[time-nuts] Why not TAI?

[Magnus Danielson]

On 10/08/11 09:09, cook michael wrote:
> Le 10/08/2011 07:41, Attila Kinali a écrit :
>> On Fri, 15 Jul 2011 05:57:45 +0000
>> "Poul-Henning Kamp"<phk at phk.freebsd.dk> wrote:
>>
>>> Everybody but the time-lords have always been told to stay away from
>>> TAI in the strongest possible terms by said time-lords, who again and
>>> told the world to use UTC.
>> May i ask what the reason was to stay away from TAI?
>> I mean, it is obvious (for me) that for any application that needs
>> a steady, continious and monotone clock that TAI is one of the best
>> alternatives among all those time standards.
>>
>> Attila Kinali
> There are all manner of time scales , and each has its use so there is
> no need to keep away from any. Just pick that which suits your
> application. I think that Poul-Henning was just indicating in a humorous
> manner his dislike of the unilateral imposition of a non uniform scale,
> UTC, as the transmitted time standard. So if you want a uniform scale,
> take TAI. You can get TAI from GPS time by adding 19secs. A number of
> GPS receivers can be configured to report GPS time rather than UTC.

Well, the "ban" on TAI has resulted in several "TAI-like" time-scale, 
such as the GPS time-scale (with nominally 18 second GPS-TAI difference 
as I recall it). Several such scales has been produced as a result of 
the ban. Now there is a drive to turn the UTC into one of those 
time-scales too. What is driving the use of such time-scales is however 
not political but technical, and it would have been much better if they 
would all had been using the TAI scale to start with.

Besides, SMPTE has defined the SMPTE Epoch such that all sample-rates, 
carriers etc. for TV and audio had a common phase of 0 degree at 
1958-01-01T00:00:00Z, and since then effectively follows TAI.

So, the time-lords will have to come up with a pretty good reason why 
one should not use TAI, if handwaving and just saying so is just a poor 
excuse. They should be happy that we do not use EAL, which is the 
internal time-scale.

Cheers,
Magnus