[time-nuts] Why not TAI?

cook michael michael.cook at sfr.fr
Wed Aug 10 14:35:11 UTC 2011

Le 10/08/2011 12:55, Attila Kinali a écrit :
> If TAI is a paper clock, what else should be used if a strictly monotone
> time scale is needed?
Do you have any specific application in mind?
If you need an SI seconds rated scale, then you need something based on 
TAI. GPS time has a TAI second rate and is monotonic. But of course you 
would need a GPS receiver to access it.

> And what makes UTC different from TAI to be a "real clock", as UTC is
> derived from TAI by adding leap seconds?

  I don't think TAI is any less real than UTC. UTC just happens to be 
the international transmitted time scale. TAI is not generally 
available, though both GPS time, and UTC have the same rate.

> Would a reverse definition of TAI (or rather TAI' ) by using UTC without the
> leap seconds be a good enough approximation?

Well, UTC doesn't exist without leap seconds by definition, but if you 
only have UTC available to be able to track TAI , then you can recover 
the  TAI  scale by deducting leap seconds.

> I'm quite sure i'm not the first one asking this question, but i couldn't
> find an answer, neither with google nor in the time-nuts archives.
> 			Attila Kinali

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