[time-nuts] Solving the UTC drift problem

David Forbes dforbes at dakotacom.net
Thu Jul 14 01:45:17 EDT 2005

A modest proposal:

Instead of adding randomly-placed leap seconds to UTC or allowing UTC 
to drift from UT1 etc, the timing community should just change the 
second's definition from time to time as needed. That is, dither the 
Cs transition frequency between 9,192,631,770 Hz or ,780 Hz annually 
to make time speed up or slow down to match the earth's rotation.

After all, that 9,192,631,770.0 Hz frequency is an arbitrary number. 
It just happened to be close to the MST-derived second in 1967, 
rounded to the nearest 10 Hz.

The beauty of this method is that there are only a few hundred Cs 
clocks in the world, and they are phase locked to 10.000 MHz or 
1.0230 MHz oscillators. Changing the PLL divisor on a few hundred Cs 
clocks by 10 Hz has got to be a lot easier than adding or subtracting 
unpredictable leap seconds from all the millions of software clocks 
in the world.

(Yes, it would be a bit of work to modify all those Cs clocks. The 
GPS satellite clocks may not currently have the ability to program 
the PLL from Earth. But those clocks will all need to replaced in a 
few years.)

All the Rb and quartz standards out there are secondary and 
disciplined to Cs clocks anyways, so they would accommodate the new 
second definition with no hardware or software changes. All the 
timekeeping software of the telecom world would get simpler.

The pulsar astronomers who require very precise absolute time units 
will be able to use the history of the Cs division ratio in their 
elapsed time calculations, and UTC will always be within a second of 
MST if the Cs frequency is dithered every year as needed.

Is this an old idea?

Am I missing something?

--David Forbes, Tucson, AZ

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