be defined using the most
> precise timepieces available. A switch might happen in the late
> 2020s, Ludlow says.

I disagree with this.

a. There is no need for a new definition.
b. Any new definition would have to be realizable and easily verifiable. 
c. The first commercial cesium clocks were available in 1956, but the second did not get redefined until 1967.  There is no rush.
    I believe that commercial optical clocks are available but:
d. There are too many flavors of optical clocks around on lab benches. So despite their increased precision and stability which flavor would get the vote?

So I predict that that will be no change in the definition in the next 20 years and chip scale optical clocks will be available before five years hence.


> 
> The change to the kilogram's definition was carefully
> orchestrated so that it wouldn't affect normal people: A kilogram
> of flour still makes the same number of biscuits. Any change to
> the second will be similarly coordinated.
> 
> So, sorry, there'll be no chance to squeeze any extra seconds
> into a day.
> 
> https://www.sciencenews.org/article/kilogram-just-got-revamp-unit-time-might-be-next
> 
> ~ ~ ~
> 
> So, perhaps a host of surplus cesium clocks on the market at some point?
> 
> 73
> 
> Dave B G0WBX.
> 
> -- 
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> 
> 
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